Stimuli‐Responsive Liquid Crystal Printheads for Spatial and Temporal Control of Polymerization

Abstract

decompose an azo initiator). [2,16] Another strategy is to sequester reagents for polymerization within nano-or microcapsules [17][18][19] that release their contents upon arrival of targeted stimuli, such as redox or mechanical cues (stress/fracture/damage/ self-healing, etc.). [17,19] Here we report an approach to achieving spatially and temporally controlled polymerization in response to a range of cues by using initiator loaded stimuli-responsive liquid crystals (LCs).Our approach is inspired by the success of stereolithographic technologies for the fabrication of 3D polymeric structures. [3][4][5]20,21] Conventional stereolithography involves the rastering of a light beam across a solution containing monomer and initiator to control the time and the location of polymerization. [20,21] This permits additive assembly of a wide range of complex 3D microstructures but is limited to photoinitiation of the polymerization process. The principles developed herein provide a first step towards a technology that permits spatial and temporal control over the synthesis of polymeric structures in response to local chemical cues. The approach involves sequestering initiators for polymerization within LCs, and uses the well-known stimuli-responsive properties of LCs to program ejection of the initiator into solution at a desired time and location to synthesize a targeted polymeric structure.

Liquid Crystalline Systems from Nature and Interaction of Living Organisms with Liquid Crystals

“…In addition, the stimuli-triggered reorientation of directors modulates forces acting on the guest materials within LCs, so one can introduce additional functionalities into the LC-based biosensor (e.g., self-regulated release of drug, self-regulated polymerization). [7,132] Recently, the LC-based sensors have been integrated with metasurface (MS) to overcome challenges in metahologram. The LC-MS system realizes the new class of interactive metahologram that autonomously sense a target stimulus (e.g., electric field, toxic gas, pressure, temperature) and instantaneously change holographic images that were not available in previous systems.…”

Advancements in droplet reactor systems represent new opportunities in chemical reactor engineering: A perspective

“…Because of their intrinsic properties, including maintaining mixtures of positional and orientational order in various mesophases, [167] immobilized LCs have been exploited for a variety of applications, including display technology, [168,169] sensors, [170][171][172][173][174][175][176] particle self-assembly, [177][178][179][180][181][182][183][184][185] molecular assembly [186][187][188] and synthesis, [189][190][191][192][193][194] and activating the release of cargo. [195][196][197][198][199][200][201] Very recently, our group reported a class of LC-infused porous surfaces as advanced open anisotropic liquid surfaces for droplet reactors (Figure 14A). [113] An important feature for the design of this open surface is the ability to manipulate the chemical compositions of resting droplets through controlling the chemical release from open functional surface to droplets.…”

Stimuli-Responsive Materials from Liquid Crystals

“…To this end, X. Wang et al use a miniwell of LCs as a printhead (Figure 7e). 99 Aqueous microdroplets containing a polymerization initiator (ammonium persulfate, APS) are sequestered in the LCs and decorated with anionic amphiphiles (SDS). The printhead is then placed in an aqueous bath containing monomers (Nisopropylacrylamide, NIPAm) and a polymerization accelerator (N,N,N′,N′-tetramethylethylenediamine, TEMED).…”

“…Copyright 2022 John Wiley and Sons. (e) Reproduced with permission from ref . Copyright 2022 John Wiley and Sons.…”