27 March 2018 Actuation of soft materials through ultrasonic atomization
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Abstract
Soft robotics have the potential to improve traditional robotics since soft materials are safer and more compliant to unpredictable surroundings. To date, various methods have been investigated to actuate such soft materials. The main objective of this research is to introduce a new method of soft robotic actuation through ultrasonic atomization. The mechanism of actuation is based on purposefully embedding pockets of liquid in a soft polymer matrix. It is known that, when a layer of liquid is subjected to ultrasonic waves, a capillary wave forms on the surface. When the amplitude of the ultrasonic wave exceeds a critical point, small droplets are ejected from crests of the capillary wave. The small droplets allow the liquid to evaporate at faster rates even when the temperature is below the boiling point, thereby building up vapor pressure and expanding the soft polymer matrix. Here, a soft structure was fabricated that enclosed a small amount of ethanol. Ultrasonic waves generated by a piezoelectric transducer atomized and evaporated ethanol in the expandable structure. During the expansion, temperature, displacement, and stress was measured to characterize the resulting actuation behavior of the system. Separate sets of tests were conducted on a hot plate to compare the effect of atomization versus evaporation. In addition, the voltage of the piezoelectric transducer was controlled to analyze the relationship between voltage and actuation rate. Finally, the durability of the expandable structure was also shown through cyclic actuation and cooling. The results showed the potential of ultrasonic atomization as a new mechanism for soft robotic actuation, where actuation could be produced and controlled in a noncontact manner (i.e., without requiring a tethered connection to deliver air or fluid).
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Han-Joo Lee, Han-Joo Lee, Morgan Funderburk, Morgan Funderburk, Kenneth J. Loh, Kenneth J. Loh, } "Actuation of soft materials through ultrasonic atomization ", Proc. SPIE 10593, Bioinspiration, Biomimetics, and Bioreplication VIII, 105930Z (27 March 2018); doi: 10.1117/12.2296627; https://doi.org/10.1117/12.2296627
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