Gas-phase microactuation using kinetically controlled surface states of ultrathin catalytic sheets

Abstract

Biological systems convert chemical energy into mechanical work by using protein catalysts that assume kinetically controlled conformational states. Synthetic chemomechanical systems using chemical catalysis have been reported, but they are slow, require high temperatures to operate, or indirectly perform work by harnessing reaction products in liquids (e.g., heat or protons). Here, we introduce a bioinspired chemical strategy for gas-phase chemomechanical transduction that sequences the elementary steps of catalytic reactions on ultrathin (<10 nm) platinum sheets to generate surface stresses that directly drive microactuation (bending radii of 700 nm) at ambient conditions (T = 20 °C; P total = 1 atm). When fueled by hydrogen gas and either oxygen or ozone gas, we show how kinetically controlled surface states of the catalyst can be exploited to achieve fast actuation (600 ms/cycle) at 20 °C. We also show that the approach can integrate photochemically controlled reactions and can be used to drive the reconfiguration of microhinges and complex origami- and kirigami-based microstructures.

Actuation for flexible and stretchable microdevices

“…Chemical actuation refers to the use of materials that can undergo controlled strokes and forces in response to chemical stimulations, such as pH change, 120 surface catalysis, 46 moisture gradient, 139,140 organic solvent stimulations, 141 oscillatory Belousov–Zhabotinsky chemical reaction in hydrogel, 142 and chemical combustion. 143 Chemical stimulation through pH change can actuate materials that exhibit reversible deformations under alkaline and acidic solutions, 120 Fig.…”

“…This paper aims to systematically review the state-of-art actuation mechanisms for flexible and stretchable microdevices. We first elaborate on the fundamental working principle of different actuation mechanisms based on power sources of pneumatic, 41 hydraulic, 36 thermal, 42 electrical, 43 magnetic, 44 humidity, 45 chemical, 46 mechanical, 47 etc. The structure designs, characteristics, and performance of various actuators are discussed and compared.…”

Mechanically-Guided 3D Assembly for Architected Flexible Electronics

“…Flexible electronic devices in polyhedral forms are usually manufactured using folding assembly methods. 172,181 Polyhedral forms, such as pyramids and cubes, stand as a typical type of spatial configuration that can facilitate structural functionalities involving capturing, 125,134,184,295,316−318 sensing, 294,296,298,319 light emitting, 297,320 and the rest. Through the folding of patterned bilayer thin films, microgrippers were manufactured enabling controlled captures (e.g., folding angles) of single cells (Figure 14a).…”

“…Flexible electronics with architected 3D configurations can better mimic and conform to the structural forms of natural species with complex spatial geometries, when compared to those in planar device structures. This section reviews diverse 3D forms of flexible electronics manufactured using mechanically-guided assembly methods, including 3D arc-shaped forms, ,,,,,− 3D helical forms, ,,,,,, tubular forms, ,,,− polyhedral forms, ,,− hemispherical forms, ,,,,,,,,,,− conformally wrapping forms ,,,,,,,− and other complex 3D forms, ,,,,,,, through summarizing and discussing the representative functional devices that benefit from their unique structural characteristics.…”

“…Flexible electronic devices in polyhedral forms are usually manufactured using folding assembly methods. , Polyhedral forms, such as pyramids and cubes, stand as a typical type of spatial configuration that can facilitate structural functionalities involving capturing, ,,,,− sensing, ,,, light emitting, , and the rest.…”