Escape from an Optoelectronic Tweezer Trap: experimental results and simulations

Abstract

Optoelectronic tweezers (OET) are a microsystem actuation technology capable of moving microparticles at mm s velocities with nN forces. In this work, we analyze the behavior of particles manipulated by negative dielectrophoresis (DEP) forces in an OET trap. A user-friendly computer interface was developed to generate a circular rotating light pattern to control the movement of the particles, allowing their force profiles to be conveniently measured. Three-dimensional simulations were carried out to clarify the experimental results, and the DEP forces acting on the particles were simulated by integrating the Maxwell stress tensor. The simulations matched the experimental results and enabled the determination of a new "hopping" mechanism for particle-escape from the trap. As indicated by the simulations, there exists a vertical DEP force at the edge of the light pattern that pushes up particles to a region with a smaller horizontal DEP force. We propose that this phenomenon will be important to consider for the design of OET micromanipulation experiments for a wide range of applications.

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.…”

“…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.…”

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

“…We next turned our attention to more complex p‐OET “traps” in which devices were patterned to feature a‐Si:H projections surrounded by exposed ITO ( Figure a). A 3D model was developed to simulate this system, with length ( X ‐axis) and width ( Y ‐axis) set to 250 µm and height ( Z ‐axis) set to 150 µm (Section S4, Supporting Information). Electric potential and electric field distributions were simulated and are shown in Figure b,c, respectively ( XY ‐slices at Z = 1.3 µm,, i.e., for a bead located 0.1 µm above the a‐Si:H layer).…”

Nanoscale integration of single cell biologics discovery processes using optofluidic manipulation and monitoring

“…In turn, objects such as particles or cells, experience dielectrophoresis (DEP) force in the presence of the light‐induced electric‐field gradient. The force applied to a particle with radius is proportional to the electric field applied (Zhang, Nikitina et al, ). The force can be positive (attractive) or negative (repulsive) depending on the relative values of the complex permittivity of the media and particle (Q. Chen & Yuan, ).…”