Grayscale gel lithography for programmed buckling of non-Euclidean hydrogel plates

Abstract

Shape programmable materials capable of morphing from a flat sheet into controlled three dimensional (3D) shapes offer promise in diverse areas including soft robotics, tunable optics, and bio-engineering. We describe a simple method of 'grayscale gel lithography' that relies on a digital micromirror array device (DMD) to control the dose of ultraviolet (UV) light, and therefore the extent of swelling of a photocrosslinkable poly(N-isopropyl acrylamide) (PNIPAm) copolymer film, with micrometer-scale spatial resolution. This approach allows for effectively smooth profiles of swelling to be prescribed, enabling the preparation of buckled 3D shapes with programmed Gaussian curvature.

Ultrafast Digital Printing toward 4D Shape Changing Materials

“…[25] Specifically, the use of commercial liquid monomers in the current work instead of a custom made pre-polymer as the printing precursor has several critical advantages besides the obvious material availability and cost. Since the initiator is not an integral part of the pre-polymer, it can be chosen freely to better accommodate the light source, thus permitting the use of safe visible light instead of ultraviolet light curing required for the pre-polymer.…”

Contrasting bending energies from bulk elastic theories

“…Much recent work in soft matter mechanics has explored the interplay of stretching and bending elasticity in incompatible plates and shells composed of isotropic gels or elastomers, or nematic solids [1][2][3][4][5]. This subject has inspired, among other things, fundamental questions about embeddings [6][7][8], design principles for shape-programmable materials [9][10][11][12], and insight into the complex shapes of leaves and torn plastic trash bags [13,14].…”

Photolithographically Patterned Hydrogels with Programmed Deformations

“…are severallithographic strategies using X-ray,gamma-ray,electron beam,a nd photo [57][58][59][60][61][62][63] to trigger the formation or modification of an etwork at programmed regions.T he photo-initiated polymerization and crosslinking is mostc ommonly used to preparep atterned hydrogels, because (i)light is ac lean energy to trigger the reaction of monomer,o ligomer,o rp olymer,( ii) light is relatively cheap and safe, when compared to X-ray and gamma-ray,( iii)the reaction can be facilely controlled at specific regions with spatial precisionw hen guided by ap hoto mask, (iv) the methodc an generate large-area gel patterns with high fidelity and various features, and (v) multiple step patterning can be realized thanks to the open network of gel, which enables precursor solutiont od iffuse in for subsequent photo-triggered reactiona nd unreacted reagents to be removed.T his methodc an produce hydrogels with desirable size and features at specific regions or control the distribution of one component in another gel matrix. [64][65][66][67][68] Patterned hydrogels have numerousa pplicationso wing to the rich functionalities of patterned polymers and aw ide range of applicationso ft he patterns.…”

“…Smooth profiles of crosslinking density and thuss welling ratio gradient can be encoded in the hydrogels by using ag rayscale lithographic mask. [63] This versatile strategye nables the designingo fa rbitrary 2D patterns with controlled swelling mismatch and thus programmable deformations to form complex configurations like Enneper's minimal surfaces.…”