soft material actuation through ultrasonic atomization

Department: Structural Engineering
Faculty Advisor(s): Kenneth J. Loh

Primary Student
Name: Hanjoo Lee
Phone: 858-353-3102
Grad Year: 2021

Student Collaborators
Morgan Funderburk,

Mechanical systems require actuation which involve transduction of one form of energy to mechanical work. Traditionally, these systems consisted of hard and rigid components since they enable rapid movement with high precision. However, recent development in technology require actuation systems to manipulate objects with various shapes and operate in unpredictable environments. Furthermore, hard components are not suitable for human interaction due to potential injuries such as collision or jamming. Soft robotics, on the other hand, have the potential to solve these challenges with their ductile and compliant properties. The soft nature of the material provides impact force attenuation along with conformability to effectively grasp objects or traverse through uneven terrain. Up to date, several different techniques have been developed to actuate these soft structures. Among those methods, applying pressure change demonstrated promising results through high power to weight ratio and fast actuation rate. Nonetheless, current setups involve separate large pumps and tethered tubes which limit their flexibility. The goal of this research is to introduce a new actuation method that involve pressure change through ultrasonic atomization. When a layer of liquid is subjected to ultrasonic waves that vibrate perpendicular to the surface, capillary waves are formed on the liquid-air interface. The amplitude of the capillary wave increases with increasing the ultrasonic wave and a critical point is reached when the liquid surface become unstable and eject small droplets. These small droplets enable higher evaporation rates compared to its bulk form, even under temperatures below boiling point. In this study, ethanol was enclosed inside a soft foldable structure which was atomized through a small external piezoelectric transducer. The evaporation of ethanol results in unidirectional expansion of the foldable structure. The experiments demonstrate a novel method of actuation which does not require complicated connections or an external pump.

Industry Application Area(s)

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