Electrospraying and ultraviolet light curing of nanometer-thin polydimethylsiloxane membranes for low-voltage dielectric elastomer transducers

Abstract

Dielectric elastomer transducers (DETs) have attracted interest as actuators, sensors, and even as self-sensing actuators for applications in medicine, soft robotics, and microfluidics. To reach strains of more than 10 %, they currently require operating voltages of several hundred volts. In medical applications for artificial muscles, however, their operation is limited to a very few tens of volts, which implies high permittivity materials and thin-film structures. Such micro-or nanostructures can be prepared using electro-spraying, a cost-effective technique that allows upscaling using multiple nozzles for the fabrication of silicone films down to nanometer thickness. Deposition rates of several micrometers per hour have already been reached. It has been recently demonstrated that such membranes can be fabricated by electro-spraying and subsequent ultraviolet light irradiation. Herein, we introduce a relatively fast deposition of a dimethyl silicone copolymer fluid that contains mercaptopropyl side chains in addition to the methyl groups. Its elastic modulus was tuned with the irradiation dose of the 200 W Hg-Xe lamp. We also investigated the formation of elastomer films, using polymer concentrations in ethyl acetate of 1, 2, 5 and 10 vol%. After curing, the surface roughness was measured by means of atomic force microscopy. This instrument also enabled us to determine the average elastic modulus out of, for example, 400 nanoindentation measurements, using a spherical tip with a radius of 500 nm. The elastomer films were cured for a period of less than one minute, a speed that makes it feasible to combine electro-spraying and in situ curing in a single process step for fabricating low-voltage, multilayer DETs.

In vitro testing of an artificial muscle for the treatment of incontinence

“…23 There are several attempts with limited progress to realise artificial sphincters on the basis of electroactive polymer actuators and devices, see e.g. [27][28][29][30][31][32][33][34][35][36] So far, HASEL technology has not been considered for the implementation into artificial sphincters for severe incontinence treatment. Therefore, the present study focuses on the HASEL principle for artificial muscles with the aim to demonstrate feasibility.…”

Nanomechanical probing of thin-film dielectric elastomer transducers

“…30 As reported previously, the nanometer-thin Au electrode is not confluent and forms nanoclusters with a nominal size of (20 6 10) nm. 31 NI results on actuated DETs operated at voltages of U ¼ 0, 40, 80, 120, and 160 V are summarized in Table I for applied loads of P ¼ 25, 50, 75, and 100 nN. The resulting mean indentation depth d including the measurements at U ¼ 0 V were fitted using a Gaussian function.…”