Differentially photo-crosslinked polymers enable self-assembling microfluidics

Abstract

An important feature of naturally self-assembled systems such as leaves and tissues is that they are curved and have embedded fluidic channels that enable the transport of nutrients to, or removal of waste from, specific three-dimensional (3D) regions. Here, we report the self-assembly of photopatterned polymers, and consequently microfluidic devices, into curved geometries. We discovered that differentially photo-crosslinked SU-8 films spontaneously and reversibly curved upon film de-solvation and re-solvation. Photolithographic patterning of the SU-8 films enabled the self-assembly of cylinders, cubes, and bidirectionally folded sheets. We integrated polydimethylsiloxane (PDMS) microfluidic channels with these SU-8 films to self-assemble curved microfluidic networks.

Cracking-assisted photolithography for mixed-scale patterning and nanofluidic applications

“…In general, cracks are initiated when a stiff and thin elastic layer placed on a viscoelastic underlying layer is subjected to tensile stresses higher than its fracture strength 15,16 . In the present work, the elastic and viscoelastic layers were formed by exposing the same spincoated photoresist (10-mm thick) to ultraviolet light without using the i-line filters recommended by the manufacturer to enable uniform cross-linking throughout the thickness 17 . This delicate process produced a relatively stiff and elastic layer onto a viscoelastic layer with a cross-linking gradient along the direction normal to the substrate, namely a silicon wafer (Fig.…”

Three-dimensional shape transformations of hydrogel sheets induced by small-scale modulation of internal stresses

“…One of the approaches to the design of such materials utilizes the generation of non-uniform internal stresses [5][6][7][8][9][10][11][12] . In the past decade, bending and folding of soft elastic sheets have been achieved by inducing gradients in swelling across the sheet thickness 11 .…”

Compact helical antenna for smart implant applications

“…Techniques relying on differentially strained photopatternable SU8 in combination with metal patterning have already been introduced. 43 To produce arrays of normal mode helical antennas over large areas with high yield and allow for their encapsulation, we developed a strain engineering platform relying on photopatternable, thermally and chemically stable imide-and acrylic-based polymers. Furthermore, we precisely define the combination of different processing steps and the material combinations in exactly the right order, allowing us to achieve highyield production of compact normal mode helical antennas over large areas in a cost-and time-efficient self-assembly process.…”