Publications

Hydraulically-amplified, self-healing, electrostatic transducers that harness electrostatic and hydraulic forces to achieve various actuation modes. Electrostatic forces between electrode pairs of the transducers generated upon application of a voltage to the electrode pairs draws the electrodes in each pair towards each other to displace a liquid dielectric contained within an enclosed internal cavity of the transducers to drive actuation in various manners. The electrodes and the liquid dielectric form a self-healing capacitor whereby the liquid dielectric automatically fills breaches in the liquid dielectric resulting from dielectric breakdown. Due to the resting shape of the cavity, a zipping-mechanism allows for selectively actuating the electrodes to a desired extent by controlling the voltage supplied.

A pumping system includes a conduit with an inlet region and an outlet region and a first pump coupled with the conduit between the inlet region and the outlet region. The first pump includes a first actuator chamber configured to house at least a first actuator, a first pump chamber aligned along a longitudinal axis of the conduit, wherein the first pump chamber is in fluid communication with the inlet region and the outlet region, and a first flexible diaphragm separating the first actuator chamber from the first pump chamber. Methods for operating the pumping system are also disclosed.

An electro-hydraulic actuator includes a deformable shell defining an enclosed internal cavity and containing a liquid dielectric, first and second electrodes on first and second sides, respectively, of the enclosed internal cavity. An electrostatic force between the first and second electrodes upon application of a voltage to one of the electrodes draws the electrodes towards each other to displace the liquid dielectric within the enclosed internal cavity. The shell includes active and inactive areas such that the electrostatic forces between the first and second electrodes displaces the liquid dielectric within the enclosed internal cavity from the active area of the shell to the inactive area of the shell. The first and second electrodes, the deformable shell, and the liquid dielectric cooperate to form a self-healing capacitor, and the liquid dielectric is configured for automatically filling breaches in the liquid dielectric resulting from dielectric breakdown.

As soft electrostatic actuators find applications in bio-inspired robotics, compact and lightweight high voltage electronics that independently address many actuators are required. Here, a pocket-sized, battery-powered, 10-channel high voltage power supply (HVPS) is presented, which independently addresses each channel up to 10 kV. The HVPS uses one HV amplifier to create a HV rail and each output connects to the rail via custom optocouplers that are pulse-width modulated to vary their conductance. These optocouplers distribute charges to and from electrostatic devices at each output, creating a charge-controlled driving scheme that can generate independent and nearly arbitrary actuation waveforms for each channel. The HVPS weighs 250 g and measures 8.4 cm × 13.3 cm × 2 cm, about the size of a smartphone. The HVPS is characterized when driving hydraulically amplified self-healing electrostatic (HASEL) actuators. While powering a 5 nF actuator, the output of the HVPS reaches 8 kV in 100 ms and drives a 1.5 nF actuator at 100 Hz (0 to 5.4 kV). The HVPS powers an active surface consisting of an array of HASELs and generates undulatory locomotion of a soft robotic inchworm, highlighting the potential for compact HV electronics that power multi-degree-of-freedom robotic systems based on electrostatic devices.

A hydraulically amplified self-healing electrostatic (HASEL) transducer includes a composite, multi-layered structure. In an example, a HASEL transducer includes a dielectric layer including at least one fluid dielectric layer. The dielectric layer includes a first side and a second side opposing the first side. The HASEL transducer further includes a first electrode disposed at the first side of the dielectric layer, a second electrode disposed at the second side of the dielectric layer, a first outer layer disposed at the first electrode opposite the dielectric layer, and a second outer layer disposed at the second electrode opposite the dielectric layer. The first outer layer and second outer layer exhibit different mechanical and electrical properties from the dielectric layer.

Locomotion through rolling is attractive compared to other forms of locomotion thanks to uniform designs, high degree of mobility, dynamic stability, and self-recovery from collision. Despite previous efforts to design rolling soft systems, pneumatic and other soft actuators are often limited in terms of high-speed dynamics, system integration, and/or functionalities. Furthermore, mathematical description of the rolling dynamics for this type of robot and how the models can be used for speed control are often not mentioned. This article introduces a cylindrical-shaped shell-bulging rolling soft wheel that employs an array of 16 folded-HASEL actuators as a mean for improved rolling performance. The actuators represent the soft components with discrete forces that propel the wheel, whereas the wheel's frame is rigid but allows for smooth, continuous change in position and speed. We discuss the interplay between the electrical and mechanical design choices, the modeling of the wheel's hybrid (continuous and discrete) dynamic behavior, and the implementation of a model predictive controller (MPC) for the robot's speed. With the balance of several design factors, we show the wheel's ability to carry integrated hardware with a maximum rolling speed at 0.7 m/s (or 2.2 body lengths per second), despite its total weight of 979 g, allowing the wheel to outperform the existing rolling soft wheels with comparable weights and sizes. We also show that the MPC enables the wheel to accelerate and leverage its inherent braking capability to reach desired speeds—a critical function that did not exist in previous rolling soft systems.

Soft robots compliment traditional rigid robots by expanding their capabilities to interact with the physical world. A robot made with compliant, soft materials can benefit from their inherent continuum mechanics to achieve interactions with the environment that a rigid robot may find difficult. This can include grasping delicate objects, navigating through variable terrain, or working alongside humans in a safer manner. The flexible, adaptable nature of soft robots provide these benefits, but they also make predicting their actuated response a difficult, computationally-intensive task. Here we provide a non-linear, reduced order model informed by collected data on hydraulically amplified self-healing electrostatic actuators (HASELs). With this reduced order model, we simulate robots comprised of multiple actuators in an effort to rapidly evaluate potential design candidates without the need for time-consuming manufacturing. The simulation leverages a reduced-order model of HASELs based on a parallel mass spring damper (MSD) representation, made of two non-linear springs, and a damper; this data-driven parameter identification aids model fidelity. We construct a robotic manipulator actuated via six HASELs and show that the simulations driven by the non-linear MSD models accurately predict the robot's physical behavior on a macro scale. While this work focuses on a specific actuator type, the approach shown here could be extended to other linearly expanding soft actuators. Using this method, soft robotic assemblies actuated via HASELs can be rapidly evaluated in simulation before a laborious manufacturing process, which in turn will allow for faster design iterations to create more effective robots.

Autonomous robots are comprised of actuation, energy, sensory, and control systems built from materials and structures that are not necessarily designed and integrated for multifunctionality. Yet, animals and other organisms that robots strive to emulate contain highly sophisticated and interconnected systems at all organizational levels, which allow multiple functions to be performed simultaneously. Herein, we examine how system integration and multifunctionality in nature inspires a new paradigm for autonomous robots that we call Embodied Energy. Currently, most untethered robots use batteries to store energy and power their operation. To extend operating times, additional battery blocks and supporting structures must be added, which increases weight and reduces efficiency. Recent advancements in energy storage techniques enable chemical or electrical energy sources to be embodied directly within the structures, materials, and mechanical systems used to create robots. This perspective highlights emerging examples of Embodied Energy, focusing on the design and fabrication principles of enduring autonomous robots.