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This paper presents the design, fabrication, calibration, and implementation of a novel stretchable array of capacitive sensors that mimics human receptors for an esophageal swallowing robot. The array is used to measure deformation of the esophageal conduit wall and the interaction between food bolus and the esophagus in the form of pressure and shear stress, which is a novel in vitro method of food bolus transport study. It is constructed from a thin sheet of copper-polyimide laminate via a cost effective fabrication process involving photolithography, wet etching, and laser engraving technique. Calibration is conducted individually on the pressure, shear, and strain sensor elements of the array. The pressure, shear, and strain sensors response exhibit an average hysteresis of 10.17%, 11.78%, and 26.37% caused by the soft silicon rubber encapsulation. Linear regression technique is used to determine the linear sensitivity transfer function for all the three sensors. The array is embedded beneath the surface of the esophageal conduit of the swallowing robot and a series of swallowing experiments are conducted. Three types of food bolus with a viscosity of 0.18, 0.62, and $1.55~\text {Pa}\cdot \text {s}$ are prepared using a commercial food thickener. The swallowing robot generates a peristaltic wave of 60-mm wavefront length and 40- $\text {mm}\cdot \text {s}^{-1}$ wave speed to mimic the swallowing action seen in the human esophagus. Manometer measurements are taken alongside for validation. The pressure sensor records maximum pressures of 2.24, 3.17, and 7.74 kPa, respectively, for the three types of bolus during swallowing. By comparison, the maximum pressures recorded by the manometer are 1.68, 2.82, and 8.08 kPa. The shear sensor on the other hand records maximum shear values of −0.3, −0.35, and −0.37 kPa, respectively, for the three food bolus mixtures. This works prove that the novel stretchable array of capacitive sensors can be used to mimic mechanoreceptors for the esophageal swallowing robot, which significantly extends its capability to be used by food scientists as a platform for a new novel method of bolus transport study.

Characterization, modeling, and control of pneumatic artificial muscles is typically demonstrated in an antagonistic architecture. There are many conflicting design constraints when designing these systems, resulting in many different styles of testing apparatus. A novel, systematic design methodology is proposed to improve these architectural constraints and describe the envelope of possible system outputs in terms of displacement and torque/force. It is founded upon a mathematical expression of actuator-model convolution. The proposed systematic antagonistic design by convolution (SADC) method involves three steps. First, model the workspace capability of each fluidic muscle. Second, devise the physical layout of the antagonistic apparatus by convolution, which investigates the structure for output workspace dexterity. Finally, establish trajectories and control, which is left to the application engineer. This method reduces the focus on the actuator capability, and instead represents a general method to approach system-level specification and design. The new SADC methodology facilitates design for a larger symmetric force capability. It is demonstrated for two cases, a symmetric and an asymmetric antagonistic system. It contributes a new pathway to explore optimization of antagonistic workspace symmetry at a system level and aids the engineer in visualizing architectural tradeoffs. It is independent of the application's control methodology and can be modified to examine alternative cost functions that require optimization.

This paper presents the design, fabrication, and characterization of a multimodal sensor with integrated stretchable meandered interconnects for uniaxial strain, pressure, and uniaxial shear stress measurements. It is designed based on a capacitive sensing principle for embedded deformable sensing applications. A photolithographic process is used along with laser machining and sheet metal forming technique to pattern sensor elements together with stretchable grid-based interconnects on a thin sheet of copper polyimide laminate as a base material in a single process. The structure is embedded in a soft stretchable Ecoflex and PDMS silicon rubber encapsulation. The strain, pressure, and shear stress sensors are characterized up to 9%, 25 kPa, and ±11 kPa of maximum loading, respectively. The strain sensor exhibits an almost linear response to stretching with an average sensitivity of −28.9 fF%−1. The pressure sensor, however, shows a nonlinear and significant hysteresis characteristic due to nonlinear and viscoelastic property of the silicon rubber encapsulation. An average best-fit straight line sensitivity of 30.9 fFkPa−1 was recorded. The sensitivity of shear stress sensor is found to be 8.1 fFkPa−1. The three sensing elements also demonstrate a good cross-sensitivity performance of 3.1% on average. This paper proves that a common flexible printed circuit board (PCB) base material could be transformed into stretchable circuits with integrated multimodal sensor using established PCB fabrication technique, laser machining, and sheet metal forming method.

To study the effect of food flow rheology on the human esophageal swallowing process, a biologically inspired actuator prototype has been developed. The actuator is made of silicone rubber where smooth and continuous peristaltic motion is generated by inflating air chambers distributed within its body. The soft material gives the actuator intrinsic compliance and infinite degrees of freedom in motion. Thus, it is challenging to model the behavior online by current methods. In order to investigate the large-scale deformation of the soft-bodied actuator in response to the air chamber pressures, a geometrically simplified two-dimensional (2-D) model composed of separated beam-shaped elements is proposed. It considers the mechanical properties of the material, the sophisticated geometry of the actuator as it deforms, and the distributed pressure behavior. Empirical data from the actuator prototype (captured by articulography) and the simulated results are compared to investigate the accuracy of the model. The differences of deformations between the experimental results and the theoretical model are analyzed.

Purpose of review Investigation and surgical manipulation of the larynx, pharynx, and oesophagus suffer from inherent challenges with access to the sites of interest. To reduce trauma and external scarring, visualization and minimally invasive interventions by the transnasal or transoral routes have become more prevalent. This article discusses engineering methods used to understand and overcome the mechanical constraints inside the airway and upper gastrointestinal tract, and examines the role that robotics and engineering are beginning to play in modelling of surgical interventions in this region. Recent findings Although robotic solutions to minimally invasive surgery of the airway and upper gastrointestinal tract already exist, there is still scope for increasing the breadth of their use. Physical and virtual models of these organs are used to investigate the capability and limitations of manual and robotic surgical interventions in this region. Understanding the tissue mechanics and tool capabilities is central to improving outcomes in the clinical setting. Both physical and virtual modelling modalities are used in training surgeons for both manual-assisted and robot-assisted surgeries. Summary Minimally invasive surgical interventions via the transnasal and the transoral route are strong candidates for overcoming access issues to the airway. They are likely to become more robotically driven as the demand for higher dexterity and accuracy increases for fine manipulation. Physical and virtual organ models are required to enable surgical training for these procedures.

The design, development, and testing of a robot-assisted biopolymer thin shell free-form printing system is presented. This fused-deposition style printing system directly extrudes pellets of biomaterial and is capable of printing directly on organically shaped 3D curved surfaces. The screw extrusion method allows direct printing from pellets. The printed structure is supported by a pre-built base (a mandrel), which is manipulated by a six degree-of-freedom industrial robot arm, an ABB IRB120. This robot is used to manipulate the orientation of the support mandrel surface. The print method works by projecting a desired 2D image onto a mathematical model of the pre-built mandrel surface. This produces a 3D point path for the system to follow. These points are then converted into vectors for the robot’s pose and orientation of the end effector, which ensures that the extrusion remains normal to the mandrel surface. Inverse kinematics is applied to convert the trajectory into joint positions for the robot to follow. This paper demonstrates the utility of the developed system through simulation and printing of concave surface designs.

Soft robotics is an area where the robots are designed by using soft and compliant modules which provide them with infinite degrees of freedom. The intrinsic movements and deformation of such robots are complex, continuous and highly compliant because of which the current modelling techniques are unable to predict and capture their dynamics. This paper describes a machine learning based actuation and system identification technique to discover the governing dynamics of a soft bodied swallowing robot. A neural based generator designed by using Matsuoka’s oscillator has been implemented to actuate the robot so that it can deliver its maximum potential. The parameters of the oscillator were found by defining and optimising a quadratic objective function. By using optical motion tracking, time-series data was captured and stored. Further, the data were processed and utilised to model the dynamics of the robot by assuming that few significant non-linearities are governing it. It has also been shown that the method can generalise the surface deformation of the time-varying actuation of the robot.

In order to understand fluid transport throughout esophageal swallowing in man, a biologically inspired soft-robotic peristaltic actuator has been designed and manufactured to perform biomimetic swallowing. To achieve congruence with current mathematical modeling techniques for esophageal peristalsis, this paper examines the capability of the device (empirical) towards achieving sinusoidal transport waves with variations of clinically significant parameters such as amplitude and wavelength. The performance of the device to fit the commanded trajectory, by minimization of mean squared error, is tested over the range of wavefront length 30 $\le \lambda /2 \le$ 60 mm and amplitude 6–8 mm in a two-dimensional capability analysis. It is found that the device is capable of achieving propagation of families of wave shapes with less than 5% full scale mean error, which improves for increasing wavefront length and reducing amplitude. The aim for the device in the future is to inspire a novel rheometric technique in the physical domain which characterizes fluid formulations based on intrabolus pressure signatures. This analysis expresses the trajectory generation technique and performance of the novel device to produce continuous peristaltic waves towards biomimetic swallowing.

The relationships among bolus formulation, engineering rheometric quantities, and peristaltic transport effects are examined in this paper. Investigation of a series of synthetic bolus materials and swallowing strategies is conducted using a novel peristaltic swallowing robot inspired by esophageal swallowing, which manifests as a benchtop rheological instrument. To determine the validity of biomimetic swallowing, manometry, a clinical technique for capturing swallowing pressure profiles is used to establish congruence between the robotic findings and those of a clinical nature. To determine the contribution of the bolus and swallowing strategy to the intraluminal pressure signature (ILPS), three parameters were varied: peristaltic wave velocity (20, 30, 40 mm $\mathrm{s}^{-1}$ ), wavefront length (40, 50, and 60 mm) and starch thickener (Nutulis, Nutricia) concentration (25, 50, 75, 100, and 150 g $\mathrm{L}^{-1}$ ) were investigated. Wave velocity and starch-based bolus formulation concentration were found to exhibit the most profound changes in the intrabolus pressure signatures. The highest bolus tail pressure gradient of 0.33 kPa $\mathrm{mm}^{-1}$ was achieved with a 150 g $\mathrm{L}^{-1}$ bolus formulation being transported at 40 mm $\mathrm{s}^{-1}$ with a wavefront length of 60 mm. In each dimension, the relationship between the parameters and features of the manometric pressure signature are found to be nonlinear owing to the shear-thinning, non-Newtonian nature of the model bolus fluid. The robotic ILPSs are synonymous with those of a clinical nature, suggesting that the swallowing robot has merit as a novel, biologically inspired, bolus investigation tool external to the human body.

The task of autonomously gripping delicate objects such as fresh produce remains a challenge even in modern robotics. Current robotics grippers are mostly made of mechanical linkages and actuators which follow very structured trajectories. As these exhibit little mechanical compliance they can readily apply too much pressure as a point load, leading to blemishing or bruising of produce (eg. kiwifruit). In order to overcome this, this paper proposes a soft-robotic approach, which has the ability to morph and conform around the grasped object. This increases the contact area between the object and the gripper, resulting in a more equal distribution of force, and a lower effective contact pressure. Additionally, this allows for a more secure grip to be achieved. The proposed gripper design is inspired by the soft-touch of the human hand, which is presently the most suitable manipulator for fruit-picking tasks. The soft robotic device is manufactured from a composite of Ecoflex 00–30 Room Temperature Vulcanisation Rubber and polymer mesh. This paper describes the specification, design, manufacture and validation of the novel soft robotic gripper as it emerged from the conceptual phase into its application domain (kiwifruit gripping and manipulation). The physical results are crossexamined with those from FEA analysis.

3D Printing additive manufacturing is a rapidly developing form of technology. Currently able to manipulate many polymers (both synthetic and organic) this technique is quickly becoming an integral part of biotechnological developments. This paper highlights the fundamentals of this technology namely the mechanisms employed in standard 3D printing it then introduces tissue engineering a field in which current versions of this technology have been employed as bioprinting. The limitations with respect to tissue engineering are discussed outlining the current technologies inability to produce nanofibre based structures common in tissue such as tendon cartilage and cornea. From this requirement for nanofibre production electrospinning is introduced as a potential pathway for future tissue engineering 3D printing technologies and finally the current combination of this technology with 3D Printing is discussed yielding current limitations in retaining required nano-resolutions.

The nature of fibre placement/manipulation in electrospinning has been recorded through the utilization of surface actuation and electrostatic manipulation. This study investigates the potential of a simplistic approach to fibre placement manipulation through the utilization of non-uniform non-conducting collecting surfaces. A solution of Nylon 6,6 and Formic acid was electrospun with an ES1a device and through the use of SEM analysis submicron and nanofibre alignment was identified. This study achieved the generation of actuation-less and electrode-less alignment reiterating current literatures rationale of alignment formation. The study noted limitations regarding the potential combination of mold/cavity and electrospinning based manufacturing. From this work future recommendations regarding surface modification have been derived.

The specification and design of a novel peristaltic actuator is communicated. The actuation manifests as a continuous, distributed, and compliant peristaltic actuation. The occlusive nature of force distribution on the transport conduit results in materials being transported in front of a wave which has features of geometry and wave tail seal pressure. The behavior of these aspects profoundly affects the transport process. The device, of silicone rubber construction, has no internal skeletal structure and is pneumatically actuated which allows for continuous and compliant transport. The device is characterized by the synergy of geometrical and occlusive pressure measurements in response to actuation. This is performed for the “dry swallow” case (with no bolus) for single peak, single inflection waves. Techniques typical of medical investigation were exploited. Wave geometry was captured by articulography, complemented by wave seal pressure investigation by manometry. This paper describes the inspiration, specification, and experimental techniques used to develop and characterize the behavior of the biologically inspired, peristaltic, robotic device for assertion pressures up to 71.5 kPa. It is found that the device is capable of producing wave amplitudes and seal pressures of a similar magnitude (complete occlusion with >15-kPa seal) to the human esophagus which confirms achievement of the fundamental peristaltic parameters.

Provision of modified foods and drinks is one of the approaches for dysphagia management, which is based on the assumption that food with proper texture and rheological properties will allow dysphagia patients to swallow safely and maintain adequate nutrition. However, lack of information about the in vivo swallowing process and its interaction with food flow has obstructed the effective management of dysphagia. In the esophageal swallowing stage, masticated food is transported through the esophagus to the stomach by a peristaltic mechanism, which is generated by sequential contraction and relaxation of esophageal muscles. Inspired by this behavior, a soft actuator is proposed to provide a nonrisk environment aiming to facilitate investigations of the most effective properties of food for the management of the swallowing disorders. The wave-like motion is first specified according to the in vivo measurement of human esophageal peristalsis. Finite-element analysis simulations are carried out to aid the structure design before prototype manufacture. Constructed by casting silicon rubber in a three-dimensional (3-D) printed customized mold, the novel actuator has soft structure resembling its human counterpart, which has a flexible muscular structure. Multiple layers of inflatable chambers are embedded and distributed along the axis of a food passage regularly, which locates at the center of the actuator. The actuator is capable of generating a peristaltic wave and pushing a bolus along the passage. The closure of the tube and the velocity of the propagation wave are going to be adjusted to achieve the trajectories recorded experimentally, by regulating the compressed air pressure pumped into chambers actively.

Users of prosthetic hands, such as upper limb amputees, require tactile feedback and sensation to successfully achieve complex gripping and grasping tasks. Whilst there are many methods of electronically capturing this interaction (through electronic pressure sensor arrays) there are limited methods of interfacing this data with the human brain. So-matotopical approaches do exist, however these are typically very invasive, and rely on access to the nerve. As an alternative approach, this paper investigates sensory substitution, whereby the user's sense of sound is exploited as a feedback interface between the sensors and the brain. A study, consisting of 8 participants, and a randomized trial method, is used to determine the perceptual latency and range sensitivity across a series of modulation techniques including frequency, volume, and beating. Two of these were used simultaneously to determine if two degrees of freedom were able to be comprehended simultaneously. It is found that multi-channel audio feedback is suitable for low bandwidth feedback applications so long as it can deal with latency of at least 600 ms. The capability of this interface has been captured in terms of time delay, learning curve, task correlation, and accuracy.

Soft-robotic structures and their materials are typically chosen according to a biological example. Medical imaging has been used to obtain 3D models of biological structures to create moulds for production of artificial, soft robotic counterparts. However, it is not enough to simply copy the geometry of these organisms; robots must be able to be modeled, and controlled, such that they can perform meaningful tasks. This involves investigating the robot's capability after it has been manufactured. The similarities between the biological and artificial robotic materials allow us to use methods from medical imaging in soft robotics. This paper proposes the use of medical imaging and alternative medical investigation methods for the static and dynamic characterization of soft robots and involves two soft-robotic case studies: a peristaltic pump (swallowing robot), and a peristaltic table. Articulography and manometry are shown to be useful techniques for investigation of the peristaltic pumping robot, and visual 3D scanning is demonstrated for the peristaltic table. Alternative medical investigation methods such as magnetic resonance imaging, computed tomography, and ultrasound are considered as other possibilities that require further investigation.

The consumption of liquid and solid foods is primal to the maintenance of adequate hydration and nutrition in man. Ingestion is a complex process where palatable material is broken down and discretized into boluses after which they are conveyed to the stomach for digestion. There exists difficulty in monitoring the efficacy of bolus transport through the deglutitive apparatus in vivo, especially in patients which exhibit pathological difficulties. To understand the effects of bolus rheology on the deglutition process we propose to develop a bio-mimetic mechatronic swallowing device. This will facilitate investigation of the rheological properties as the bolus is in transit to determine how they interact with the swallowing process. These properties are of interest to food technologists who aim to develop foods for meeting consumer acceptance of various requirements, such as for dysphagic populations to facilitate safe swallowing. The purpose of this review is to develop an awareness of the physiological system and the transferability of the geometrical, actuation, and control concepts into the engineering domain, for the purpose of building a swallowing robot. It presents a body of knowledge, beginning with the behavior and measurement of the deglutitive apparatus, followed by an investigation of deglutitive adaptation in response to rheological stimuli. The neural control strategies are then discussed before concluding with the state of, and demand for, research in the medical, food textural, and swallowing robotic fields.

The field of soft robotics is continuing to expand into exploring the possibilities for novel, non-skeletal, transport and locomotion systems inspired by biological phenomena. Application of these techniques toward development of an anthropomorphic esophageal swallowing robot requires overcoming of many soft robotic design and characterization challenges. Additionally, soft-robots require vastly different methods of specification and validation than traditional robots, as they typically exhibit less well-defined degrees of freedom. This chapter reveals a series of novel methods to: establish interdisciplinary specifications for the esophageal swallowing process, develop a soft robotic analogue in the engineering domain, and demonstrate its capability.

The demand for novel actuation and sensation technologies has seen the emergence of the biomimetic engineering field where inspiration is drawn from phenomena observed in nature. Soft robotic techniques are particularly suitable for physical modeling in this area as they can be designed to manifest features such as mechanical compliance and continuity. The process of peristalsis is common in many organisms for locomotion or pumping transport of fluid or semi-solid materials. This research initiative looks into how inspiration from the esophageal phase of swallowing can be communicated into the engineering domain such that a physical model of the esophagus can be developed. The resulting device is of a soft-robotic nature, asserted by pneumatic actuation on a silicone rubber conduit. The continuous nature of device output, and its perturbation throughout pumping transport present some interesting trajectory generation and control challenges. The inspiration for the mechanical design as well as the embodiment of device transport intelligence is described.

Textured food is provided to dysphagia populations in clinical practice for assessment and management of swallowing disorders. A considerable amount of measurements showed that the textural properties of food can affect the performance of human swallow significantly. However, the selection of food for a specific subject is difficult, due to the complexity of the biological structures and the potential risks of in vivo testing. For the purpose of providing a safe environment for food flow study, a novel soft actuator capable of producing peristalsis movement was proposed. During the esophageal swallowing, which is the last stage of human swallow, food is transported through the muscular tube by peristalsis mechanism. The motion pattern is generated by the coordinated contractions of circular muscles of the esophagus. Inspired by human esophagus and the biological process, the actuator was designed to have a completely soft body without any hard components. Discrete chambers are embedded inside the body regularly and a cylindrical food passage locates at the center of the actuator. Finite element analysis (FEA) was used to determine the structure parameters of the actuator. The soft body was fabricated by casting silicon material in a custom mold. Preliminary experiments have been performed to characterize the actuator.

To investigate the impact of viscosity and peristaltic transport parameters on manometric pressure signatures, a reproducible swallowing process is required. Due to inter- and intra-subject variability from swallow to swallow, the human body does not represent an optimal mechanism for such an investigation. A smooth and continuous swallowing soft-robot has been developed to produce biomimetic swallowing trajectories, and is proposed to operate as a bench-top bolus rheometric investigation method. The method compares conventional viscometry and pressure signature findings from robotic swallowing experiments. The robotic aspect of experimentation involved 450 biomimetic swallows (10 repetitions of 45 unique experiments). The method examined swallowing transport in three dimensions: bolus formulation, peristaltic wavelength, and peristaltic velocity, each of which are known to contribute to safe and effective swallowing in vivo. It is found that the pressure gradients and magnitudes are commensurate with clinical reports on biological swallowing, on the order of 100 mmHg peak, however, the relationship between viscosity and pressure signatures is less clear. Bolus transport cannot be predicted as a function of bolus viscosity alone. Traditional viscometric data at 50 s−1, as used in clinical practice, may not be a strong indicator of swallow effort, safety, or efficacy in vivo.

Textural and rheological characteristics of foods are known to profoundly affect the swallowing process. Food technologists continue to exploit this notion in the management of symptomatic swallowing disorders (dysphagia) where novel foods are designed to elicit more reliable transport characteristics. Currently, little is understood about the relationship between food bolus formulation and its flow-induced interactions with the swallowing tract. Experimentation of a medical nature in this field is extremely challenging, and may put patients at risk. In the rheological domain the deformation fields are dissimilar to that of the biological system. In response to these limitations, quantitative assessment of bolus transport by a novel rheometric testing device is proposed. This paper describes the inspiration for a biologically-inspired robotic swallowing device to be applied to address these issues. This will allow for an improved understanding of swallowing mechanics and food design in the engineering, medical, and food technology fields.