Designing information-rich and space-efficient sensors is a key challenge for soft robotics, and crucial for the development of safe soft robots. Sensing and understanding the environmental interactions with a minimal footprint is especially important in the medical context, where portability and unhindered patient/user movement is a priority, to move towards personalized and decentralized healthcare solutions. In this work, a pulsating fluidic soft sensor (PFS) capable of determining location, pressure and contact area of press events is shown. The sensor relies on spatio-temporal resistance changes driven by a pulsating conductive fluid. The sensor demonstrates good repeatability and distinction of single and multiple press events, detecting single indents of sizes greater than 1 cm, forces larger than 2 N, and various locations across the sensor, as well as multiple indents spaced 2 cm apart. Furthermore, the sensor is demonstrated in two applications to detect foot placement and grip location. Overall, the sensor represents an improvement towards minimizing electronic hardware, and cost of the sensing solution, without sacrificing the richness of the sensing information in the field of soft fluidic sensors.

Soft robots have shown remarkable distinct capabilities due to their high deformation. Recently increasing attention has been dedicated to developing fully soft robots to exploit their full potential, with a recognition that electronic powering may limit this achievement. Alternative powering sources compatible with soft robots have been identified such as combustion and chemical reactions. A further milestone to such systems would be to increase the controllability and responsiveness of their underlying reactions in order to achieve more complex behaviors for soft robots. In this paper, we present a thermally-activated reactor incorporating a biocompatible hydrogel valve that enables control of the biochemical reaction of sugar and yeast. The biochemical reaction is utilized to generate contained pressure, which in turn powers a fluidic soft actuator. Experiments were conducted to evaluate the response time of the hydrogel valves with three different crosslinker concentrations. Among the tested concentrations, we found that the lowest crosslinker concentration yielded the fastest response time of the valve at an ambient temperature of 50°C. We also evaluated the pressure generation capacity of the reactor, which can reach up to 0.22 bar, and demonstrated the thermoresponsive behavior of the reactor to trigger a biochemical reaction for powering a fluidic soft actuator. This work opens up the possibility to power and control tetherless and fully soft robots.

In biomedical engineering, robotic implants provide new methods to restore and improve bodily function, and regenerate tissue. A significant challenge with the design of these devices is to safely actuate them for weeks or months, while they are residing in a patient's body. Magnetic, and other force-at-distance actuation methods, allow mechanisms to be controlled remotely and without contact or line of sight to the device. In this paper, we present a novel magnetic field driven wireless motor. The motor drives a robotic implant for the treatment of long gap esophageal atresia and short bowel syndrome. The motor is equipped with two oppositely oriented permanent magnets which experience forces in opposite directions when a magnetic field is applied tangential to the magnets' directions. The implant can produce a force of 2 N. It is demonstrated with an ex vivo porcine esophagus.

Achieving compact and biocompatible actuators with sensing capabilities is a key challenge for the safety critical and highly patient-specific biomedical field. In this study, a compact and versatile soft fluidic sensor-actuator capable of measuring both force and displacement in static and dynamic conditions is presented. Pressure and resistance are shown to be interchangeable in predicting load and sensor-actuator height, and showed good repeatability and distinction between the loaded and constrained conditions tested. Furthermore the sensor-actuator is demonstrated in a probe application and showed comparable findings to a tensile test machine when tested on three objects of varying stiffness. Overall, this sensor-actuator has the potential to be a key building block for biomedical robots that require large expansion, as well as continuous monitoring of both displacement and force.

Inspired by the traditional art of paper folding, origami, autonomous production of 3D structures from 2D sheets can be achieved by the implementation of self-folding techniques. One technique to achieve such transformation is the usage of thermo-responsive smart materials such as self-folding polymeric films, which can be controlled by heat to shrink. Achieving remote self-folding with a practical approach remains a major challenge due to the requirement for specific environments, or having to accompany electronics on origami, which limits the complexity of the origami design. In this paper, we present a wireless method to trigger the thermo-responsive self-folding process of the origami robots through magnetic induction. The proposed method is applicable for all electrically conductive materials and can wirelessly fold a mobile origami robot with a size of 32 × 30 mm2. This method eliminates the need for inclusion of electronics on the origami or usage of complicated trigger methods and environmental conditions, allowing the robot to fold in a wider range of applications such as in constrained spaces.

Soft robots are known for their ability to comply and having superior extensibility. However, one of the limitations of most of these robots is that they can stand only a limited amount of load before buckling, and they feature a non-negligible initial height. Hybrid soft-rigid actuators seem to offer a trade-off between compliance and the amount of load they can withstand, but only a few simple models have been proposed to describe the behavior of these actuators. In this paper, we propose a design, model and experimental validation of a soft actuator based on stackable Hyperelastic Ballooning Membranes (HBMA). This actuator shows an extensibility higher than 179%, as well as an ability to stand more than 20 times its own weight at a pressure as low as 35 kPa. Two models, giving the dynamic behavior of the HBMA in terms of displacement and pressure, have been derived from different hyperelastic models (Neo-Hookean and Mooney-Rivlin) and compared in terms of accuracy and robustness. Finally, an example of a hybrid soft-rigid continuum ballooning robot built with HBMAs is presented and characterized experimentally.

In this study, a novel robotic bioreactor is presented with capabilities of closed-loop control of force and displacement applied to a tissue scaffold and tissue scaffold stiffness calculation. These characteristics bring the potential of a robotic bioreactor that can optimize the mechanical properties of tissue constructs in order for them to match those of native tissues. Custom position and force control signals are designed to maintain a steady tensioning of the tissue scaffold while the latter one’s mechanical properties evolve in time. We propose a simple model to support the hypothesis that the stiffness of a cell-seeded scaffold increases over time, and thus force control signals need to be adjusted accordingly. The robotic bioreactor is able to measure the stiffness of a scaffold sample relatively accurately, with an average standard deviation of 0.2N/mm. The combination of accurate stiffness measurements and a closed-loop control system equips the robotic bioreactor with the fundamental requirements to achieve stiffness based force control in future in vitro experiments, and thus to a tissue-scaffold responsive technology for advanced tissue engineering.

It is known that the interior of the human body is one of the most adverse environments for a foreign body, such as an in-vivo robot, and vice-versa. As robots operating in-vivo are increasingly recognized for their capabilities and potential for improved therapies, it is important to ensure their safety, especially for long term treatments when little supervision can be provided. We introduce an implantable robot that is flexible, extendable and symmetric, thus changing shape and size. This design allows the implementation of an effective fault tolerant control, with features such as physical polling for fault diagnosis, retraction and redundancy-based control switching at fault. We demonstrate the fault-tolerant capabilities for an implantable robot that elongates tubular tissues by applying tension to the tissue. In benchtop tests, we show a reduction of the fault risks by at least 83%. The study provides a valuable methodology to enhance safety and efficacy of implantable and surgical robots, and thus to accelerate their adoption.

Soft robotics has advanced the field of biomedical engineering by creating safer technologies for interfacing with the human body. One of the challenges in this field is the realization of modular soft basic constituents and accessible assembly methods to increase the versatility of soft robots. We present a soft pneumatic actuator composed of two elastomeric strands that provide interdependent axial and radial expansion due to the modularity of the components and their helical arrangement. The actuator reaches 35% of elongation with respect to its initial height and both chambers achieve forces of 1N at about 19kPa. We describe the design, fabrication, modeling and benchtop testing of the soft actuator towards realizing 3D functional structures with potential medical applications. An example of application for soft medical robots is tissue regenerative for the long-gap esophageal atresia condition.

Gastric ulcer is a chronic and complex (and often complete) erosion of the stomach wall that happens as a complication of a previous chronic, inflammatory process. It represents a catastrophic situation in which the patient is critical and its conditions need to be treated fast. This study presents a remotely navigatable and deployable ingestible patch and plug for gastric ulcer treatment. The patch/plug structure is made of agarose hydrogel that can change rigidity through hydration and dehydration. When dehydrated, it is rigid and can maintain a folded configuration so it can be ingested as a “pill”. This can be guided to the targeted location by a magnetic field, and be deployed instantly by hydration, namely by supplying water from the mouth. Due to the deployable origami design, it exhibits an expansion of 10 times its initial surface area, making the device suitable for the use of dressing a surface as a patch, and filling a hole as a plug.

Developing miniature robots that can carry out versatile clinical procedures inside the body under the remote instructions of medical professionals has been a long time challenge. In this paper, we present origami-based robots that can be ingested into the stomach, locomote to a desired location, patch a wound, remove a foreign body, deliver drugs, and biodegrade. We designed and fabricated composite material sheets for a biocompatible and biodegradable robot that can be encapsulated in ice for delivery through the esophagus, embed a drug layer that is passively released to a wounded area, and be remotely controlled to carry out underwater maneuvers specific to the tasks using magnetic fields. The performances of the robots are demonstrated in a simulated physical environment consisting of an esophagus and stomach with properties similar to the biological organs.

This paper introduces robotic implants as a novel class of medical robots in the context of treating esophageal atresia. The robotic implant is designed to apply traction forces to the two disconnected esophageal segments to induce sufficient growth so that the two ends can be joined together to form a functioning esophagus. In contrast to the current manual method of externally applying traction forces, the implant offers the potential to avoid prolonged patient sedation and to substantially reduce the number of X-rays required. A prototype design is presented along with evaluation experiments that demonstrate its capabilities to apply traction forces to ex vivo esophageal tissues.

We introduce a soft-matter sensor that measures elastic pressure and shear deformation. The sensor is composed of a sheet of elastomer that is embedded with fluidic parallel-plate capacitors. When the elastomer is pressed or sheared, the electrodes of the embedded capacitors come closer together or slide past each other, respectively, leading to a change in capacitance. The magnitude and direction of the shear deformation is established by comparing the change in capacitance of multiple embedded capacitors. We characterize the soft sensor theoretically and experimentally. Experiments indicate that 2D shear and pressure deformation can be discriminated with approximately 500 μm and 5 kPa sensitivity, respectively. The theoretical predictions and experimental results are in reasonable agreement. We also propose improvements to the fabrication method in order to facilitate integration of soft-matter sensing with wearable electronics.

Stable grasp is the result of sensorimotor regulation of forces, ensuring sufficient grip force and the integrity of the held object. Grasping with a prosthesis introduces the challenge of finding the appropriate forces given the engineered sensorimotor prosthetic interface. Excessive force leads to unnecessary energy use and possible damage to the object. In contrast, low grip forces lead to slippage. In order for a prosthetic hand to achieve a stable grasp, the haptic information provided to the prosthesis wearer needs to display these two antagonistic grasp metrics (force and slip) in a quantified way. We present the design and evaluation of a wearable single-actuator haptic device that relays multi-modal haptic information, such as grip force and slip speed. Two belts that are activated in a mutually exclusive manner by the rotation direction of a single motor exert normal force and tangential motion on the skin surface, respectively. The wearable haptic device is able to display normal forces as a tap frequency in the range of approximately 1.5–5.0 Hz and slip speed in the range of 50–200 mm/s. Within these values, users are able to identify at least four stimulation levels for each feedback modality, with short-term training.

In this paper, we investigate possible means of communication between plants and machines. Plants are capable of sensing a variety of environmental information. In particular, Avocado trees have an apparent response to increasing drought levels. We read out two different communication channels: morphological changes (leaf inclination) and the electric potential of the stem (biopotential) using distance sensors and biopotential electrodes, respectively. Leaf inclination reliably triggers irrigation, whereas the changes of the biopotential indicate water uptake and can be used to automatically stop the irrigation. Hence, through systematic experiments we demonstrate that morphological changes and biopotentials provide suitable control signals for interfacing plants with machines, and open a possibility to exploit abilities of plants in robotic systems.

The human hand is one of the most complex structures in the body, being involved in dexterous manipulation and fine sensing. Traditional engineering approaches have mostly attempted to match such complexity in robotics without sufficiently stressing on the underlying mechanisms that its morphology encodes. In this work, we propose an artificial skin able to encode, through its morphology, the tactile sense of a robotic hand, characteristic to slippage events. The underlying layout consists of ridges and allows slippage detection and the quantification of slippage speed. Such encoding of slippage signal becomes suitable for relaying tactile feedback to users in prosthetic applications. This approach emphasizes the importance of exploiting morphology and mechanics in structures for the design of prosthetic interfaces.