Real time high voltage capacitance for rapid evaluation of dielectric elastomer actuators.

Dielectric elastomer actuators (DEAs) are soft electromechanical transducers that have enabled robotic, haptic, and optical applications. Despite their advantages in high specific energy, large bandwidth, and simple fabrication, their widespread adoption is limited by poor long-term performance. While the mechanical work output has been studied extensively, the electrical energy input has rarely been characterized. Here we report a method to continuously monitor high voltage capacitance during DEA actuation to directly measure the electrical energy consumption. Our approach can track energy conversion efficiency, but also show changes in the device's properties in real-time. This unprecedented insight enables a novel way to study DEAs, evaluate degradation mechanisms, and correlate material structure to device performance. Moreover, it provides a data acquisition platform for data-driven optimization and prediction of long-term actuator performance. This work is a necessary step towards developing ultra-resilient DEAs and enabling a wide range of applications, from wearable devices to soft machines across different scales.

A Wearable Soft Haptic Communicator Based on Dielectric Elastomer Actuators.

Dielectric elastomer actuators exhibit an unusual combination of large displacements, moderate bandwidth, low power consumption, and mechanical impedance comparable with human skin, making them attractive for haptic devices. In this article, we propose a wearable haptic communication device based on a two-by-two array of dielectric elastomer linear actuators. We briefly describe the architecture of the actuators and their mechanical and electrical integration into a wearable armband. We then characterize the actuators' force, displacement, and thermal properties in a bench-top configuration. We also report on the power and drive circuit design. Finally, we perform a set of preliminary perception evaluations on participants using our haptic device, including detection threshold tests and identification tests for locations and directions on the forearm. Human testing with individual actuators demonstrates that the broadband actuation can be easily perceived on the forearm, providing the basis for both the development of a wearable actuator array and its use in more extensive perception evaluation as described herein.

Realizing the potential of dielectric elastomer artificial muscles.

Soft robotics represents a new set of technologies aimed at operating in natural environments and near the human body. To interact with their environment, soft robots require artificial muscles to actuate movement. These artificial muscles need to be as strong, fast, and robust as their natural counterparts. Dielectric elastomer actuators (DEAs) are promising soft transducers, but typically exhibit low output forces and low energy densities when used without rigid supports. Here, we report a soft composite DEA made of strain-stiffening elastomers and carbon nanotube electrodes, which demonstrates a peak energy density of 19.8 J/kg. The result is close to the upper limit for natural muscle (0.4-40 J/kg), making these DEAs the highest-performance electrically driven soft artificial muscles demonstrated to date. To obtain high forces and displacements, we used low-density, ultrathin carbon nanotube electrodes which can sustain applied electric fields upward of 100 V/µm without suffering from dielectric breakdown. Potential applications include prosthetics, surgical robots, and wearable devices, as well as soft robots capable of locomotion and manipulation in natural or human-centric environments.

Multilayer Dielectric Elastomers for Fast, Programmable Actuation without Prestretch.

A novel method for the fabrication of dielectric elastomer actuators (DEAs) combines acrylic polymers and single wall carbon nanotube network electrodes. DEAs made using this technique do not require prestretching, have extremely thin electrodes, and can be actuated at low voltage. The method is applied to create a multimorph device with nine actuation modes based on just four inputs.

Skeletal diversity through radical cyclization of tetrahydropyridine scaffolds.

Suitably functionalized tetrahydropyridines (methyl pipecolates) have been used as conformationally biased templates for radical cyclizations to access benzoisoquinuclidines and linearly fused indenopiperidines. Variation of skeletal types is determined by location of a radical-initiating element.