A Biomimetic Approach to Increasing Soft Actuator Performance by Friction Reduction

Review: Sensors for Biosignal/Health Monitoring in Electronic Skin

Skin is the largest sensory organ and receives information from external stimuli. Human body signals have been monitored using wearable devices, which are gradually being replaced by electronic skin (E-skin). We assessed the basic technologies from two points of view: sensing mechanism and material. Firstly, E-skins were fabricated using a tactile sensor. Secondly, E-skin sensors were composed of an active component performing actual functions and a flexible component that served as a substrate. Based on the above fabrication processes, the technologies that need more development were introduced. All of these techniques, which achieve high performance in different ways, are covered briefly in this paper. We expect that patients' quality of life can be improved by the application of E-skin devices, which represent an applied advanced technology for real-time bio- and health signal monitoring. The advanced E-skins are convenient and suitable to be applied in the fields of medicine, military and environmental monitoring.

Antagonist Concepts of Polypyrrole Actuators: Bending Hybrid Actuator and Mirrored Trilayer Linear Actuator

Following the natural muscle antagonist actuation principle, different adaptations for "artificial muscles" are introduced in this work. Polypyrrole (PPy) films of different polymerization techniques (potentiostatic and galvanostatic) were analyzed and their established responses were combined in several ways, resulting in beneficial actuation modes. A consecutive "one-pot" electrosynthesis of two layers with the different deposition regimes resulted in an all-PPy bending hybrid actuator. While in most cases the mixed-ion activity of conductive polymers has been considered a problem or a drawback, here for the first time, the nearly equal expansions upon oxidation and reduction of carefully selected conditions further allowed to fabricate a "mirrored" trilayer laminate, which behaved as a linear actuator.

A Kirigami Approach of Patterning Membrane Actuators

Ionic electroactive polymer actuators are typically implemented as bending trilayer laminates. While showing high displacements, such designs are not straightforward to implement for useful applications. To enable practical uses in actuators with ionic electroactive polymers, membrane-type film designs can be considered. The significantly lower displacement of the membrane actuators due to the lack of freedom of motion has been the main limiting factor for their application, resulting in just a few works considering such devices. However, bioinspired patterning designs have been shown to significantly increase the freedom of motion of such membranes. In this work, we apply computer simulations to design cutting patterns for increasing the performance of membrane actuators based on polypyrrole doped with dodecylbenzenesulfonate (PPy/DBS) in trilayer arrangements with a polyvinylidene fluoride membrane as the separator. A dedicated custom-designed device was built to consistently measure the response of the membrane actuators, demonstrating significant and pattern-specific enhancements of the response in terms of displacement, exchanged charge and force.