An Easy‐to‐Implement Toolkit to Create Versatile and High‐Performance HASEL Actuators for Untethered Soft Robots

Abstract

For soft robots to have ubiquitous adoption in practical applications they require soft actuators that provide well‐rounded actuation performance that parallels natural muscle while being inexpensive and easily fabricated. This manuscript introduces a toolkit to rapidly prototype, manufacture, test, and power various designs of hydraulically amplified self‐healing electrostatic (HASEL) actuators with muscle‐like performance that achieve all three basic modes of actuation (expansion, contraction, and rotation). This toolkit utilizes easy‐to‐implement methods, inexpensive fabrication tools, commodity materials, and off‐the‐shelf high‐voltage electronics thereby enabling a wide audience to explore HASEL technology. Remarkably, the actuators created from this easy‐to‐implement toolkit achieve linear strains exceeding 100%, a specific power greater than 150 W kg −1 , and ≈20% strain at frequencies above 100 Hz. This combination of large strain, extreme speed, and high specific power yields soft actuators that jump without power‐amplifying mechanisms. Additionally, an efficient fabrication technique is introduced for modular designs of HASEL actuators, which is used to develop soft robotic devices driven by portable electronics. Inspired by the versatility of elephant trunks, the above capabilities are combined to create an untethered continuum robot for grasping and manipulating delicate objects, highlighting the wide potential of the introduced methods for soft robots with increasing sophistication.

Liquid Metal–Based Soft Microfluidics

“…Soft robots, distinguished from the conventional robotics, not only show the robotic features for complete targeted tasks, but also offer intrinsic adaptability and reconfigurability to their surroundings for easier actuation and function . LM, either in the form of droplet or in the form of doping materials, can serve as the key component for the actuation of the soft‐robotic machines via energy conversion processes that transform various kinds of energy, such as magnetic energy, electric energy, thermal energy, light energy and chemical energy to the kinetic energy .…”

High‐Strain Peano‐HASEL Actuators

“…The load–strain curves of four‐unit actuators based on rectangular and notched electrodes show that notched electrodes are advantageous compared to rectangular electrodes in the low‐load region (Figure d). The screen‐printed carbon electrodes are easier to fabricate and help the actuators achieve larger strains because they reduce the bending stiffness of the shell–electrode bilayer compared to hydrogel electrodes with inextensible BOPP backing. Thus, the screen‐printed electrodes facilitate buckling in the transition zones between the zipping and contracting regions.…”

“…Recently developed hydraulically amplified self‐healing electrostatic (HASEL) actuators combine the speed and self‐sensing ability of DEAs and the versatility of PAMs while avoiding important drawbacks by utilizing an electrohydraulic principle to locally displace a hydraulic fluid and by being able to self‐heal from electric damage . Additionally, their combination of speed, efficiency, and versatility makes them promising candidates for use in untethered systems …”

Dynamics of electrohydraulic soft actuators

“…We believe that many types of electrohydraulic soft actuators exhibit an inertial and a viscous dynamic regime. Several types of electrohydraulic actuators exist whose shells consist of thin, inextensible films (12,35,36). For these actuators, the presented scaling analysis may readily be modified to identify the governing timescales to account for differences in geometry (12,35) and modes of electrohydraulic zipping (35,36).…”