Abstract
This paper presents a soft engine which performs up-and-down motion with four planar film-structured ionic polymer—metal composites (IPMC) actuators. This soft engine assembled with a stretchable Fresnel zone plate is capable of tuning the focus of ultrasonic beam. Instead of conventional clamps, we employ 3D printed frame pairs with magnets and a conductive gold cloth to provide an alternative solution for securing the IPMC actuators during assembly. The design and analysis of the zone plate are carefully performed. The zone plate allows the plane ultrasonic wave to be effectively focused. The motion of IPMC actuators stretch the metal-foil-made zone plate to tune the focal range of the ultrasonic beam. The zone plate, 3D frames and IPMC actuators were fabricated, assembled and tested. The stiffness normal to the stretchable zone plate with varied designs was investigated and the seven-zone design was selected for our experimental study. The force responsible for clamping the IPMC actuators, controlled by the magnetic attraction between the fabricated frames, was also examined. The driving voltage, current and resulting displacement of IPMC actuation were characterized. The developed soft engine stretching the zone plate to tune the focal point of the ultrasonic beam up to 10% was successfully demonstrated.
Highlights
Over the last decade, electroactive polymers (EAPs) have garnered significant attention because of the promising characteristics they exhibit in their application to soft actuators [1–4]
Its actuating performance is very limited without a dominantly high voltage. ionic polymer–metal composite (IPMC) materials possess exceptional advantages for usage in soft actuators because they can be manipulated with relatively low voltages and can produce large bending motions [5–8]
We examined the displacement of the IPMC actuator operated in the first cycle and last cycle and found that the displacement decrease was within 15% after this long-period operation
Summary
Electroactive polymers (EAPs) have garnered significant attention because of the promising characteristics they exhibit in their application to soft actuators [1–4]. Its actuating performance is very limited without a dominantly high voltage. Ionic polymer–metal composite (IPMC) materials possess exceptional advantages for usage in soft actuators because they can be manipulated with relatively low voltages (usually several volts) and can produce large bending motions [5–8]. A common IPMC actuator is made up of an ion-exchange thin membrane with metal particles plated on its top and bottom surfaces as electrodes which form a sandwich structure [9–11]. When a voltage drop is applied to the electrodes of an IPMC actuator, the cations along the water molecules travel towards the cathode and gather close to the electrode interface. The anions are secured within the clusters formed from the polymer network
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