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Cancer is one of the leading causes of death worldwide producing estimated cost of $161.2 billion in the US in 2017 only. Early detection of cancer would not only reduce cancer mortality rates but also dramatically reduce healthcare costs given that the 17 million new cancer cases in 2018 are estimated to grow 27.5 million new cases by 2040. Analytical devices based upon paper substrates could provide effective, rapid, and extremely low cost alternatives for early cancer detection compared to existing testing methods. However, low concentrations of biomarkers in body fluids as well as the possible association of any given biomarker with multiple diseases remain as one of the greatest challenges to widespread adoption of these paper-based devices. However, recent advances have opened the possibility of detecting multiple biomarkers within the same device, which could be predictive of a patient's condition with unprecedented cost-effectiveness. Accordingly, this review highlights the recent advancements in paper-based analytical devices with a multiplexing focus. The primary areas of interest include lateral flow assay and microfluidic paper-based assay formats, signal amplification approaches to enhance the sensitivity for a specific cancer type, along with current challenges and future outlook for the detection of multiple cancer biomarkers.

Ultrathin devices are rapidly developing for skin-compatible medical applications and wearable electronics. Powering skin-interfaced electronics requires thin and lightweight energy storage devices, where solution-processing enables scalable fabrication. To attain such devices, a sequential deposition is employed to achieve all spray-coated symmetric microsupercapacitors (mu SCs) on ultrathin parylene C substrates, where both electrode and gel electrolyte are based on the cheap and abundant biopolymer, cellulose. The optimized spraying procedure allows an overall device thickness of approximate to 11 mu m to be obtained with a 40% active material volume fraction and a resulting volumetric capacitance of 7 F cm(-3). Long-term operation capability (90% of capacitance retention after 10(4) cycles) and mechanical robustness are achieved (1000 cycles, capacitance retention of 98%) under extreme bending (rolling) conditions. Finite element analysis is utilized to simulate stresses and strains in real-sized mu SCs under different bending conditions. Moreover, an organic electrochromic display is printed and powered with two serially connected mu-SCs as an example of a wearable, skin-integrated, fully organic electronic application. Funding Agencies|European Research Council (ERC) under the European Unions Horizon 2020 research and innovation programEuropean Research Council (ERC) [949191]; city council of Brno, Czech Republic

Paper-based advanced functional materials have become the focus of intense research in recent years. Particularly, magnetic papers show strong potential for applications in a wide range of 4.0 technologies including communication, magnetic sensing, electromagnetic filtering, magnetic-based health care tools, point-of-care microfluidic devices, and security. In situ and lumen-loading, the main methods to prepare magnetoactive papers, have problems such as the rigorous reaction conditions, hard control of deposition location, decreased tensile strength, poor retention of magnetic nanoparticles, or the obligation to perform the magnetic impregnation during the papermaking process, that hinder their applicability. Those issues are addressed in the present work, in which approximate to 20 nm Fe3O4 nanoparticles are hydrothermally synthesized and later incorporated in a wax-based home-made cartridge and nanoimpregnated into paper by a thermal process leading to a magnetic paper with improved stress and strain at rupture and Young's modulus, 30 MPa, 4.5%, and 2 GPa, respectively, when compared to neat paper, 15 MPa, 3.5%, and approximate to 1 GPa, respectively. Additionally, the reported magnetic impregnation method provides the paper with a 0.2 emu g(-1) magnetic saturation, allowing it to work as a bending actuator with a bending of 12 mm at an applied magnetic field of 105 mT., The authors thank the FCT- FundacAo para a Ciencia e Tecnologia- for financial support in the framework of the Strategic Funding UID/FIS/04650/2020 and under projects PTDC/BTM-MAT/28237/2017 and PTDC/EMD-EMD/28159/2017. R. B-P. acknowledges also support from FCT (SFRH/BD/140698/2018). P.M. thanks FCT- FundacAo para a Ciencia e Tecnologia for the contract under the Stimulus of Scientific Employment, Individual Support - 2017 Call (CEECIND/03975/2017). The authors thank funding by the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the project PID2019-106099RB-C43/AEI/10.13039/501100011033 and from the Basque Government Industry and Education Department under the ELKARTEK, HAZITEK and PIBA (PIBA-2018-06) programs, respectively. Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, EGEF and ESF) is gratefully acknowledged.

Porous graphene (PG) devices fabricated in situ from polyimide (PI) adhered onto paper substrates provide a cost-effective and recycling-friendly alternative to re-engineer paper for liquid-based power sources and sensors. However, paper is generally damaged due to heating during the fabrication of PG devices. Here integrated graphene-paper electronics with exceptional thermal control through the proposed thermally localized laser graphitization (LLG) process is demonstrated, employing optimized ultrafast laser writing. LLG enables in situ fabrication of localized porous graphene (LPG) devices (>1775 K) on 65 µm thick PI tape adhered to paper without heating above 348 K. Laser parameters for LLG are predicted using an analytical temperature model and validated experimentally. The LLG is demonstrated by fabricating liquid electrolyte LPG micro-supercapacitors and humidity sensors on liquid susceptible paper. It is envisaged that the scientific concepts proposed and demonstrated here will expedite the development of low-cost, scalable, and chemically robust LPG devices on thermally sensitive substrates. Ministry of Education (MOE) Funding: This work is supported under the research collaboration agreement by Panasonic Factory Solutions Asia Pacific (PFSAP) and Singapore Centre for 3D Printing (SC3DP) (RCA-15/027). V.M.M. also acknowledges the financial support received through COLE-EDB, and MOE Tier 1 Grant RG192/17. S.W.L. acknowledges the support by Academic Research Fund Tier 2 from Ministry of Education, Singapore under ref. no. 2018-T2-1-045.

Portable, on-demand micropower generation is provided by developing paper-based biobatteries that can deliver on-chip energy to the next generation of point-of-care (POC) diagnostic platforms. This work creates a low-cost, disposable, long shelf life and eco-friendly micropower source that can be easily integrated in paper-based POC devices and be readily activated by one drop of saliva, which is readily available in any challenging area. A high-performance, paper-based, bacteria-powered battery is created by building microbial fuel cells with inactive, lyophilized (or freeze-dried) exoelectrogenic cells, allowing for a long shelf life, which generates power within minutes of adding saliva. An oxygen-tight interface and engineered conductive paper reservoir achieve significant performance boosts from maximized microbial electron transfer efficiency. Exoelectrogenic bacteria preinoculated in the paper battery is freeze-dried for long-term storage (in this work, the bacteria cells are stored for up to four months) and can be readily rehydrated for on-demand power generation. Sixteen microbial fuel cells are incorporated on a single sheet of paper while all are connected in series with two electrical switches mounted on a paper circuit board, which produce more than enough electrical energy to power an on-chip, light-emitting diode.

The authors thank Swnalund Chair Professor of University of Illinois at Urbana-Champaign Prof. John Rogers for useful discussion about this paper. This publication is based upon work supported by the King Abdullah University of Science and Technology (KAUST) Office of Sponsored Research (OSR) under Award No. Sensor Innovation Initiative OSR-2015-Sensors-2707 and KAUST-KFUPM Special Initiative OSR-2016-KKI-2880. M.M.H. conceptualized and directed the study. J.M.N. led the study. K.M. developed the electronic circuit. K.L. assisted with human subject testing. A.A.A. helped with design. J.M.N. and M.M.H. coauthored the paper. Every author reviewed the final draft.

Inkjet printing (IJP) is the most widespread direct-write technique in paper electronics. However, its use is limited, since its low-viscosity nano-inks leak through the cellulose fibers. Thus, a planarization coating is frequently used as barrier, despite that this makes substrates more expensive and less ecofriendly. Alternatively, high solid content screen printing (SP) inks could allow printing on regular paper due to their high viscosity and their large particle size; however, they cannot be printed through IJP. Another digital technique is required: laser-induced forward transfer (LIFT). The aim of this work is to prove the feasibility of LIFT for printing devices on regular paper. The main transfer parameters are systematically varied to obtain uniform Ag-SP interconnects, which performance is improved by a multiple-printing approach, resulting in low resistances with a much better performance than those typical of IJP. After optimizing the printed lines functionality, a proof-of-concept consisting on a radio-frequency inductor is provided. The characterization of the device shows a substantially higher performance than that of the same device printed with IJP ink in similar conditions, which proves the potential of LIFT for digitally fabricating devices on regular paper.

For the first time, the plasma-assisted inkjet printing of metal-organic decomposition (MOD) inks is demonstrated to provide an easily up-scalable method toward the deposition of highly conductive silver features on paper. Atmospheric plasma sintering methods provide a fast and effective alternative to thermal treatment. This high-speed, room-temperature approach ensures the immediate conversion of the MOD inks after printing and thus overcomes wetting issues typically encountered in porous substrates—a mechanical solution to a chemical problem.

This manuscript describes a simple and rapid method for fabricating free-standing structures composed primarily (>94% w/w, and 55–80 at%) of noble metals (e.g., gold, silver, platinum, etc.) and having physical morphologies that resemble paper, thread, or fabric. In this method, templates (i.e., pieces of paper, or cotton fabric) are loaded with aqueous solutions of salts of noble metals, and then the cellulosic component is burned off in a furnace held at high temperatures (i.e., from 550 °C to 800 °C, depending on the procedure, in air). Even though the environment in a furnace is ostensibly oxidizing (e.g., hot air), the metal ions are reduced to elemental metal and form paper-templated or fabric-templated structures that have morphologies similar to that of the material from which they were derived (i.e., paper or fabric). Paper-templated structures are fibrous, permeable to gases and liquides, electrically conductive, and in some cases (e.g., paper-templated gold and paper-templated platinum structures), their surfaces are electroactive. The surface areas of paper-templated structures are more than 20 times higher than their projected areas. Paper-templated structures thus have properties that make them potentially useful in catalysis, sensing, and electroanalysis.

Human skin and hair can simultaneously feel pressure, temperature, humidity, strain, and flow—great inspirations for applications such as artificial skins for burn and acid victims, robotics, and vehicular technology. Previous efforts in this direction use sophisticated materials or processes. Chemically functionalized, inkjet printed or vacuum-technology-processed papers albeit cheap have shown limited functionalities. Thus, performance and/or functionalities per cost have been limited. Here, a scalable “garage” fabrication approach is shown using off-the-shelf inexpensive household elements such as aluminum foil, scotch tapes, sticky-notes, napkins, and sponges to build “paper skin” with simultaneous real-time sensing capability of pressure, temperature, humidity, proximity, pH, and flow. Enabling the basic principles of porosity, adsorption, and dimensions of these materials, a fully functioning distributed sensor network platform is reported, which, for the first time, can sense the vitals of its carrier (body temperature, blood pressure, heart rate, and skin hydration) and the surrounding environment.

The present work reports on the handwriting of electronic circuits on paper based on the deposition of an inorganic oxide semiconductor, exploiting the pen-on-paper (PoP) approach. The method relies on the use of a parallel metal plate pen, well known from calligraphy applications, which permits controlled deposition of a continuous zinc oxide (ZnO) dual-phase layer on conventional printing paper. The hand-drawn ZnO film exhibits a continuous and uniform surface with a thickness of roughly 1.5 µm, allowing the application as active layer for UV sensors and field effect transistors on paper. Photocurrent generated from the UV radiation reaches values up to 3.4 mA cm−2 with switching times on the order of few seconds. The final written paper transistors, where paper plays simultaneously the role of substrate and dielectric, reaches On/Off current ratios (IOn/IOff) of about two orders of magnitude and field effect mobility close to 5 × 10−3 cm2 V−1 s−1. As a final proof-of-concept a common source amplifier showing clear inverting characteristics is fabricated using a PoP written driving ZnO-based transistor and a pencil-drawn track as the load resistance.

Unlike traditional hard grippers, soft robotic grippers are commonly made of soft materials so that the soft grippers can produce motion via elastic deformations of their compliant components. The advantages of compliance allow soft grippers to effectively eliminate shocks caused by hard contact, which usually occurs when a hard robotic gripper manipulates a hard object. Until now, the soft robotic grippers are able to operate numerous objects with irregular geometries and different textures. Besides, with the help of embedded sensors, soft robotic grippers have facilitated the growing automation of many tasks, which are thought to be far too delicate for robotic manipulation. This paper reviews the advancement in soft robotic grippers. The paper first introduces the actuation technologies followed by the design and fabrication techniques. The use of 3D printing techniques in the fabrication of the soft gripper is also discussed. The Review then highlights the challenges and future outlook in the fabrication of soft grippers and sensors. Nanyang Technological University Submitted/Accepted version This work was partly supported by the Schaeffler Hub for Advanced Research at NTU, under the ASTAR IAF-ICP Programme ICP1900093.

To extend the preservation of donor hearts beyond the current 4-6 h, this paper explores heart cryopreservation by vitrification-cryogenic storage in a glass-like state. While organ vitrification is made possible by using cryoprotective agents (CPA) that inhibit ice during cooling, failure occurs during convective rewarming due to slow and non-uniform rewarming which causes ice crystallization and/or cracking. Here an alternative, "nanowarming", which uses silica-coated iron oxide nanoparticles (sIONPs) perfusion loaded through the vasculature is explored, that allows a radiofrequency coil to rewarm the organ quickly and uniformly to avoid convective failures. Nanowarming has been applied to cells and tissues, and a proof of principle study suggests it is possible in the heart, but proper physical and biological characterization especially in organs is still lacking. Here, using a rat heart model, controlled machine perfusion loading and unloading of CPA and sIONPs, cooling to a vitrified state, and fast and uniform nanowarming without crystallization or cracking is demonstrated. Further, nanowarmed hearts maintain histologic appearance and endothelial integrity superior to convective rewarming and indistinguishable from CPA load/unload control hearts while showing some promising organ-level (electrical) functional activity. This work demonstrates physically successful heart vitrification and nanowarming and that biological outcomes can be expected to improve by reducing or eliminating CPA toxicity during loading and unloading.

Funding: European Research Council - 819346; Engineering and Physical Sciences Research Council - EP/V029975/1; Royal Society - URF\R\211033. In this paper, the design, fabrication, and experimental demonstration of conformable holographic metasurfaces are reported. Here, it is shown that the produced holographic image changes as the metasurface is applied to targets with different shapes. The demonstration is based on a reflective type metasurface, where the reflected polarization is perpendicular to that of the incident light. In addition, how the parameters of the metasurface determine the quality of the images produced and the ability to produce independent images are discussed critically. Publisher PDF

Terrain adaptation and amphibious landing pose the greatest challenges for soft amphibious robots. Based on the principles of tortoises, this paper presents a fully 3D-printed soft amphibious robot with four pneumatic bionic legs that are capable of bending in three dimensions. The gaits of the robot are described in six different ways and a dynamic model is developed for its control. In addition to linear motion (0.97 BL s−1) and turning (25.4° s−1) on rigid terrain, the robot can also maneuver on various surface conditions (such as hills, gaps, smooth slopes, gravel, sand, muddy terrain, and water), and even make an amphibious landing. These properties, together with the soft amphibious robot's continuous obstacle avoidance capabilities, high load-carrying capacity (28 times its own weight), low cost, and high camouflage, allow for a wide variety of applications.

Magnetically-actuated soft robots for medical applications are required to be functional, biocompatible, as well as capable of robust motion inside human organs. In this paper, a ring-shaped magnetic soft robot, with a flexible biopolymeric film coating, capable of motion on mucus-coated surfaces is designed and investigated. The biopolymeric film made from chitosan–glycerol (C–G) solution endows the robot with robust locomotion capabilities on surfaces of diverse geometrical shapes and orientations. By utilizing mucoadhesive locomotion, the robot has the potential to carry out clinical procedures on enclosed mucus-coated tissue surfaces. Material characterization shows that the mucoadhesion increases with the increase of contact times and/or preload forces. The softness of the C–G film can be adjusted by controlling the concentration of glycerol. The ring-shaped design and magnetization profile decouple the locomotion and functions of the robot. Additionally, the C–G film-coated robot is tested to be biocompatible for a human colorectal adenocarcinoma cell line with epithelial morphology (HT29). The C–G film reduces the negative effects (superoxide generation) of ferromagnetic particles. Three robot functions including pick-and-place, cargo transportation, and liquid capsule release are demonstrated on different surfaces to show the maneuverability, functionality, and potential of implementing clinical procedures through mucoadhesion.

Bioelectronic medicine can treat diseases and disorders in humans by electrically interfacing with peripheral nerves. Multielectrode cuffs can be used for selective stimulation of portions of the nerve, which is advantageous for treatment specificity. The biocompatibility and conformability of cuffs can be improved by reducing the mechanical mismatch between nerve tissue and cuffs, but selective stimulation of nerves has yet to be achieved with soft and stretchable cuff electrodes. Here, this paper reports the development of a soft and stretchable multielectrode cuff (sMEC) for selective nerve stimulation. The device is made of 50 mu m thick silicone with embedded gold nanowire conductors, which renders it functional at 50% strain, and provides superior conformability for wrapping nerves. By using different stimulation protocols, high functional selectivity is achieved with the sMECs eight stimulation electrodes in a porcine sciatic nerve model. Finite element modeling is used to predict the potential distribution within the nerve, which correlate well with the achieved stimulation results. Recent studies are showing that mechanical softness is of outermost importance for reducing foreign body response. It is therefore believed that the soft high-performance sMEC technology is ideal for future selective peripheral nerve interfaces for bioelectronic medicine. Funding Agencies|Swedish Foundation for Strategic Research; Swedish Research Council [2019-04424]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoeping University (Faculty Grant SFO Mat LiU) [2009 00971]; European Research Council, "e-NeuroPharma" ERC-2018-ADG [834677]

Wearable sensors are emerging as a new technology to detect physiological and biochemical markers for remote health monitoring. By measuring vital signs such as respiratory rate, body temperature, and blood oxygen level, wearable sensors offer tremendous potential for the noninvasive and early diagnosis of numerous diseases such as Covid‐19. Over the past decade, significant progress has been made to develop wearable sensors with high sensitivity, accuracy, flexibility, and stretchability, bringing to reality a new paradigm of remote health monitoring. In this review paper, the latest advances in wearable sensor systems that can measure vital signs at an accuracy level matching those of point‐of‐care tests are presented. In particular, the focus of this review is placed on wearable sensors for measuring respiratory behavior, body temperature, and blood oxygen level, which are identified as the critical signals for diagnosing and monitoring Covid‐19. Various designs based on different materials and working mechanisms are summarized. This review is concluded by identifying the remaining challenges and future opportunities for this emerging field., Wearable sensors have demonstrated grand potential for remote health monitoring recently, particularly after the Covid‐19 pandemic. The need for wearable telehealth systems capable of monitoring vital signs, such as respiratory rate, body temperature, and blood oxygen level has surged. In this review, the recent advances in creating these sensors and remaining challenges as well as prospects are presented.

In this paper, a full textile capacitive woven sensor integrated over a textile substrate is presented. The sensor consists in an interdigitated capacitance prepared to measure moisture and/or presence detection. In order to evaluate the sensor response to moisture, capacitance has been measured by means of an LCR meter from 20 Hz to 20 kHz in a climatic chamber with a swept of the relative humidity (RH) from 30% to 90% at 20 °C. Subsequently, presence response is evaluated measuring the capacitance of the woven sensor meanwhile a person is sitting down and getting up. The woven sensor results demonstrate its functionality over moisture measurement where sensor capacitance changes from a minimum of 9.74 pF at 30% RH to a maximum of 2.31 uF at 90% RH. The presence detection is also demonstrated, which makes the capacitance variation change from a 10% of capacitance variation when the chair is empty, to a capacitance variation of 170% when a person is sitting on it. The adaptation of the weaving process to accomplish a fully integrated sensor provides a better repeatability than previous embroidered sensors and opens a door to being commercially produced. This work was supported by Spanish Government-MINECO under Project TEC2016-79465-R and AGAUR-UPC(2020 FI-B 00028). Agencia de Gestión de Ayudas Universitarias y de Investigación, Generalitat de Catalunya.

Printed magnetic field sensors enable a new generation of human-machine interfaces and contactless switches for resource-efficient printed interactive electronics. As printed magnetoresistors rely on scarce or hard to manufacture magnetosensitive powders, their scalability and demonstration of printing with industry-grade technologies are the key material science challenges. Here, the authors report dispenser printing of a commodity scale nonmagnetic bismuth-based paste processed by large area laser sintering to obtain printed magnetoresistive sensors. The sensors are printed on different substrates including ceramics, paper, and polymer foils. It is validated experimentally that the peculiar quantum large orbital magnetoresistive effect remains effective in printed bismuth sensors, allowing their operation in high magnetic fields. The sensors reveal up to 146% resistance change at 5 T at room temperature with a maximum resolution of 2.8 mu T. If printed on flexible foils, these sensors show resilience to bending deformation for more than 2000 bending cycles and withstand even thermal forming, as relevant for smart wearables and in-mold electronics. The freedom in the substrate choice and sensor design enabled by dispenser printing allows to implement the proposed sensor technology for different applications focused on touchless interactive platforms, such as advertisement materials, interactive wallpapers, and printed security panels.

In this work, a novel glucose quantification strategy is presented in a self-powered biosensing device. The analyte in the sample is oxidized in an enzymatic fuel cell and the generated charge is transferred to a capacitor. The built-up capacitor voltage at a specific time can be directly correlated with the concentration of analyte. An electro-fluidic switch placed on a paper-based microfluidic channel connects a minimalistic electronic circuit to the fuel cell. The circuit modules discriminate the built-up capacitor voltage, which corresponds to a particular glucose range. The digital semi-quantitative result is visualized vía electrochromic displays. As a practical application of this working principle, the self-powered single-use device has been designed to perform screening of gestational diabetes mellitus. The device discriminates between healthy (7.8 mm), and diabetes (>11.1 mm) condition providing a reliable result. This single use, printable, and disposable self-powered glucose biosensing device is autonomous and fully powered by the glucose contained in a 3.5 µL sample. It offers an energy-saving, environmentally friendly, and low-cost solution for Point-of-Care testing. By replacing the selective enzyme in the fuel cell, this strategy can be used for measuring other health parameters such as creatinine, cholesterol, or uric acid, among others.

Electrically controllable deoxyribonuclic acid (DNA) nanolevers are used to investigate the binding interaction between Influenza A/Aichi/2/1968 and the peptide called “PeB”, which specifically binds the viral surface protein hemagglutinin. PeB is immobilized on gold electrodes of a “switchSENSE” biochip by conjugation to DNA-strands that are hybridized to complementary anchors. The surface-tethered DNA strand carries a fluorophore while the complementary strand is a multivalent arrangement carrying up to three PeB peptides. The nanolevers are kept upright (static) by applying a negative potential. Signal read-out for this static measurement mode is the change in fluorescence intensity due to changes in the local environment of the dye upon binding. Measurements of virus-peptide interaction show that the virus material specifically binds to the immobilized peptides and remains bound throughout the measurement time. Immobilized viruses are subsequently used as ligands to characterize oligovalent peptide binding to hemagglutinin, revealing rate constants of the interaction. Moreover, three Influenza A subtypes are compared in their binding behavior. Overall, this paper shows the ability to immobilize virus material on a sensor surface, which allows to target virus-proteins in their native environment. The “switchSENSE” method is therefore applicable to characterize virus-receptor interactions.

There is a significantly increasing demand on developing a microLED (μLED) based microdisplay which may be the only display system that can meet the requirements for augmented reality/virtual reality systems, helmet mounted displays, and head‐up displays. However, a number of fundamental challenges which cannot be met by any existing technologies need to be overcome before such a microdisplay with satisfied performance becomes possible. In this paper, a different type of integration concept using an epitaxial approach is proposed, aiming to monolithically integrate μLEDs and high electron mobility transistors (HEMTs) on a single chip. This concept can be potentially realized by using a selective epitaxial overgrowth method on a predefined HEMT template featuring microhole masks. Finally, the proposed epitaxial integration concept is translated into a prototype, demonstrating an 8 × 8 microLED microdisplay, where each μLED is electrically driven by an individual HEMT which surrounds its respective μLED via the gate bias of the HEMT.

Surface electromyography (sEMG) allows for direct measurement of electrical muscle activity with use in fundamental research and many applications in health and sport. However, conventional surface electrode technology can suffer from poor signal quality, requires careful skin preparation, and is commonly not suited for long-term recording. These drawbacks have challenged translation of sEMG to clinical applications. In this paper, dry 3D-printed microneedle electrodes (MNEs) are proposed to overcome some of the limitations of conventional electrodes. Employing a direct-metal-laser-sintering (DMLS) 3D printing process, a two-step fabrication method is developed to produce sharp medical-grade stainless steel MNEs. The developed MNEs are compared to needle-free versions and to standard wet Ag/AgCl electrodes. Functional testing is conducted to analyze the electrode–skin impedance in healthy human volunteers and sEMG data are recorded from the biceps brachii muscle. Results show that microneedle electrodes display a greatly reduced (≈63%) electrode–skin contact impedance with respect to needle-free electrodes and record sEMG at a signal-to-noise ratio comparable to clinical-grade wet Ag/AgCl electrodes over a period of up to 6 h. Overall, a fabrication method and electrode type are presented which yield high-quality sEMG signals when evaluated in humans, highlighting the potential of MNEs as a platform for biosignal recording. European Commission Horizon 2020 Irish Research Council National University of Ireland Travel Studentship

This paper describes a type of haptic device that delivers two modes of stimulation simultaneously and at the same locations on the skin. The two modes of stimulation are mechanical (delivered pneumatically by inflatable air pockets embedded within a silicone elastomer) and electrical (delivered by a conductive polymer). The key enabling aspect of this work is the use of a highly plasticized conductive polymer based on poly(3,4-ethylenedioxythiphene) (PEDOT) blended with elastomeric polyurethane (PU). To fabricate the “electropneumotactile” device, the polymeric electrodes are overlaid directly on top of the elastomeric pneumatic actuator pockets. Co-placement of the pneumatic actuators and the electrotactile electrodes is enabled by the stretchability of the PEDOT:OTs/PU blend, allowing the electrotactiles to conform to underlying pneumatic pockets under deformation. The blend of PEDOT and PU has a Young’s modulus of ~150 MPa with little degradation in conductivity following repeated inflation of the air pockets. The ability to perceive simultaneous delivery of two sensations to the same location on the skin are supported by experiments using human subjects. These results show that participants can successfully detect the location of pneumatic stimulation and whether electrotactile stimulation is delivered (yes/no) at a rate significantly above chance (mean accuracy = 94%).

Here, an environmentally-friendly and scalable process is reported to synthesize reduced graphene oxide (RGO) thin films for printed electronics applications. The films are produced by inkjet printing GO flakes dispersed binder-free in aqueous solutions followed by treatment with a nonthermal, radio-frequency (RF) plasma containing only argon (Ar) gas. The plasma process is found to heat the substrate to temperatures no greater than 138 °C, enabling RGO to be printed directly on a wide range of temperature-sensitive substrate materials including photo paper. Unlike other low-temperature methods such as electrochemical reduction, plasma reduction is friendly to moisture absorbent materials. Moreover, the plasma treatment can be performed on nonconducting substrates, eliminating the need for film transfer. From an applications perspective, the printed, plasma-reduced RGO exhibits excellent electrical, mechanical, and electrochemical properties. As a technology demonstrator, the working electrodes of hydrogen peroxide (H(2)O(2)) sensors fabricated from plasma-reduced GO show a sensitivity of 277 ± 80 μA mm(−1) cm(−2), which is comparable to RGO working electrodes made by electrochemical reduction.

Li-ion batteries (LIBs) dominate the energy storage market owing to their versatility and efficient energy storage. Also, for electric vehicle applications, batteries with better power, safety, and cyclability are needed. To address the issues related to lower power density, lesser cyclability, low capacity retention, safety, cost, etc., several modifications like nanostructuring, 3D and 2D architectures, doping, core shell particles, binder free electrodes, modified electrolytes, and separators are employed. Plasma technologies can reduce the number of steps and time required for the synthesis of nanoarchitectures and material modifications, hence a reduction in the cost required to produce LIBs against the high initial investment required. This review paper aims at emphasizing plasma enabled modification and synthesis techniques for LIB electrodes, separators, electrolytes, and for recent advances like solid state and flexible batteries.

Acoustically-responsive microbubbles have been widely researched as agents for both diagnostic and therapeutic applications of ultrasound. Recently, there has also been considerable interest in magnetically functionalised microbubbles as multi-modality imaging agents and carriers for magnetically targeted drug delivery. The latter application in particular requires simultaneous application of magnetic and acoustic fields to a target region. This can present a significant practical challenge, especially in vivo where access is typically limited. In this paper, we present a design for an integrated device capable of generating co-aligned magnetic and acoustic fields in order to accumulate microbubbles at a specific location and then to activate them acoustically. For the purposes of this proof of concept study, the magnetic component of the device was designed to concentrate microbubbles at a distance of 10 mm from the probe’s surface, commensurate with relevant tissue depths in preclinical small animal models. The ultrasound transducer was designed to maximise the acoustic intensity in the same region in order to induce cavitation of the magnetically captured microbubbles. Previous studies have indicated that both microbubble concentration and duration of cavitation activity are positively correlated with therapeutic effect. The ability of the device to trap and activate microbubbles was therefore assessed by a series of in vitro tests in a tissue mimicking phantom containing a single vessel of 1.2 mm diameter. At a flow rate of 4.2 mm/s magnetic trapping produced an increase in intensity under B-mode ultrasound imaging consistent with the predicted accumulation profile. When the microbubbles were exposed to the ultrasound field from the probe, the resulting cavitation activity was sustained for a period more than 4 times longer than that achieved with an identical acoustic field but in the absence of a magnet. The feasibility of developing a larger scale device for human applications is discussed.

This paper reports on a simple and versatile method for patterning and transferring graphene-based nanomaterials onto various types of tape to realize flexible microscale sensors. The method involves drop-casting a graphene film on a prepatterned polydimethylsiloxane (PDMS) surface containing negative features by graphene suspensions, applying Scotch tape to remove the excess graphene from the nonpatterned areas of the PDMS surface, and then transferring the patterned graphene from the inside of the negative features at the PDMS surface onto a target tape. The feature size of transferred graphene patterns on the final tape is as small as a few micrometers. This method is easy to implement, but does not require the use of expensive equipment, except for needing a PDMS substrate containing negative features. This method has a high versatility in producing micropatterns of graphene-based nanomaterials on different types of adhesive tape. For the purpose of application demonstration, flexible mechanical sensors and sensor arrays, smart gloves, and plant leaf sensors on tapes to realize real-time monitoring of important signals indicating human motion and plant water transport behavior have been developed. This technology will open a new route for low-cost, scalable, and roll-to-roll production of graphene-based sensors on tape.

A hybrid manufacturing paradigm is introduced that combines pop-up book microelectromechanical systems (MEMS) manufacturing with soft-lithographic techniques to produce millimeter-scale mechanisms with embedded sensing and user-defined distributed compliance. This method combines accuracy, flexibility in material selection, scalability, and topological complexity with soft, biocompatible materials and microfluidics, paving the way for applications of soft fluid-powered biomedical robotics. This paper proposes two classes of fully soft fluidic microactuators and two integration strategies to demonstrate the hybrid soft pop-up actuators. Fatigue properties, blocked torque, maximum deflection, stiffness, and maximum speed are analyzed and the performance of the hybrid mechanisms is compared to their fully soft counterparts. The manufacturing approach allows integrating capacitive sensing elements in the mechanisms to achieve proprioceptive actuation. Multiple hybrid soft pop-up actuators are combined into a multiarticulated robotic arm that is integrated with current flexible endoscopes to improve distal dexterity and enable tissue retraction in an ex vivo proof of concept experiment.

This paper demonstrates the methods that allow the fabrication of the hemispherical organic photodiode arrays on curved concave glass substrate. They include a novel 3D shadow mask, fabricated by additive manufacturing process (stereolithography), used for the electrode deposition and 3D shaped polydimethylsiloxane stamp used for organic active layer formation. These techniques allow the direct patterning of the organic photodiode devices on hemispherical substrates without an excessive strain or deformation. It is believed that the developed 3D mask and 3D organic layer transfer printing process can be further utilized for fabrication of various optoelectronic devices which necessitate a free form factor on arbitrary substrates.

This paper presents design and batch manufacturing of a highly stretchable textile-silicone capacitive sensor to be used in human articulation detection, soft robotics, and exoskeletons. The proposed sensor is made of conductive knit fabric as electrode and silicone elastomer as dielectric. The batch manufacturing technology enables production of large sensor mat and arbitrary shaping of sensors, which is precisely achieved via laser cutting of the sensor mat. Individual capacitive sensors exhibit high linearity, low hysteresis, and a gauge factor of 1.23. Compliant, low-profile, and robust electrical connections are established by fusing filaments of micro coaxial cable to conductive fabric electrodes of the sensor with thermoplastic film. The capacitive sensors are integrated on a reconstructed glove for monitoring finger motions.

Wearable sensing technology is an emerging area and can be utilized for human motion monitoring, physiology monitoring, and human–machine interaction. In this paper, a new manufacturing approach is presented to create highly stretchable and soft capacitance-based strain sensors. This involves a rapid surface modification technique based on direct-write laser rastering to create microstructured surfaces on prestrained elastomeric sheets. Then, to impart conductivity, sputtering technology is utilized to deposit aluminum and silver metal layers on the bottom and top surfaces of the elastomer sheet, creating a soft capacitor. During benchtop characterization of the sensors, this study demonstrates that the fabricated electrodes maintain their electrical conductivity up to the 250% strain, and the sensor shows a linear and repeatable output up to 85% strain. Finally, their potential is demonstrated for monitoring human motion and respiration through their integration into a wearable arm sleeve and a thoracic belt, respectively.

Research paper: Marco Carlotti*, Omar Tricinci, Virgilio Mattoli*, Novel, High-Resolution, Subtractive Photoresist Formulations for 3D Direct Laser Writing based on Cyclic Ketene Acetals, Advanced Materials Technologies,2101590, 2022 (In Press)