Bio-Inspired Soft Proboscis Actuator Driven by Dielectric Elastomer Fluid Transducers

Abstract

In recent years, dielectric elastomer actuators (DEAs) have attracted lots of attention for providing multiple degree-of-freedom motions, such as axial extensions, torsion, bending, and their combinations. The wide applications include soft robots, artificial muscles, and biomimetic animals. In general, DEAs are composed of stretchable elastomers sandwiched by two compliant electrodes and actuated by applying external electric stimuli. Since most DEAs are limited by the breakdown thresholds and low strain-to-volume ratios, dielectric fluid transducers (DFTs) have been developed by substituting dielectric elastomers with dielectric fluids for high breakdown threshold voltages. In addition, DFTs have large rate of lateral extensions, due to their fluid contents, and are beneficial for soft actuators and pumping applications. In this research, we exploited DFTs to develop a soft spiral proboscis actuator inspired by the proboscises of butterflies for achieving uncoiling and coiling motions under external voltages. The bio-inspired spiral proboscis actuator (BSPA) was composed of a coil-shaped tube, a DFT-based pouch, and a spiral spring for mimicking the tubular part, a mechanism to uncoil the tube, and a mechanism to coil the tube, respectively. When applying external voltages to the pouch, the high dielectric fluid was injected into the empty coiled tube for uncoiling where the tube elongated from a compact volume to a stiff and flexible shape. When removing the exciting voltages, the tube retracted to its original coiled shape via the elastic spring. A prototype was designed, fabricated, and examined with high stimulating voltages. It was demonstrated that the proboscis actuator could achieve uncoiling and coiling motions consistently for several cycles. Compared to convection DEA-based pumps with fixed shapes, the proposed actuator is soft and beneficial for portable applications and coiling/uncoiling motions.

HASEL Artificial Muscles for a New Generation of Lifelike Robots—Recent Progress and Future Opportunities

“…org/licenses/by/4.0). [95] Copyright 2019, The Authors, published by MDPI. chamber, which acts as a reservoir of liquid dielectric, connected to a corrugated structure of smaller chambers (Figure 8a).…”

“…For example, we designed an actuator in which the corrugated structure was a Fibonacci spiral (Figure 8d); when activated, this actuator simultaneously curled and twisted. Lin et al [95] developed an actuator with an inverse curling motion, wherein a coiled spring was used as the strain limiting layer. When activated, the pressurized fluid within the shell caused the spring to uncoil, mimicking the deformation of a proboscis found in butterflies (Figure 8e).…”

Materials with Electroprogrammable Stiffness

“…These include a soft gripper driven by electrohydraulic pouch units that can grasp delicate objects, [ 117 ] an active electrohydraulic actuation plate with asymmetric electrodes to control the position of surface objects, [ 118 ] and a proboscis‐inspired electrohydraulic transducer that can stiffen or soften to produce coiling motions. [ 119 ] Leroy and Shea recently introduced hydraulically amplified taxels (HAXELs), which are millimeter‐scale HASEL actuators for virtual reality and augmented reality systems. Each HAXEL can achieve strains up to 500 microns and forces up to 300 mN, and can be tightly packed into flexible, cutaneous haptic feedback arrays that can be worn by a user.…”

From Bioinspired to Bioinformed: Benefits of Greater Engagement From Biologists

“…These terms are sometimes used synonymously and other times as similar but separate approaches, and their broadly ambiguous use has resulted in many cases where the bioinspiration or knowledge transfer is trivial. For example, the behaviour of an animal (e.g., the flapping of wings or proboscis extension in butterflies) can be replicated using soft robotics without reference to the underlying biological mechanisms (Lin and Liu, 2019;Yu et al, 2021).…”