Resea R ch h ighlights Nature Reviews Materials | https://doi.org/10.1038/s41578-018-0010-2 | Published online 26 April 2018 SOFT ROBOTIC S Soft robots enable applications that and the angle between the wall and pressure supply into periodic interface with humans, for example, as the membrane at its edge. “The pressure oscillations, which is exoskeletons or in surgery. However, pressures at which the instability demonstrated in an earthworm- Combining soft pneumatic devices are typically occurs can be designed to match the like walker powered by a constant the bistable not completely soft because they pressure limits between which a soft pressure source. valve with are controlled by hard valves. Now, actuator operates,” explains Philipp The valve design still needs soft control George Whitesides and collaborators, Rothemund, an author of the article. tweaking before it can be used writing in Science Robotics, report on “The valve can therefore be designed in technologies. “In the current elements … a soft mechanical switch to control to autonomously perform the design, the valve consists of over will allow the airflow in soft actuators. control function. We demonstrated ten separate parts and requires execution of The soft valve consists of a this by incorporating the soft valve a similar number of fabrication hemispherical membrane separating into a soft robotic gripper, which was steps. For the valve to be adopted more complex two chambers. Its orientation — able to grasp an object once it came in technological applications, we functions upward or downward — depends on into contact with the gripper, much envision an integrated design that the pressure difference between the like if you were to catch a ball with requires fewer fabrication steps,” chambers. The membrane position your eyes closed, using only your says Daniel Preston, another author controls airflow through tubes sense of touch.” of the article. “Additionally, we have that run through each chamber: in Because the switching is tested the durability of the valve one chamber the tube is closed by hysteretic, that is, the membrane only at the lab scale, over 100,000 the membrane pushing on it and only inverts orientation when the actuation cycles. Even though we in the other chamber the tube is pressure difference crosses the did not observe any substantial left open and air flows. The valve up- to-down or the down-t o-up changes in performance, longer requires power only for switching, threshold, the valve is also insensitive durability tests would need to be which occurs when the pressure to fluctuations in pressure and can performed to demonstrate that the difference reaches a threshold, be used as a noise filter, analogous valve satisfies the requirements of causing the membrane orientation to noise filters used in digital signal commercial applications.” to become unstable and invert. The processing. The design of the valve There are also possibilities to thresholds of pressure difference can also be modified to make an expand the functionality of the depend on membrane thickness oscillator that converts a constant valves. “Combining the bistable valve with soft control elements, which were developed for microfluidic circuits, or combining multiple bistable valves will allow the execution of more complex functions. There are many different types of instabilities that occur in soft structures, which may be used in the future for the control of soft actuators,” concludes Preston. Zoe Budrikis, Associate Editor, Nature Reviews Physics ORIgInal aRTICle Rothemund, P. et al. A soft, bistable valve for autonomous control of soft actuators. Science Robotics 3, eaar7986 (2018) 72 | june 2018 | volume 3 w w w.nature.com/natrevmats © 2018 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. Daniel Preston
Nature Reviews Materials – Springer Journals
Published: Apr 26, 2018
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