A Retrofit Sensing Strategy for Soft Fluidic Robots

Soft robots are intrinsically capable of adapting to different environments by changing their shape in response to interaction forces with the environment. However, sensing and feedback are still required for higher level decisions and autonomy. Most sensing technologies developed for soft robots involve the integration of separate sensing elements in soft actuators, which presents a considerable challenge for both the fabrication and robustness of soft robots due to the interface between hard and soft components and the complexity of the assembly. To circumvent this, here we present a versatile sensing strategy that can be retrofitted to existing soft fluidic devices without the need for design changes. We achieve this by measuring the fluidic input that is required to activate a soft actuator and relating this input to its deformed state during interaction with the environment. We demonstrate the versatility of our sensing strategy by tactile sensing of the size, shape, surface roughness and stiffness of objects. Moreover, we demonstrate our approach by retrofitting it to a range of existing pneumatic soft actuators and grippers powered by positive and negative pressure. Finally, we show the robustness of our fluidic sensing strategy in closed-loop control of a soft gripper for practical applications such as sorting and fruit picking. Based on these results, we conclude that as long as the interaction of the actuator with the environment results in a shape change of the interval volume, soft fluidic actuators require no embedded sensors and design modifications to implement sensing. We believe that the relative simplicity, versatility, broad applicability and robustness of our sensing strategy will catalyze new functionalities in soft interactive devices and systems, thereby accelerating the use of soft robotics in real world applications

Modeling the behavior of elastic pouch motors

Pouch motors are one of the recently developed soft actuators, which are known particularly for their low-weight, ease of fabrication and large stroke. To date, several studies have been performed to develop and model new pouch motors designs to improve their functionality. All models assume that the material is behaving inextensibly, i.e. not stretchable. Here, we propose an analytical model for pouch motors where we consider the materials to be stretchable, and show that stretchability of pouch motors sets a limit for the maximum contraction and force, and therefore cannot be neglected even when using nearly inextensible materials. We evaluate our model qualitatively by conducting 'blocked-displacement' experiments on single pouches made of various materials with different elasticity

Volume compensation of large-deformation 3D-printed soft elastomeric elastocaloric regenerators

Elastomeric elastocaloric regenerators have great potential for use in low-stress elastocaloric cooling devices. However, these regenerators display an asymmetric fluid exchange when operating in an active elastocaloric cooling cycle, due to the large required strains and associated volume change. During strain, the fluid volume increases, which passively forces fluid flow into the regenerator; when the strain is released, the fluid volume decreases, which results in a fluid flow out of the regenerator. During a traditional elastocaloric cooling cycle, there are also active fluid flow periods provided by fluid displacers or pumps. Here, we study the passive fluid flow in high-strain regenerators using a numerical model and experiments in two types of regenerators. Hyperelastic models are used to fit the experimentally measured mechanical behavior of thermoplastic polyurethane elastocaloric elastomers, and the model is subsequently used to conduct finite-element simulations predicting regenerator volume changes for an applied strain of 200%–600%. We validated the results using a specifically designed setup for measuring volume changes using pressure differences on a parallel-plate regenerator. For a strain range of 200%–600%, the predicted volume change ratio is 69.5%, closely matching the experimental value of 66.7%. We observed that the middle region of the regenerator experiences a higher volume change, which can be accurately accounted by the numerical model

The ongoing quest for the first total artificial heart as destination therapy

Many patients with end-stage heart disease die because of the scarcity of donor hearts. A total artificial heart (TAH), an implantable machine that replaces the heart, has so far been successfully used in over 1,700 patients as a temporary life-saving technology for bridging to heart transplantation. However, after more than six decades of research on TAHs, a TAH that is suitable for destination therapy is not yet available. High complication rates, bulky devices, poor durability, poor biocompatibility and low patient quality of life are some of the major drawbacks of current TAH devices that must be addressed before TAHs can be used as a destination therapy. Quickly emerging innovations in battery technology, wireless energy transmission, biocompatible materials and soft robotics are providing a promising opportunity for TAH development and might help to solve the drawbacks of current TAHs. In this Review, we describe the milestones in the history of TAH research and reflect on lessons learned during TAH development. We summarize the differences in the working mechanisms of these devices, discuss the next generation of TAHs and highlight emerging technologies that will promote TAH development in the coming decade. Finally, we present current challenges and future perspectives for the field

A 3D-printed, functionally graded soft robot powered by combustion

Roboticists have begun to design biologically inspired robots with soft or partially soft bodies, which have the potential to be more robust and adaptable, and safer for human interaction, than traditional rigid robots. However, key challenges in the design and manufacture of soft robots include the complex fabrication processes and the interfacing of soft and rigid components. We used multimaterial three-dimensional (3D) printing to manufacture a combustion-powered robot whose body transitions from a rigid core to a soft exterior. This stiffness gradient, spanning three orders of magnitude in modulus, enables reliable interfacing between rigid driving components (controller, battery, etc.) and the primarily soft body, and also enhances performance. Powered by the combustion of butane and oxygen, this robot is able to perform untethered jumping.Chemistry and Chemical Biolog

Transition Year is what you make of it -- just be glad you have the chance

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