Biomimicry is a field of research that uses the functional and structural components of nature, at macroscopic and microscopic scales, to inspire solutions to problems in our industrial world. Soft robotics is an area of research that uses biomimicry, in this case, mimicking skeletal muscles (referred to in this field as “muscle-mimicking actuators”, to perform task of high difficulty, that can be operated in a harmlessly in different environments. One of the most recent advancements to develop from this field is the “Hydraulically amplified self-healing electrostatics (HASEL) actuator”. However, this method also brings many of the issues associated with the geometry of its design, especially with respect to the efficiency of the system. Though this system mimics the functionality of the skeletal muscle, there is room to adjust the existing electrostatic mechanisms, that distribute the locally produced force, to mimic the structure of the mechanism that distributes the force to the skeletal muscular, which is also locally produced. In this paper, we show that the current electrostatic parallel electrodes, as well as the zipping mechanisms, can be replaced with the sliding mechanism. This eliminates issues associated with compartmentalizing of the primary electrostatic force and the secondary hydraulic forces leading to a more efficient and controlled transmission electrostatic and hydrostatic forces to the load compared to current iterations and their geometric components.

The muscle-like movement and speed of the electrohydraulic actuator have granted it much attention in soft robotics. Our aim is to review the advancements in electrohydraulic actuators inspired by the Hydraulically Amplified Self-healing Electrostatic (HASEL) actuator. With this paper, we focus on the performance of 21 electrohydraulic actuator designs developed across five Universities, ranging from the earliest HASEL designs to the latest electrohydraulic designs. These actuators reported up to 60 N forces and contracting strains of up to 99%. The actuators with the best overall performance so far have been the Quadrant HASEL actuator and the HEXEL actuator, developed at the University of Colorado Boulder. However, notable is also the HALVE actuator (produced by ETH Zürich, Switzerland), which, by using a 5 µm PVDF-TrFE-CTFE film with a relative permittivity of 40, produced 100 times the electrostatic force of any of the electrohydraulic actuators under review. The latter shows that there is room for improvement as low force and displacement still limit the viability of the soft actuators in real-life applications.

HASEL (Hydraulically Amplified Self-Healing Electrostatic) actuators have gathered momentum in recent years; they are made of very-low-cost materials, making it easy for anyone to develop their own actuators, and they are “soft” and can achieve tasks that are very difficult to complete with traditional rigid actuators, e.g., grasping soft objects. Unfortunately, HASEL actuators are driven by high-voltage (HV) power supplies, which are expensive to control accurately and difficult to scale up for multichannel applications, e.g., prostheses. This paper presents a low-cost HV power supply designed for HASEL applications that generates 2–10 kV DC at 5% of the cost of the existing HV power supplies used in HASEL actuators. At the core of our design, there is a new control strategy based on controlling the charging and discharging of the actuator from the supply’s low-voltage (LV) side rather than switching the HV side with expensive HV optocouplers. Discharge is achieved via a secondary transformer and multiplier circuit, generating a negative HV output capable of discharging the HASEL effectively and safely up to 10 kV.

The muscle-like movement and speed of the electrohydraulic actuator have granted it much at-tention in soft robotics. Our aim is to review the advancements in electrohydraulic actuators in-spired by the Hydraulically Amplified Self-healing Electrostatic (HASEL) actuator. With this paper we focus on the performance of 21 electrohydraulic actuator designs developed across five Uni-versities, ranging from the earliest HASEL designs to the latest electrohydraulic designs. These actuators reported up to 60 N forces and contracting strains of up to 99%. The actuator with the best overall performance so far, has been the HEXEL actuator, developed at the University of Colorado Boulder. However, notable is also the HALVE actuator (produced by ETH Zürich, Switzerland), that by using a 5µm PVDF-TrFE-CTFE film with a relative permittivity 40, produced 100 times the electrostatic force of any of the electrohydraulic actuators under review. The latter shows that there is room for improvements as low force and displacement still limit the viability of the soft actuators in real-life applications.

Hydraulically Amplified Self-Healing Electrostatic (HASEL) actuators promise a future of adaptive robotics in a world where robotics is becoming increasingly integrated into our daily lives. Adaptive robotics needs to control multiple outputs with precision and speed. Unfortunately, expensive High Voltage control restricts the development of the HASEL actuator for commercial applications. This paper demonstrates a low-cost multi-channel High Voltage Power Supply (HVPS). The HVPS takes a 6 V input and controls multiple HASEL actuators from 0 to 10 kV, with a slew rate of up to 117.7 kV/s. In addition to controlling multiple channels, the low-cost HVPS can control two outputs with a single control module in an alternating pattern, similar to the way muscles control movement in alternating sequences—e.g., biceps and triceps. Previous work has shown that this low-cost HVPS is 95% cheaper than other power supplies used in the field of HASEL actuators. This work builds on the work reducing the cost of the HVPS by an additional 40%. This low-cost HVPS also reduces the amount of input required for control from four PWMs to one PWM with enable pins, drastically improving the performance of the device for multi-channel operation.

Utilising the open-source design of the Federica Prosthetic Hand, we introduce a redesigned print-in-place version that minimises assembly requirements without sacrificing functionality. The original Federica hand has a complicated, time-consuming assembly process. The print-in-place design removes the process of assembling the hand, making it easier for new users to use the design. The approach results in a 21% reduction in the bill of materials and a 21% reduction in weight. Though the 8 N force of the original Federica hand was not reached in this trial, the measured results show that under the same test conditions, the print-in-place hand can match the performance of the original. In a single-specimen analysis, the print-in-place hand produced a higher peak force in four of eight orientations. The redesigned prosthetic hand includes functional joints fully integrated into its structured design with a locking mechanism, eliminating the need for several metal bolts, and a revised dorsal finger contour, reducing the requirement for additional support structures during printing. As with the original hand, the print-in-place prosthetic is open source for anyone to access.