Photolithographic Fabrication of Mechanically Adaptive Devices

Abstract

Water-responsive polymers, which enable the design of objects whose mechanical properties or shape can be altered upon moderate swelling, are useful for a broad range of applications. However, the limited processing options of materials that exhibit useful switchable mechanical properties generally restricted their application to objects having a simple geometry. Here we show that this problem can be overcome by using a negative photoresist approach in which a linear hydrophilic polymer is converted into a highly transparent cross-linked polymer network. The photolithographic process allows the facile production of objects of complex shape and permits programming of the cross-link density, the extent of aqueous swelling, and thereby the stiffness and refractive index under physiological conditions over a wide range and with high spatial resolution. Our findings validate a straightforward route to fabricate mechanically adaptive devices for a variety of (biomedical) uses, notably optogenetic implants whose overall shape, mechanical contrast, and optical channels can all be defined by photolithography.

Bilayer Bending Actuators Based on Semicrystalline Polyurethanes with Large Thermal‐Expansion Coefficients

“…Stimuli-responsive materials that can alter their shape and/or mechanical properties in response to an external stimulus are useful in drug delivery systems, [1] biomedical devices, [2][3][4][5] architectural components, [6] soft actuators, [7] soft robotics, [8] and other applications. Some of these materials and systems have been inspired by mechanically morphing structures found in nature, in which the hierarchical design principles are often the key to mechanical robustness and responsive behavior.…”