Holographic optical assembly and photopolymerized joining of planar microspheres

Abstract

The aim of this research is to demonstrate a holographically driven photopolymerization process for joining colloidal particles to create planar microstructures fixed to a substrate, which can be monitored with real-time measurement. Holographic optical tweezers (HOT) have been used to arrange arrays of microparticles prior to this work; here we introduce a new photopolymerization process for rapidly joining simultaneously handled microspheres in a plane. Additionally, we demonstrate a new process control technique for efficiently identifying when particles have been successfully joined by measuring a sufficient reduction in the particles' Brownian motion. This technique and our demonstrated joining approach enable HOT technology to take critical steps toward automated additive fabrication of microstructures.

Optical tweezers: theory and practice

“…Holographic optical tweezers have been successfully used to precisely manipulate hybrid block copolymer to create ordered customisable arrays of complex structures speeding up a normally slow processes [162], Shaw and co-workers combined a new photopolymerisation process for rapidly joining simultaneously microspheres assembled in a planar structure by a HOT [163].…”

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

“…49 To estimate the trapping stability, we conducted Gaussian fitting for the histogram of the particle displacements, which gives a variance σ of ~15 nm in both the x and y directions, corresponding to a trapping stiffness κ of ~37 pN/ μ m (κ=2kBTσ2). To generate the same trapping stiffness for a 500 nm PS sphere, optical tweezers typically require a power of ~100 mW, 23,46 which is 3 orders of magnitude higher than the working power (0.23 mW) of our opto-thermophoretic tweezers.…”

“…21–31 One strategy is to trap and assemble particles into superstructures with optical tweezers and to immobilize the assembled superstructures through van der Waals forces 24,25 or chemical linkages such as photopolymerization. 21,23 Conventional optical tweezers require high power, which may cause irreversible photodamage to the colloidal particles. 32 Optical printing based on plasmon-enhanced optical radiation force is a low-power technique for precise patterning of plasmonic nanoparticles; however, plasmonic heating of already fixed nanoparticles prevents the assembly of particle dimers and clusters in near-field coupling regime.…”

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.…”

“…While OT can effectively position a diverse array of objects in 3D, it is necessary to immobilize these objects in the absence of the optical trap to form self-standing structures. This has been achieved using several approaches, including biochemical binding [101,125,128,132,140], colloidal engineering [102,129], and photopolymerization [98,103,141].…”