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Disability has been redefined by the World Health Organization as a function of a person’s interaction with the environment and not merely an innate part of a person. This redefinition highlights the need for inclusiveness in design solutions. To aid this, we apply and test the potential of different tools that restrict designers’ physical abilities at deriving inclusive design perspectives among designers. Various tools and simulated conditions are often adopted in user-centered design to sup-port need-finding by eliciting rich data on users’ needs and guide designers to empathize with users. Simulation tools that restrict designers’ physical abilities have been applied to understand certain perspectives of people with physical challenges, yet these tools lack the ability to evoke an inclusive design perspective among designers. Through a co-creation workshop, participants were exposed to two forms of simulations: direct and situational physical impairments. This was achieved using different tools that simulate the same physical restriction. In this study, a noise- canceller and earphones were used to simulate a reduced hearing attention. Participants were asked to generate user needs and design functions by applying both the simulation tools. The study results comprise the outcomes of 33 participants who volunteered to participate in a co-design workshop that provided a venue for them to interact and work alongside users with physical challenges. This paper analyses the inclusiveness attained through different types of simulated conditions. With a growing need to create tools and technologies that delight the user, it is necessary to equip designers with the tools that would help them with the process. The study demonstrates the application and impact of one such tool.

Abstract The aesthetics of a product is critical to its desirability, and can be described in terms of syntactics and semantics. Syntactic aesthetics is an objective description based on the form and configuration of a product, while semantic aesthetics is a subjective interpretation of the form and gestalt of a product. This study seeks to identify a set of syntactic attributes to describe form and understand if an individual’s preferences for a form are consistent from one product to another. Form attributes from previous literature were expanded upon to create a consistent vocabulary for syntactic aesthetics that can be used to describe multiple products. Combinations of four selected attributes are utilized to describe a diverse set of designs for two products: vases and canopies. Conjoint analysis is used to quantitatively measure the form preferences of individuals towards different combinations of attribute levels of the objects. Results from conjoint analysis applied to vase and canopy designs indicate a 61.3% consistency of individual form preferences between the products. It is hoped that this methodology can help designers develop aesthetically consistent products that align with users’ preferences by quantifying users’ aesthetic preferences towards products through a vocabulary for syntactic attributes.

Ultralight architected materials enabled by advanced manufacturing processes have achieved densitynormalized strength and stiffness properties that are inaccessible to bulk materials. However, the majority of this work has focused on static loading and elastic-wave propagation. Fundamental understanding of the mechanical behavior of architected materials under large-deformation dynamic conditions remains limited, due to the complexity of mechanical responses and shortcomings of characterization methods. Here, we present a microscale suspended-plate impact testing framework for three-dimensional (3D) micro-architected materials, where supersonic microparticles to velocities of up to 850 m/s are accelerated against a substrate-decoupled architected material to quantify its energy dissipation characteristics. Using ultra-high-speed imaging, we perform in situ quantification of the impact energetics on two types of architected materials as well as their constituent nonarchitected monolithic polymer, indicating a 47% or greater increase in mass-normalized energy dissipation under a given impact condition through use of architecture. Post-mortem characterization, supported by a series of quasi-static experiments and high-fidelity simulations, shed light into two coupled mechanisms of energy dissipation: material compaction and particle-induced fracture. Together, experiments and simulations indicate that architecture-specific resistance to compaction and fracture can explain a difference in dynamic impact response across architectures. We complement our experimental and numerical efforts with dimensional analysis which provides a predictive framework for kinetic-energy absorption as a function of material parameters and impact conditions. We envision that enhanced understanding of energy dissipation mechanisms in architected materials will serve to define design considerations towards the creation of lightweight impact-mitigating materials for protective applications.

Growing food demand, climate change, and constrained natural resources create the need for large-scale, sustainable agricultural intensification. Despite drip irrigation’s ability to be more water efficient than traditional irrigation technologies, its adoption and retention is limited to due to its high hydraulic equipment costs, particularly in low/middle-income countries. As a commodity product, drip emitters contribute directly to raw material costs and additionally dictate tube thickness and related material consumption. This work introduces a new empirical, deterministic design theory for creating compact, low-cost labyrinths, which are otherwise a volume-intensive component of drip irrigation emitters. To simplify design analysis a review of current commercial art, manufacturing process constraints and symmetry-based geometric relationships was conducted, resulting in the labyrinth’s tooth tip gap being selected as a key design variable. The tip gap is correlated with the hydraulic performance of a test labyrinth geometry via a Design of Experiments approach. The experiments shed light on two distinct fluid dynamic regimes in the labyrinth based on the tip gap size and provide an empirical expression between the two. This work demonstrates that simultaneous consideration of symmetry, manufacturing process and design goals enables rapid synthesis of labyrinths that are 43.77% shorter than comparable commercial designs.

AbstractEngineering design often requires engaging with users, clients, and stakeholders of products and systems. It is therefore important for designers to reflect on the societal and environmental implications of their design work so that they can design equitably, ethically, and justly. We conduct a review of three leading scholarly engineering design publications to investigate how, when, and why these terms—“ethics,” “equity,” and “justice,” and variations—appear in the engineering design literature and what scholars mean when they use them. We find that these terms are minimally present within the field's scholarship and posit that design researchers may be using other terms to refer to their work that is aligned with principles of ethics, equity, and justice. We find that the prevalence of these terms has increased over time and that the terms come up throughout various stages of the design process. There appear to be a variety of motivations for including these terms, notably, sustainability and education of the next generation of designers. Finally, we propose an expanded design justice framework that is specific to engineering design. We encourage designers in our field to adopt this framework to assist them in thinking through how their engineering design work can be used to advance justice.

Abstract A novel, high-performance, cosmetic, rugged, appropriately costed, and mass-manufacturable prosthetic foot for use in low-income countries was designed and field tested. This ruggedized foot was created to accommodate the unique economic, environmental, and cultural requirements for users in India. A previous prototype that enabled able-bodied like gait was modified to include a durable cosmetic cover without altering the tuned stiffness of the overall foot. After undergoing mechanical benchtop testing, the foot was distributed to prosthesis users in India to for at least 5 months. Afterward, participants underwent clinical tests to evaluate walking performance, and additional benchtop testing was performed on the field-tested feet to identify changes in performance. The ruggedized foot endured 1 × 106 fatigue cycles without failure and demonstrated the desired stiffness properties. Subjects walked significantly faster (0.14 m/s) with the ruggedized foot compared to the Jaipur foot, and the feet showed no visible sign of damage after months of use. Additionally, the field-tested feet showed little difference in stiffness from a set of unused controls. Anecdotal feedback from the participants indicated that the foot improved their speed and/or walking effort, but may benefit from more degrees-of-freedom about the ankle. The results suggest that the foot fulfills its design requirements; however, further field testing is required with more participants over a longer period to make sure the foot is suitable for use in developing countries.

As populations increase and freshwater supplies decrease, adopting water- and energy-efficient irrigation practices is crucial, particularly in resource-constrained regions. Here, farmers are often unable to purchase the equipment used in precision irrigation, a practice that implements the automatic scheduling of irrigation events to achieve high efficiency. Currently, no irrigation methods exist that combine the automatic scheduling of irrigation events with the manual operation of valves, a common practice on low-income farms. This work introduces a design concept for an automatic scheduling and manual operation (AS-MO) tool that addresses the efficiency needs of resource-constrained farms and integrates into current manual practices. However, it is unknown how farmers would value such a tool. Through interviews and focus groups facilitated by a series of storyboards and a physical prototype, the proposed concept was evaluated by farmers and key market stakeholders in Kenya, Jordan, and Morocco. Results showed that farmers in Kenya and Jordan in particular valued the proposed AS-MO concept because they want increased efficiency on their farms but did not want to install automatic valves for cost and complexity concerns. A possible market was also found in Morocco, but a majority of interviewed farms preferred automatic valve operation due to large farm sizes. Interviewees provided feedback on how to improve the tool’s design in future iterations. If adopted at scale, this AS-MO tool could increase efficiency on farms that otherwise cannot afford current precision irrigation technology, improving sustainable agriculture worldwide.

AbstractTraditionally, in the oil and gas industry, accelerometers are mounted externally on motors for condition monitoring of vertically suspended, closed suction hydrocarbon pumps due to their inability to withstand harsh downhole environments, preventing the detection of impeller failures. This study addresses the need for encapsulation solutions for accelerometers submerged in hydrocarbon fluid environments. It evaluates the feasibility of epoxy and fluoroelastomer as encapsulation materials for long-term immersion in high-temperature hydrocarbon fluid and determines their impact on the accelerometer's performance. Extensive testing involved submersion in high-temperature hydrocarbon fluid at 150 °C for over 10,000 h and six months in brine. Material characterization, including mass variation, microscopic imaging, and FTIR spectroscopy, revealed negligible degradation. Encapsulated accelerometers effectively detected vibrations with an acceptable alteration in amplitude. In comparison with commercial alternatives, our encapsulation outperformed them. While oil traces became evident within just 24 h in the alternatives, our solution exhibited no signs of leakage. This research pioneers a novel packaging solution employing epoxy and fluoroelastomer for side-exit commercial sensors tailored for high-temperature hydrocarbon fluid applications, addressing a critical gap in the industry. Our work enhances reliability and safety for vertical oil pump condition monitoring in downhole applications, benefiting the oil and gas sector.

Low and middle income countries often do not have the infrastructure needed to support weather forecasting models, which are computationally expensive and often require detailed inputs from local weather stations. Local, low-cost weather prediction services are needed to enable optimal irrigation scheduling and increase crop productivity for rural farmers in low-resource settings. This work proposes a machine learning approach to predict the weather inputs needed to calculate crop water demand, namely evapotranspiration and precipitation. The focus of this work is on the accuracy with which Moroccan weather can be predicted with a vector autoregression (VAR) model compared to using typical meteorological year (TMY) weather, and how this accuracy changes as the number of weather parameters is reduced.

Abstract There is an urgent need to provide ways to help a fast-growing older adult population to maintain daily mobility. A great deal of work exists in medical devices and robotics to generate effective assistive solutions, yet at the same time, limits have been observed in the adoption of such systems. In this paper we explore possible factors in adoption from a user-centered design perspective. We investigated user needs surrounding the act of standing up from a seated position and older users’ attitudes toward assistive device prototypes. Older adults completed a standard timed-up-and-go mobility assessment, rated their own difficulty standing, participated in interviews, and shared responses to “look-and-feel” prototypes, all in an effort to uncover latent needs. A licensed physical therapist rated videos of the subjects while standing up and the two ratings were compared. While the physical therapist’s rating of difficulty increased as subjects’ performance on the clinical mobility assessment worsened, subjects’ self-ratings did not significantly correlate with mobility performance, even when timed-up-and-go performance indicated a risk of falling. Subjects expressed preferences for potential assistive devices that were more discreet, lightweight, and flexible over devices that were bulkier, heavier, and rigid. In general, subjects’ attitudes toward assistive devices for their own sit-to-stand use were similar regardless of their demonstrated need. The results highlight the challenges designers may face when creating products for older adult users and underline the importance of a user-centered design process. Implications for assistive technology design are discussed.

Abstract Digital tools for sketching, such as tablets, have become popular for streamlining design work and keeping a large quantity of sketches in one place. However, their impact on design creativity, novelty, and concept evolution is not yet well understood. Here, we present a controlled human subjects study that assesses the influence of tablets (iPads) on concept novelty and evolution in the context of an engineering design concept generation exercise. We expect that iPad use will not influence concept novelty due to its similar speed of use as pen and paper sketching. We expect to see different patterns in concept evolution between the two types of tools, namely, that iPad users will demonstrate more iteration on a concept (concept evolution) than pen and paper users due to the fact that iPad features make it easy to copy and paste previous sketches and then modify them. We find that the tool used is not correlated with concept novelty. Additionally, we find no strong differences in overall concept evolution quantities between the two tools, though we see that iPad sketches exhibited more cases of consecutive concept evolution than nonconsecutive whereas paper and pen sketches showed an equal amount of both consecutive and nonconsecutive concept evolution. Results indicate that overall, iPads may not significantly inhibit designers’ creative skills and thus could be a reasonable replacement for pen and paper sketching, which has implications for both design education and practice.

Abstract Sketching is an important tool for engineers during concept generation. Sketch quantity during this early stage of design has been linked with eventual design outcomes and sketch quality has been linked with design perceptions. As such, both are important metrics to track. Prior work has also found gender differences in some of these sketch attributes. Given the increase in use of digital tablets for sketching, it is important to assess how tablet use affects early stage engineering design sketches. This is especially important as tablets can automatically smooth lines and help perfect sketch features, but these features may also take longer to use and may result in fewer sketches produced. This study investigates differences in sketch quality, quantity, and understandability (the effectiveness of the sketch as a communication tool) between sketching on a tablet and sketching with pen on paper during an engineering design concept generation exercise. Results indicate that there is no difference in sketch quantity or understandability between the two tools. However, sketch quality, smoothness, and proportion/accuracy are all higher for the pen and paper condition than for the tablet condition. Finally, no gender differences in performance for either sketch quantity or quality were found.

AbstractService design has been an emerging transdisciplinary field that includes product, system, and social science, since the term was first introduced to academic research in the early 1990s. With socioeconomical shifts and emerging technologies, people have faced more complex and systemic challenges, which enable researchers to consider how to reapply service design not only as problem-solving tools but also as ways for communication and alignment to adapt to the change. The study focuses on the paradigm shifts of service from its definitions to applications by interviewing nine design experts from academia and industry, and utilizing survey results to help us explore applying service design to solve complicated social-technological challenges. We present four takeaways: 1) a new understanding of service design, 2) the purpose of using service design tools, 3) the evaluation of service quality through time, and 4) the applications of service design in the public sector. We proposed a macro-trend model with service systems: product, service, and experience to conclude 1) constructing service systems in the macro-trend context and 2) gaining holistic views and building service implementation capability in the era of transformations.

In conventional classification, soft robots feature mechanical compliance as the main distinguishing factor from traditional robots made of rigid materials. Recent advances in functional soft materials have facilitated the emergence of a new class of soft robots capable of tether-free actuation in response to external stimuli such as heat, light, solvent, or electric or magnetic field. Among the various types of stimuli-responsive materials, magnetic soft materials have shown remarkable progress in their design and fabrication, leading to the development of magnetic soft robots with unique advantages and potential for many important applications. However, the field of magnetic soft robots is still in its infancy and requires further advancements in terms of design principles, fabrication methods, control mechanisms, and sensing modalities. Successful future development of magnetic soft robots would require a comprehensive understanding of the fundamental principle of magnetic actuation, as well as the physical properties and behavior of magnetic soft materials. In this review, we discuss recent progress in the design and fabrication, modeling and simulation, and actuation and control of magnetic soft materials and robots. We then give a set of design guidelines for optimal actuation performance of magnetic soft materials. Lastly, we summarize potential biomedical applications of magnetic soft robots and provide our perspectives on next-generation magnetic soft robots.

With over 30 million people worldwide requiring assistive devices, there is a great need for low-cost and high-performance prosthetic technologies that can enable kinematics close to able-bodied gait. Low-income users of prosthetic knees in the developing world repeatedly report the need for n inconspicuous gait to mitigate the severe socioeconomic discrimination associated with disability. However, passive prosthetic knees designed for these users have primarily focused on stability and affordability, often at the cost of the high biomechanical performance that is required to replicate able-bodied kinematics. In this study, we present the design and preliminary testing of two distinct mechanism modules that are novel for passive prosthetic knee applications: the stability module and the damping module. These mechanisms are designed to enable users of single-axis, passive prosthetic knees to walk with close to able-bodied kinematics on level-ground, specifically during the transition from the stance phase to the swing phase of the gait cycle. The stability module was implemented with a latch mounted on a virtual axis of a four-bar linkage, which can be engaged during early stance for stability and disengaged during late stance to initiate knee flexion. The damping module was implemented with a concentric stack of stationary and rotating pairs of plates that shear thin films of high-viscosity silicone oil. The goal of the resulting first-order damping torque was to achieve smooth flexion of the prosthetic knee within the able-bodied gait range (64 ± 6 deg). For preliminary user-centric validation, a prototype prosthetic knee with the stability module and two different dampers (with varying damping coefficients) was tested on a single subject with above-knee amputation in India. The stability module enabled smooth transition from stance to swing with timely initiation of knee flexion. The dampers also performed satisfactorily, as the increase in the damping coefficien

Food insecurity in East Africa (EA) is exacerbated by the effects of climate change. Water scarcity and high energy costs make it difficult for farmers to increase their yields to levels needed to feed growing populations. One way for countries to sustainably increase food production is to increase the adoption of water- and energy-efficient irrigation technology. Solar-powered drip irrigation systems are such a technology. These systems provide many benefits to farmers who have been able to install them on their fields, but their high costs is one barrier that currently limits its adoption among the majority of EA farmers. In this work, a concept for a novel irrigation controller is introduced and assessed for its viability in the EA market. The proposed controller determines complex irrigation schedules based on local weather predictions and specifics of a given farm. It does this while optimizing for the lifetime performance of the irrigation system, something that existing controllers do not do and something that could lower the lifetime costs of solar-powered drip irrigation systems. The proposed controller communicates this complex schedule to farmers in a way that allows them to continue to use low-cost, manually-operated valves on their fields. This concept is evaluated through storyboard-based interviews with EA farmers and key market stakeholders. The results provide initial positive feedback from these lead users, suggesting that this controller could be a viable product in EA. If adopted at scale, this technology could help lower the barrier to adopting water- and energy-efficient irrigation, ultimately having a positive, sustainable impact on food security in EA.

Abstract Engineering designers often span knowledge boundaries when developing complex systems but doing so poses challenges because members of different knowledge groups must bridge their language, cognitions, and “thought worlds” to effectively broker, resituate, and make use of each other’s ideas. Objects — ranging from prototypes to kanban boards to value stream maps — are frequently used in cross-functional design practice, but the outcomes associated with such objects appear varied and dependent not only the objects’ characteristics but on how, when, and by whom they are used. This paper describes a two-year inductive ethnographic study within a turbomachinery design company to understand how cross-functional design teams span their knowledge boundaries to advance their designs and design processes. We collected observations of 70 cross-functional meetings and 52 interviews across functional groups during the development of complex turbomachinery products. Our findings include three roles of objects of collaboration: routinizing cross-boundary interaction, translating information across boundaries, and motivating joint negotiation or discovery. We found two prominent outcomes — co-discovery of a design risk, opportunity, or workflow bottleneck and co-design of a joint integrated solution — that appeared to follow from the latter two roles, respectively. These findings are significant because they clarify the roles of objects in cross-boundary design work and suggest ways for designers to more effectively use objects to span knowledge boundaries.

Advances in robotic technology have been adopted in various subspecialties of both open and minimally invasive surgery, offering benefits such as enhanced surgical precision and accuracy with reduced fatigue of the surgeon. Despite the advantages, robotic applications to endovascular neurosurgery have remained largely unexplored because of technical challenges such as the miniaturization of robotic devices that can reach the complex and tortuous vasculature of the brain. Although some commercial systems enable robotic manipulation of conventional guidewires for coronary and peripheral vascular interventions, they remain unsuited for neurovascular applications because of the considerably smaller and more tortuous anatomy of cerebral arteries. Here, we present a teleoperated robotic neurointerventional platform based on magnetic manipulation. Our system consists of a magnetically controlled guidewire, a robot arm with an actuating magnet to steer the guidewire, a set of motorized linear drives to advance or retract the guidewire and a microcatheter, and a remote-control console to operate the system under real-time fluoroscopy. We demonstrate our system’s capability to navigate narrow and winding pathways both in vitro with realistic neurovascular phantoms representing the human anatomy and in vivo in the porcine brachial artery with accentuated tortuosity for preclinical evaluation. We further demonstrate telerobotically assisted therapeutic procedures including coil embolization and clot retrieval thrombectomy for treating cerebral aneurysms and ischemic stroke, respectively. Our system could enable safer and quicker access to hard-to-reach lesions while minimizing the radiation exposure to physicians and open the possibility of remote procedural services to address challenges in current stroke systems of care.

Abstract System Engineering education typically includes content to help students learn to design and engineer large, complex systems in a structured way. In this paper, we describe the outcomes of introducing a human-centered design tool, the Inspiration Design Toolkit (IDT), to encourage students to think non-linearly. The IDT is an educational resource consisting of a deck of illustrated cards that contain provocative questions, reflection messages and icons, applicative examples, and key takeaways on microlearning units. The aim of the IDT is to improve the participants’ learning experience and course engagement, increase opportunities for them to interact with their peers and teaching team, enable them to practice and reinforce the concepts through the creation of their own IDT cards, and share the cards in the discussion to increase learners’ engagement with course material and peers. We designed the IDT for an MIT online course on System Thinking. We collected, analyzed, and synthesized qualitative and quantitative feedback from 171 course participants. Our findings suggest that IDT provides learners with a digital asset that allows them to reinforce and recall the course takeaways, and apply them to other contexts. For future research, we want to understand how learners like and use IDT through demographic differences and preferred self-identified learning styles. We discuss how these findings may help educators consider critical design principles and for creating a digital self-learning toolkit connected to the course content and increasing its content adaptability.

Despite the rapid advances in autonomous guidance and navigation techniques for unmanned aerial vehicle (UAV) systems, there are still many challenges in finding an optimal path planning algorithm that allows outlining a collision-free navigation route from the vehicle’s current position to a goal point. The challenges grow as the number of UAVs involved in the mission increases. Therefore, this work provides a comprehensive systematic review of the literature on the path planning algorithms for multi-UAV systems. In particular, the review focuses on biologically inspired (bio-inspired) algorithms due to their potential in overcoming the challenges associated with multi-UAV path planning problems. It presents a taxonomy for classifying existing algorithms and describes their evolution in the literature. The work offers a structured and accessible presentation of bio-inspired path planning algorithms for researchers in this subject, especially as no previous review exists with a similar scope. This classification is significant as it facilitates studying bio-inspired multi-UAV path planning algorithms under one framework, shows the main design features of the algorithms clearly to assist in a detailed comparison between them, understanding current research trends, and anticipating future directions. Our review showed that bio-inspired algorithms have a high potential to approach the multi-UAV path planning problem and identified challenges and future research directions that could help improve this dynamic research area.

Abstract Within higher education, there are increasing calls for design-focused fields, such as engineering and urban planning, to incorporate social, policy, and ethical considerations into their courses to create and develop more responsible, society-minded designers to solve today’s complex societal issues. At the same time, not all instructors of design courses may feel equipped or comfortable engaging social, policy, and ethical considerations in their courses. Previous work has shown that engineering courses engage less with these considerations than other design fields. More perspectives are necessary to understand how instructors consider engaging these considerations and their motivations behind it. We present a survey of instructors regarding their curricular practices and goals as they relate to social, policy, and ethical considerations to understand the barriers, resources, and changes of these considerations in design education. Our results demonstrate there is an increased awareness for the need for this type of content that is promising for the future of engaging social, policy, and ethical considerations in design curriculum. However, for those instructors interested in including such considerations there are barriers such as the identifiable relevance, lack of time and educational materials inhibiting their inclusion. This can be supported by more educational resources, financial support, and prioritization in design education.

Hygroscopic hydrogels are emerging as scalable and low‐cost sorbents for atmospheric water harvesting, dehumidification, passive cooling, and thermal energy storage. However, devices using these materials still exhibit insufficient performance, partly due to the limited water vapor uptake of the hydrogels. Here, the swelling dynamics of hydrogels in aqueous lithiumchloride solutions, the implications on hydrogel salt loading, and the resulting vapor uptake of the synthesized hydrogel–salt composites are characterized. By tuning the salt concentration of the swelling solutions and the cross‐linking properties of the gels, hygroscopic hydrogels with extremely high salt loadings are synthesized, which enable unprecedented water uptakes of 1.79 and 3.86 gg−1 at relative humidity (RH) of 30% and 70%, respectively. At 30% RH, this exceeds previously reported water uptakes of metal–organic frameworks by over 100% and of hydrogels by 15%, bringing the uptake within 93% of the fundamental limit of hygroscopic salts while avoiding leakage problems common in salt solutions. By modeling the salt‐vapor equilibria, the maximum leakage‐free RH is elucidated as a function of hydrogel uptake and swelling ratio. These insights guide the design of hydrogels with exceptional hygroscopicity that enable sorption‐based devices to tackle water scarcity and the global energy crisis.

Sporopollenin is a mechanically robust and chemically inert biopolymer that constitutes the outer protective exine layer of plant spores and pollen grains. Recent investigation of the molecular structure of pine sporopollenin revealed unique monomeric units and inter-unit linkages distinct from other previously known biopolymers, which could be harnessed for new material design. Herein, we report the bioinspired synthesis of a series of sporopollenin analogues. This exercise confirms large portions of our previously proposed pine sporopollenin structural model, while the measured chemical, thermal, and mechanical properties of the synthetic sporopollenins constitute favorable attributes of a new kind of robust material. This study explores a new design framework of robust materials inspired by natural sporopollenins, and provides insights and reagents for future elucidation and engineering of sporopollenin biosynthesis in plants.

We report the central role of mechanical contraction in healing of wounds in animal models, as well as in humans. Our evidence has been collected from studies of excised skin wounds as well as with the transected peripheral neve and the excised conjunctiva. We have observed that, following blocking of contraction, wounds in our animal models close by regeneration of the injured tissues. We review the mechanism of contraction blocking and tissue regeneration when wounds are grafted with a highly porous Type I collagen scaffold, named dermis regeneration template (DRT) which is required for inducing regeneration.

AbstractDesign and engineering are socio-technical enterprises used to solve real-world problems. However, students in these fields are often under-equipped to consider the ethical and societal implications of their work. Our prior work showed that these societal considerations are more consistently embedded in design pedagogy in non-engineering than in engineering courses at MIT. Here, we examine underlying causes for this through a survey of instructors (231 courses from 29 departments). The main contribution of this work is an analysis of whether and how instructors incorporate social, ethical, and policy considerations in design pedagogy. The majority of respondents (60.6%) included these topics in their courses, primarily through discussion of social justice, identity groups, and ethics. These concepts were included more in non-engineering courses (65.8%) than engineering courses (46.9%). Many instructors, especially in engineering, cited irrelevance as the reason for not engaging with these topics in their courses (86.1% compared to 44.2% in non-engineering). We suggest that instructors question this perception and use the examples provided as a starting point to explore integration of these concepts into their technical content.

Hardware-based startups risk having longer times-to-market, deterring investment in the clean technologies that are critical to a sustainable future. We interviewed 55 leaders at hardware startups, 20 of which are cleantech, mapped their development timelines, and found prototyping to be the longest development step (median of 19 weeks per prototype) regardless of prototype complexity or iteration. Qualitative interview analysis reveals the prototyping team’s choice of development style is a major factor affecting timeline. We define two development styles: natural and structured, typified by free-form exploration and rule-based execution, respectively. On average, natural development takes 35% less time than structured, and is thus preferred for early iterations, but adopting structure at strategic points is needed for timely commercialization. Critical points of transition to a structured style include adding new team members or engaging external partners, which demand clear communication and expectations. When pivoting to a new product or market, returning to a natural style is beneficial.

There is significant need for low-cost, high-performance prosthetic knees in low- and middle-income countries (LMICs) due to a large number of amputees and particularly challenging socioeconomic and environmental conditions. Prostheses are important for maintaining one’s participation in society, culture, and the economy, but many are either prohibitively expensive or do not provide near-able-bodied kinematics. Poor performing prosthetic knees cause discomfort and draw unwanted attention to transfemoral amputees. In this study, we refine the design of a high-performing, single-axis, passive prosthetic knee developed with a focus on the Indian market in order to reduce cost, weight, and part count; enhance manufacturability; and improve aesthetics. The load paths and functional componentry were critically analyzed to identify opportunities to streamline the design while maintaining strength and the near-able-bodied kinematics offered by the original design. The part count was reduced almost four-fold, and the mass of the prosthesis was reduced three-fold. An enclosure was also designed to encase the functional componentry in an aesthetically acceptable package. The changes made to the design are believed to significantly advance the usability and commercial viability of the prosthetic knee. This study may serve as an example of how products developed for emerging markets may achieve affordability without sacrificing performance.

Strain-induced crystallization (SIC) prevalently strengthens, toughens, and enables an elastocaloric effect in elastomers. However, the crystallinity induced by mechanical stretching in common elastomers (e.g., natural rubber) is typically below 20%, and the stretchability plateaus due to trapped entanglements. We report a class of elastomers formed by end-linking and then deswelling star polymers with low defects and no trapped entanglements, which achieve strain-induced crystallinity of up to 50%. The deswollen end-linked star elastomer (DELSE) reaches an ultrahigh stretchability of 12.4 to 33.3, scaling beyond the saturated limit of common elastomers. The DELSE also exhibits a high fracture energy of 4.2 to 4.5 kJ m −2 while maintaining low hysteresis. The heightened SIC and stretchability synergistically promote a high elastocaloric effect with an adiabatic temperature change of 9.3°C.

Reactive multilayers are energetic nanostructures that are able to deliver a large amount of chemical energy via an exothermic reaction. These materials have been a subject of growing interest as they have been shown to provide effective local heat delivery for microscale propulsion or biological hazard neutralization. Nonetheless, their use as heat sources remains narrow because of the limits in tuning their intrinsic reactivity without altering their architecture. Here, we propose a method for the adjustment of reaction kinetics in Ni/Al multilayers via solid solution alloying with elements having different reactivities toward aluminum. Nickel layers were alloyed with copper and platinum, resulting in strong modification of the properties of the heat front, temperature, and propagation velocity, while at the same time leaving the multilayer architecture unaltered. This effect hails from a shift in the rate limiting mechanism during intermixing of the reacting species that promotes the propagation of the reaction. The results of this study will expand the field of application of reactive multilayers as integrated heat sources, thermal batteries, or microheaters.

Water scarcity is increasingly becoming a problem in India, so much so that a recently proposed piece of legislation would mandate home-scale water desalination systems to have a 60% recovery ratio [1], significantly higher than existing systems. We developed an electrodialysis-based home-scale desalination system for obtaining drinking water that will meet and surpass this new proposed recovery ratio. This project builds heavily on previous and current work by the MIT Global Engineering and Research (GEAR) Lab and was conducted with Eureka Forbes Limited (EFL), a major stakeholder in India’s home-scale desalination industry. Two critical design modules within the desalinator are explored — the system integration and fluid reversal mechanism and the electrodialysis stack end cap analysis. We developed a model framework that will output the validity of end cap designs based on established design requirements, designed fluid reversal mechanisms for distinct markets, and fabricated a prototype desalination cabinet that fits within the EFL’s design constraints. We also discuss the details of our collaboration with both academic and industrial partners, extract specific lessons learned about the lab-to-market design process, and discuss some of the specific challenges faced by a design group in our circumstances and the ways we resolved them.

AbstractThe purpose of the study is to understand the design considerations for creating a provocative financial planning toolkit with services to help facilitate more constructive and meaningful conversations to build trust and empathy between financial advisors and senior people. We conducted four rounds of 60-minute co-creation workshops with eight invited participants from various design disciplines to work in pairs to generate four preliminary concepts suggesting design considerations. We used ATLAS.ti to do qualitative research analysis under an NCT (notice, collecting, thinking) model to identify 22 codes synthesized from verbal and behavioral data. The study concluded with three design principles: 1) the concept of financial planning is about people's expectation management, 2) a financial planning toolkit is designed under service systems, and 3) the tailor-made and modular design features can give financial advisors more flexibility to engage with senior people and enable them to share more about their life stories and needs to recommend financial planning packages precisely according to personal preference, health conditions, and financial status.

Abstract Sketching is often used as a tool during idea generation in the early stages of engineering design. At the same time, the rapid increase in remote engineering and design work paves the way for an increased reliance on digital design tools and technologies throughout the design process. Sketch quality and quantity have been shown to be linked to design perceptions and design outcomes. Additionally, sketch quality and style have been linked with the gender of the sketcher. Thus, there are financial, social, and ethical motivations for understanding how digital design tools influence sketching during early stages of engineering design. In this study, we investigate the influence of hand sketching on a tablet as compared to pencil or pen and paper on early stage sketching for concept generation. We also assess the influence of gender on sketching attributes. We ask three mixed gender groups of participants (using pen, pencil, and a tablet) to sketch concepts in response to an open-ended design prompt. We hypothesize that participants using tablet and pencil will produce fewer drawings than those using pen due to their ability to erase and focus on perfecting drawings, and we expect participants using the tablet to produce cleaner drawings with smoother strokes due to the tablet’s ability to auto-smooth lines. Based on prior literature, we posit that women and gender minorities will produce fewer sketches and use the feathering style of sketching more than men. We find that sketch quality is highest for pencil drawings and lower for tablet and pen drawings. We also find that concept novelty is negatively correlated with how understandable the concept is. Participants reported that experiences of drawing on paper and on the tablet differ in terms of missing the feeling of friction on the tablet and finding that too many features in a tool can be distracting during concept generation. Interestingly

Tissue adhesives are promising alternatives to sutures and staples for joining tissues, sealing defects, and immobilizing devices. However, existing adhesives mostly take the forms of glues or hydrogels, which offer limited versatility. We report a direct-ink-write 3D printable tissue adhesive which can be used to fabricate bioadhesive patches and devices with programmable architectures, unlocking new potential for application-specific designs. The adhesive is conformable and stretchable, achieves robust adhesion with wet tissues within seconds, and exhibits favorable biocompatibility. In vivo rat trachea and colon defect models demonstrate the fluid-tight tissue sealing capability of the printed patches, which maintained adhesion over 4 weeks. Moreover, incorporation of a blood-repelling hydrophobic matrix enables the printed patches to seal actively bleeding tissues. Beyond wound closure, the 3D printable adhesive has broad applicability across various tissue-interfacing devices, highlighted through representative proof-of-concept designs. Together, this platform offers a promising strategy toward developing advanced tissue adhesive technologies.

Marine animals equipped with sensors provide vital information for understanding their ecophysiology and collect oceanographic data on climate change and for resource management. Existing methods for attaching sensors to marine animals mostly rely on invasive physical anchors, suction cups, and rigid glues. These methods can suffer from limitations, particularly for adhering to soft fragile marine species such as squid and jellyfish, including slow complex operations, unreliable fixation, tissue trauma, and behavior changes of the animals. However, soft fragile marine species constitute a significant portion of ocean biomass (>38.3 teragrams of carbon) and global commercial fisheries. Here we introduce a soft hydrogel-based bioadhesive interface for marine sensors that can provide rapid (time <22 s), robust (interfacial toughness >160 J m−2), and non-invasive adhesion on various marine animals. Reliable and rapid adhesion enables large-scale, multi-animal sensor deployments to study biomechanics, collective behaviors, interspecific interactions, and concurrent multi-species activity. These findings provide a promising method to expand a burgeoning research field of marine bio-sensing from large marine mammals and fishes to small, soft, and fragile marine animals.

AbstractThe spontaneous formation of biological substances, such as human organs, are governed by different stimuli driven by complex 3D self-organization protocols at the molecular level. The fundamentals of such molecular self-assembly processes are critical for fabrication of advanced technological components in nature. We propose and experimentally demonstrate a promising 3D printing method with self-healing property based on molecular self-assembly-monolayer principles, which is conceptually different than the existing 3D printing protocols. The proposed molecular building-block approach uses metal ion-mediated continuous self-assembly of organic molecular at liquid–liquid interfaces to create 2D and 3D structures. Using this technique, we directly printed nanosheets and 3D rods using dithiol molecules as building block units.

Abstract There is a growing movement in engineering and industry for students and practitioners to learn to embrace failure and develop resilience. The design process is naturally full of iteration and failures that can inherently be leveraged as learning opportunities for students. This study establishes a set of failure-related interventions implemented in an introductory design course, and then examines potential links to students’ experiences and attitudes towards failure. These interventions included a failure-themed “speaker seminar” series, a virtual gallery of design mistakes (“mistake museum”), and the introduction of a prototype logger for students to intentionally reflect on each iteration of their own design projects, including what went wrong and what was learned from the iteration. Students found these interventions to be effective in gaining perspective on failure and learning to embrace it. Students’ perceptions of the openness to failure of the class, perceptions of the field of design’s openness to failure, and perceptions of their major’s openness to failure all changed significantly, while their perceptions of their own openness to failure and their academic institution’s openness to failure were unchanged over the duration of the design course. Students also self-reported that the reflective processes of logging prototypes made them feel more comfortable with failure.

Abstract Designers routinely create informal “thinking” sketches to explore a design space, “talking” sketches to communicate design ideas during the early phases of the design process, and “learning” prototypes to test potential concepts. This study presents two new tools to assess novice designers’ sketch attributes and prototyping reflections in the context of an introductory design course. First, it proposes a rubric for assessing the quality of early-stage design sketches including line smoothness, proportion, and understandability. Of particular note is the contribution of assessing understandability as a metric for sketches as communication tools. This study also presents a tool to capture designer reflections after each iteration of a prototype. Not only does this record what is learned about a design but also designers’ personal and emotional reactions to the process. Sketching-related results show a positive correlation between sketch quality and understandability, indicating the importance of sketch quality especially when designers use sketches to communicate. Results also indicate that early-stage sketch quantity, but not quality, is linked with design outcomes. This study also finds a link between the frequency of sketching and higher maximum sketch quality scores (i.e., at least one highly rated sketch) as well as a correlation between individuals’ maximum sketch quality scores and overall design outcomes. Preliminary results around prototyping indicate that reflection on both the technical and emotional aspects of prototyping may be a worthwhile area of further study. Finally, several results point to novice designers’ lack of consistent focus on users in their prototyping reflections and presentations.

Abstract Engineering design often requires engaging with users, clients, and stakeholders of products and systems. It is therefore important for designers to reflect on the societal and environmental implications of their design work so that they can design equitably, ethically, and justly. We conduct a review of three leading scholarly engineering design venues to investigate how, when, and why these terms — “ethics,” “equity,” and “justice,” and variations — appear in the engineering design literature and what scholars mean when they use them. We find that these terms are minimally present within the field’s scholarship and posit that design researchers may be using other terms to refer to their work that is aligned with principles of ethics, equity, and justice. We find that the prevalence of these terms has increased over time and that the terms come up throughout various stages of the design process. There appear to be a variety of motivations for including these terms, notably, sustainability and education of the next generation of designers. Finally, we propose an expanded design justice framework that is specific to engineering design. We encourage designers in our field to adopt this framework to assist them in thinking through how their engineering design work can be used to advance justice.

AbstractThe walking pattern and comfort of a person with lower limb amputation are determined by the prosthetic foot’s diverse set of mechanical characteristics. However, most design methodologies are iterative and focus on individual parameters, preventing a holistic design of prosthetic feet for a user’s body size and walking preferences. Here we refined and evaluated the lower leg trajectory error (LLTE) framework, a novel quantitative and predictive design methodology that optimizes the mechanical function of a user’s prosthesis to encourage gait dynamics that match their body size and desired walking pattern. Five people with unilateral below-knee amputation walked over-ground at self-selected speeds using an LLTE-optimized foot made of Nylon 6/6, their daily-use foot, and a standardized commercial energy storage and return (ESR) foot. Using the LLTE feet, target able-bodied kinematics and kinetics were replicated to within 5.2% and 13.9%, respectively, 13.5% closer than with the commercial ESR foot. Additionally, energy return and center of mass propulsion work were 46% and 34% greater compared to the other two prostheses, which could lead to reduced walking effort. Similarly, peak limb loading and flexion moment on the intact leg were reduced by an average of 13.1%, lowering risk of long-term injuries. LLTE-feet were preferred over the commercial ESR foot across all users and preferred over the daily-use feet by two participants. These results suggest that the LLTE framework could be used to design customized, high performance ESR prostheses using low-cost Nylon 6/6 material. More studies with large sample size are warranted for further verification.

Abstract Designers routinely create informal “thinking” sketches to explore a design space and “talking” sketches to communicate design ideas during the early phases of the design process. This study proposes a rubric for assessing the quality of novice designers’ early stage design sketches including line smoothness, proportion, and understandability. The study finds a positive correlation between sketch quality and understandability, which indicates the importance of sketch quality when using sketches as a communication tool. Results indicate that early stage sketch quantity is linked with design outcomes, though sketch quality does not have a strong correlation with design outcomes. The study also finds a link between frequency of sketching and having higher maximum sketch quality scores (i.e. at least one excellent sketch) as well as a correlation between individuals’ maximum sketch quality scores and their overall design outcomes. This study presents a new tool to capture what is learned by the designer after each iteration of a prototype. Preliminary results indicate that reflection on both the technical and emotional aspects of prototyping may be valuable and should be an area of further study. Finally, several results point to novice designers’ lack of consistent focus on users in their prototyping reflections and presentations.

People with lower-limb amputation in low- and middle-income countries (LMICs) lack access to adequate prosthetic devices that would restore their mobility and increase their quality of life. This is largely due to the cost and durability of existing devices. Single-keel energy storage and return (ESR) prosthetic feet have recently been developed to provide improved walking benefits at an affordable cost in LMICs. These low-cost single-keel ESR feet were created using a novel design methodology, the lower leg trajectory error (LLTE) framework. The LLTE framework enables the optimization of the stiffness and geometry of a user’s prosthesis to match a target walking pattern. However, these low-cost single-keel ESR prostheses do not provide the required durability to fulfill the international standards organization (ISO) testing, which prevents their widespread use and adoption. In this work, we developed a multi-keel prosthetic foot parametric model, and extended the LLTE framework to include this multi-keel architecture and the durability requirements. This extended LLTE framework enabled the design of durable and low-cost multi-keel ESR prosthetic feet made of Nylon 6/6. Multi-keel foot designs were shown to provide 76% improved walking performance (lower LLTE values) compared with single-keel ESR designs. Load testing of prototype multi-keel feet validated the multi-keel constitutive model predictions used in the LLTE framework. The measured deflections of the prototypes under load were accurately described with an average error of 0.6 ± 0.4 mm (5.7 ± 4.2%). These multi-keel feet designed using the extended LLTE framework withstood ISO fatigue and static tests, validating their durability. Given their single-part 2D extruded geometries, multi-keel feet designed with the extended LLTE framework could be cost-effectively manufactured, providing affordable and durable high-performance prostheses that improves the mobility of LMIC users.

AbstractGlobally, 1.6 billion people in rural regions face water scarcity. Expanding freshwater access via brackish groundwater desalination can provide additional resources to address this challenge. In this study, we have developed a time-variant electrodialysis reversal (EDR) technology that flexibly uses available solar energy for desalination. Our proposed photovoltaic-powered desalination system can vary pumping and EDR power to match the availability of intermittent solar power, maximizing the desalination rate. Our results show improved system performance with the direct use of 77% of available solar energy—91% more than in conventional systems—and a 92% reduction in battery reliance. In a village-scale desalination case study in India, these system improvements lead to a 22% reduction in water cost, making the technology competitive with the currently used on-grid, village-scale reverse osmosis systems that are mainly powered by fossil fuels. Future advances could further reduce costs, providing an improved, sustainable solution to water scarcity in remote areas.

We introduce neural lithography to address the ‘design-to-manufacturing’ gap in computational optics. Computational optics with large design degrees of freedom enable advanced functionalities and performance beyond traditional optics. However, the existing design approaches often overlook the numerical modeling of the manufacturing process, which can result in significant performance deviation between the design and the fabricated optics. To bridge this gap, we, for the first time, propose a fully differentiable design framework that integrates a pre-trained photolithography simulator into the model-based optical design loop. Leveraging a blend of physics-informed modeling and data-driven training using experimentally collected datasets, our photolithography simulator serves as a regularizer on fabrication feasibility during design, compensating for structure discrepancies introduced in the lithography process. We demonstrate the effectiveness of our approach through two typical tasks in computational optics, where we design and fabricate a holographic optical element (HOE) and a multi-level diffractive lens (MDL) using a two-photon lithography system, showcasing improved optical performance on the task-specific metrics. The source code for this work is available on the project page: https://neural-litho.github.io.

AbstractGenerative design tools empowered by recent advancements in artificial intelligence (AI) offer the opportunity for human designers and design tools to collaborate in new, more advanced modes throughout various stages of the product design process to facilitate the creation of higher performing and more complex products. This paper explores how the use of these generative design tools may impact the design process, designer behavior, and overall outcomes. Six in-depth interviews were conducted with practicing and student designers from different disciplines who use commercial generative design tools, detailing the design processes they followed. From a grounded theory-based analysis of the interviews, a provisional process diagram for generative design and its uses in the early-stage design process is proposed. The early stages of defining tool inputs bring about a constraint-driven process in which designers focus on the abstraction of the design problem. Designers will iterate through the inputs to improve both quantitative and qualitative metrics. The learning through iteration allows designers to gain a thorough understanding of the design problem and solution space. This can bring about creative applications of generative design tools in early-stage design to provide guidance for traditionally designed products.

Humanitarian crises ranging from political unrest to natural disasters are becoming increasingly prevalent with global climate change. Correspondingly, there are an increasing number of regions that consist both of high crises risk and saline water contamination. Such regions include the Middle East, Subsaharan Africa (particularly along the Great Rift Valley), Southeast Asia (including the Mekong Delta and Pacific Islands), and coastal regions. However, there is a lack of robust, deployable desalination technologies for humanitarian crises. This is mainly attributed to the highly-constrained environment which necessitate: minimization of consumables, rapid speed of deployment and simplification of operation and maintenance. Such constraints are often secondary thoughts, are difficult to traditionally quantify, and differ from stable commercial situations where operations are supported by an accessible supply chain and network of technicians. These barriers have particularly hindered the adoption of membrane technology and thus, high volume desalination and chemical contaminant removal. This work justifies the need for desalination technology in humanitarian crises via geospatial analysis of saline water databases and exploration of regional case studies, formulates design requirements for an emergency-use desalination system based on needs extracted from open-interviews of stakeholders and literature review, evaluates some of the gaps within currently employed deployable desalination systems and explores the potential opportunities of other desalination technology.

AbstractDevelopments in artificial intelligence (AI) are opening the possibilities for the development of more advanced design tools. An example of these innovations are generative design tools, in which the generation of complex and high performing products is possible. This study investigates the use of generative design tools and how they may influence the design process and designer behaviour. Six interviews of interdisciplinary designers were conducted to understand the implications of using generative design tools. It was observed that generative design tools primarily allow for quantitative inputs to the tool while qualitative metrics, such as aesthetics, are considered indirectly by designers. The subjectivity of the designer and how they incorporate the quantitative and qualitative metrics in the generative design tool can lead to differing outcomes between designers. Notable differences in tool usage are also observed between expert and novice computational designers. Additional studies should be conducted to further understand the extent generative design tools impact the design process, designer behaviour, and design outcomes.

Acute liver failure (ALF) is a critical medical condition defined as the rapid development of hepatic dysfunction. Conventional ultrasound elastography cannot continuously monitor liver stiffness over the course of rapidly changing diseases for early detection due to the requirement of a handheld probe. In this study, we introduce wearable bioadhesive ultrasound elastography (BAUS-E), which can generate acoustic radiation force impulse (ARFI) to induce shear waves for the continuous monitoring of modulus changes. BAUS-E contains 128 channels with a compact design with only 24 mm in the azimuth direction for comfortable wearability. We further used BAUS-E to continuously monitor the stiffness of in vivo rat livers with ALF induced by d -galactosamine over 48 hours, and the stiffness change was observed within the first 6 hours. BAUS-E holds promise for clinical applications, particularly in patients after organ transplantation or postoperative care in the intensive care unit (ICU).

Abstract Spanning knowledge group boundaries is both a source of and barrier to design performance and innovation. Objects—from prototypes to kanban boards—are frequently used in cross-functional design practice, but their associated outcomes appear varied and dependent not only on the objects themselves but on how, when, and by whom they are used. We conducted a two-year ethnography within a turbomachinery design company to understand how professional engineering designers span knowledge group boundaries to advance their designs and design processes. Our findings identify three roles of objects of collaboration: routinizing cross-boundary interaction, translating information across boundaries, and motivating joint negotiation or discovery. We illustrate two prominent outcomes—the co-discovery of a design risk, opportunity, or bottleneck and the co-design of a joint integrated solution—and describe two object role sequences from which these outcomes seem to follow. These findings are significant because they suggest ways for designers to effectively use objects to span knowledge group boundaries.

People with lower-limb amputation in low- and middle-income countries (LMICs) lack access to adequate prosthetic devices that would restore their mobility and increase their quality of life. This is largely due to the cost and durability of existing devices. Single-keel energy storage and return (ESR) prosthetic feet have recently been developed using the lower leg trajectory error (LLTE) design framework to provide improved walking benefits at an affordable cost in LMICs. The LLTE framework optimizes the stiffness and geometry of a user’s prosthesis to match a target walking pattern by minimizing the LLTE value, a measure of how closely a prosthetic foot replicates a target walking pattern. However, these low-cost single-keel prostheses do not provide the required durability to fulfill International Standards Organization (ISO) testing, preventing their widespread use and adoption. Here, we developed a multi-keel foot parametric model and extended the LLTE framework to include the multi-keel architecture and durability requirements. Multi-keel designs were shown to provide 76% lower LLTE values, compared with single-keel designs while withstanding ISO fatigue and static tests, validating their durability. Given their single-part 2D extruded geometries, multi-keel feet designed with the extended LLTE framework could be cost-effectively manufactured, providing affordable and durable high-performance prostheses that improve the mobility of LMIC users.

Advances in understanding the effects the mechanical characteristics of prosthetic feet on user biomechanics have enabled passive prostheses to improve the walking pattern of people with lower limb amputation. However, there is no consensus on the design methodology and criteria required to maximize specific user outcomes and fully restore their mobility. The Lower Leg Trajectory Error (LLTE) framework is a novel design methodology based on the replication of lower leg dynamics. The LLTE value evaluates how closely a prosthetic foot replicates a target walking pattern. Designing a prosthesis that minimizes the LLTE value, optimizes its mechanical function to enable users to best replicate the target lower leg trajectory. Here, we conducted a systematic sensitivity investigation of LLTE-optimized prostheses. Five people with unilateral transtibial amputation walked overground at self-selected speeds using five prototype energy storage and return feet with varying LLTE values. The prototypes' LLTE values were varied by changing the stiffness of the participant's LLTE-optimized design by 60%, 80%, 120%, and 167%. Users most closely replicated the target able-bodied walking pattern with the LLTE-optimized stiffness, experimentally demonstrating that the predicted optimum was a true optimum. Additionally, the predicted LLTE values were correlated to the user's ability to replicate the target walking pattern, user preferences, and clinical outcomes including roll-over geometries, trunk sway, prosthetic energy return, and peak push-off power. This study further validates the use of the LLTE framework as a predictive and quantitative tool for designing and evaluating prosthetic feet.