Kirigami‐Inspired Self‐Assembly of 3D Structures

Abstract

Self‐assembly of 3D structures presents an attractive and scalable route to realize reconfigurable and functionally capable mesoscale devices without human intervention. A common approach for achieving this is to utilize stimuli‐responsive folding of hinged structures, which requires the integration of different materials and/or geometric arrangements along the hinges. It is demonstrated that the inclusion of Kirigami cuts in planar, hingeless bilayer thin sheets can be used to produce complex 3D shapes in an on‐demand manner. Nonlinear finite element models are developed to elucidate the mechanics of shape morphing in bilayer thin sheets and verify the predictions through swelling experiments of planar, millimeter‐scaled PDMS (polydimethylsiloxane) bilayers in organic solvents. Building upon the mechanistic understandings, The transformation of Kirigami‐cut simple bilayers into 3D shapes such as letters from the Roman alphabet (to make “ADVANCED FUNCTIONAL MATERIALS”) and open/closed polyhedral architectures is experimentally demonstrated. A possible application of the bilayers as tether‐less optical metamaterials with dynamically tunable light transmission and reflection behaviors is also shown. As the proposed mechanistic design principles could be applied to a variety of materials, this research broadly contributes toward the development of smart, tetherless, and reconfigurable multifunctional systems.

3D Self‐Assembled Microelectronic Devices: Concepts, Materials, Applications

“…Bassik et al later investigated the effects of both pH and ionic strength of liquids, and showed a reversible folding and unfolding of hydrogel (Figure b) bilayer structures and hinges by cycling the pH and ionic strength of the liquid environment. A bilayer made from the same material, poly(ethylene glycol), but with two different crosslink densities was demonstrated by Jamal et al to work just as a well, and similar results were shown using PDMS bilayers by Abdullah et al Yoon et al employed a continuous crosslink gradient within a single hydrogel layer (Figure e) with a low intensity exposure to induce the swelling differential across its thickness, and used it to act as a hinge actuator to self‐assemble various polyhedra. In our previous works, we specially developed novel lithographically patternable system of polymers based on sacrificial layer, hydrogel layer and polyimide.…”

“…These grippers did not require any wires, tethers, or batteries to accomplish self‐folding with angles over 100° and radii as small as 765 nm . Abdullah et al also demonstrated the possibilities of achieving gripper‐like configurations on‐demand from simple planar bilayers that do not require hinges for actuation (Figure e) . Applying liquid crystalline materials, Schuhladen et al could actuate an optical aperture changing the effective opening of the artificial iris from 10% to 90% with promising applications in ocular implants.…”

“…Jeong et al spatially patterned areas of silicone and polyurethane to direct the swelling in hexane (Figure c), demonstrating coils, helices, and polyhedra when used as a swelling hinge actuator. Abdullah et al swelled a PDMS bilayer based on different crosslink densities using a 1‐propanol/xylene mixture to form grippers. Vapor phase swelling of a PDMS (Figure d) and an oxygen‐plasma‐induced oxide bilayer was reported by Gómez et al…”

Electroactive Silk Fibroin Films for Electrochemically Enhanced Delivery of Drugs

“…For many biomedical applications in vitro, ex vivo and in vivo, the ability to deliver active ingredients in a controlled fashion is very appealing, and many stimuli have been investigated to achieve this (e.g., ionic strength, light, magnetic fields, pH, ultrasound, etc. ), [ 12,17–20 ] and a variety of stimuli‐responsive silk‐based materials have been reported. [ 21–28 ]…”

Thermoresponsive Three‐Stage Optical Modulation of a Self‐Healing Composite Hydrogel

“…Smart materials, especially hydrogels, that can respond to external environmental stimulus open new access to applications including soft robotics, smart actuators, and wound dressing . All of these require the materials to have intrinsically tunable optical or mechanical properties while facing external stimuli such as light, pH, ionic strength, and temperature.…”