Patterned Optoelectronic Tweezers: A New Scheme for Selecting, Moving, and Storing Dielectric Particles and Cells

Abstract

Optical micromanipulation has become popular for a wide range of applications. In this work, a new type of optical micromanipulation platform, patterned optoelectronic tweezers (p‐OET), is introduced. In p‐OET devices, the photoconductive layer (that is continuous in a conventional OET device) is patterned, forming regions in which the electrode layer is locally exposed. It is demonstrated that micropatterns in the photoconductive layer are useful for repelling unwanted particles/cells, and also for keeping selected particles/cells in place after turning off the light source, minimizing light‐induced heating. To clarify the physical mechanism behind these effects, systematic simulations are carried out, which indicate the existence of strong nonuniform electric fields at the boundary of micropatterns. The simulations are consistent with experimental observations, which are explored for a wide variety of geometries and conditions. It is proposed that the new technique may be useful for myriad applications in the rapidly growing area of optical micromanipulation.

Assembly of Topographical Micropatterns with Optoelectronic Tweezers

“…Figure 1a is a schematic of the OET devices used in this work, which comprise a top and a bottom plate, each coated on one side with conductive, transparent indium tin oxide (ITO). [35,40,41] OET devices were assembled by joining the top and bottom plates together with a spacer to form a chamber (Figure 1c), within which the manipulation of microparticles was performed. [35,40,41] OET devices were assembled by joining the top and bottom plates together with a spacer to form a chamber (Figure 1c), within which the manipulation of microparticles was performed.…”

“…As shown in Figure 2b (extracted from Movie S1, Supporting Information), a light pattern is projected onto the suspension of particles-in this case, a mirror image of the abbreviation, "OET." [40] Thus, when handling polystyrene particles, the light patterns were projected as a "negative" of the intended TMP. The CM factor for polystyrene microbeads in the conditions used here results in negative DEP force, such that the particles are repelled from the illuminated region and accumulate in the dark region.…”

“…[40,41] When completed, devices comprised a 20 µL chamber sandwiched between a top and bottom plate (each plate bearing a 200-nm-thick ITO electrode), with the bottom plate featuring a 1 µm thick layer of a-Si:H deposited by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). [40,41] When completed, devices comprised a 20 µL chamber sandwiched between a top and bottom plate (each plate bearing a 200-nm-thick ITO electrode), with the bottom plate featuring a 1 µm thick layer of a-Si:H deposited by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD).…”

“…In recognition of these limitations, a second category of "dry" cleanroom-free methods has been developed, including 3D printing, [8][9][10] laser machining, [11] and "pick-and-place" technologies. [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] The new method is a member of the wet cleanroom-free assembly techniques, but lacks many of the limitations indicated previously. [22][23][24][25] These techniques, in which patterns of 3D particles are assembled in a fluidic environment and are later dried for use in TMP applications, are creative and interesting, and preserve many of the advantages of the canonical methods while allowing for accessible, cleanroom-free operation.…”

“…[26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] The new method is a member of the wet cleanroom-free assembly techniques, but lacks many of the limitations indicated previously. [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] The new method is a member of the wet cleanroom-free assembly techniques, but lacks many of the limitations indicated previously.…”