Opto-Thermophoretic Manipulation and Construction of Colloidal Superstructures in Photocurable Hydrogels

Abstract

Light-based manipulation of colloidal particles holds great promise in fabrication of functional devices. Construction of complex colloidal superstructures using traditional optical tweezers is limited by high operation power and strong heating effect. Herein, we demonstrate low-power opto-thermophoretic manipulation and construction of colloidal superstructures in photocurable hydrogels. By introducing cationic surfactants into a hydrogel solution under a light-directed temperature field, we create both thermoelectric fields and depletion attraction forces to control the suspended colloidal particles. The particles of various sizes and compositions are thus trapped and organized into various superstructures. Furthermore, the colloidal superstructures are immobilized and patterned onto solid-state substrates through UV-induced photopolymerization of the hydrogel. Our opto-thermophoretic technique will open up avenues for bottom-up assembly of colloidal materials and devices.

3D Nanophotonic device fabrication using discrete components

“…The generated force can be the optical force from the beam itself or an induced force at an interface. The main variants of LDA include techniques such as opto-electronic tweezers (OET) [82][83][84][85], opto-thermophoretic tweezers (OTT) [86][87][88][89][90][91][92], bubble pen lithography (BPL) [93][94][95][96], and optical tweezers (OT) [97][98][99][100][101][102][103][104][105][106][107][108][109][110][111]. The first three listed techniques-OET, OTT, and BPL-rely on the presence of a substrate to generate the required force.…”

“…In the case of OTT (Figure 7D), the main requirement for the sample chamber is an optothermally responsive bottom substrate, such as a thin layer of metal. A laser illuminates the metal film, leading to localized heating, which establishes a thermal gradient in the sample cell exerting a thermophoretic force on objects in the cell [88][89][90]. In BPL ( Figure 7E), a laser beam is focused on to a plasmonic substrate with sufficient energy to form a microbubble on the surface.…”

Digital Assembly of Colloidal Particles for Nanoscale Manufacturing

“…e) 2D hybrid assembly of a 5 µm PS sphere surrounded with four 2 µm silica spheres. Adapted with permission . Copyright 2018, American Chemical Society .…”

“…[104] An extension of OTA, which uses photocurable hydrogels to immobilize particles instead of the depletion attraction, has also been proposed for assembly of particles. [108] The trapping and manipulation mechanism is similar to original OTA except that the particle solution consists of a photocurable polymer such as polyethylene glycol diacrylate in addition to the CTAC as shown in Figure 4a. The nanoparticles are initially trapped and assembled into a specified superstructure and subsequently immobilized using UV-induced photopolymerization as illustrated in Figure 4b.…”

“…An extension of OTA, which uses photocurable hydrogels to immobilize particles instead of the depletion attraction, has also been proposed for assembly of particles . The trapping and manipulation mechanism is similar to original OTA except that the particle solution consists of a photocurable polymer such as polyethylene glycol diacrylate in addition to the CTAC as shown in Figure a.…”