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.

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.

A conventional light management approach on a photo-catalyst is to concentrate photo-intensity to enhance the catalytic rate. We present a counter-intuitive approach where light intensity is distributed below the electronic photo-saturation limit under the principle of light maximization. By operating below the saturation point of the photo-intensity induced hydroxide growth under reactant gaseous H2+CO2 atmosphere, a coating of defect engineered In2O3-x(OH)y nanorod Reverse Water Gas Shift solar-fuel catalyst on an optical waveguide outperforms a coated plane by a factor of 2.2. Further, light distribution along the length of the waveguide increases optical pathlengths of the weakly absorptive green and yellow wavelengths, which increases CO product rate by a factor of 8.1-8.7 in the visible. Synergistically pairing with thinly doped silicon on the waveguide enhances the CO production rate by 27% over the visible. In addition, the persistent photoconductivity behavior of the In2O3-x(OH)y system enables CO production at a comparable rate for 2 h after turning off photo-illumination, enhancing yield with 44-62% over thermal only yield. The practical utility of persistent photocatalysis was demonstrated through outdoor solar concentrator tests, which after a day-and-night cycle showed CO yield increase of 19% over a day-light only period.

sequestration. [5][6][7] There are three categories of techniques that have been used to manufacture TMPs; the first (canonical) category relies on photo-or electron-beam (e-beam) lithography and etching. These methods permit unparalleled flexibility in user determination of feature size and spatial positioning, but they are expensive, require a cleanroom (and are not accessible to all users), and have some limitations on throughput (particularly for e-beam lithography). 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. [12,13] These techniques are useful, but they also rely on expensive and specialized tools and well-trained personnel, and can have limited throughput.A third category of "wet" cleanroom-free techniques has recently been proposed for forming topographical micropatterns, relying on dielectrophoresis tweezers (DEPT), [14][15][16] acoustic tweezers (AT), [17][18][19] magnetic tweezers (MT), [20,21] and optical tweezers (OT). [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. But each of the individual techniques has disadvantages; for example, DEPT and AT require the manufacture of micropatterned electrodes (typically using canonical cleanroom methods) and lack the flexibility to pattern large numbers of features. Likewise, MT-based methods can only assemble micro-objects that respond to magnetic fields, and OT-based techniques have sub-nanoNewton (

Metal-dielectric multilayers are versatile optical devices that can be designed to combine the visible transmittance of dielectrics with the electronic properties of metals for plasmonic and meta-material applications. However, their performances are limited by an interfacial optical absorption often attributed entirely to the metal surface roughness. Here, we show that during deposition of AlN/Ag/AlN and SiNx/Ag/SiNx multilayers, significant diffusion of Ag into the top dielectric layer form Ag nanoparticles which excite localized surface plasmon resonances that are primarily responsible for the interfacial optical absorption. Based on experimental depth profiles, we model the multilayer’s silver concentration profile as two complementary error functions: one for the diffused Ag nanoparticles and one for the interface roughness. We apply the Maxwell-Garnett and Bruggeman effective medium theories to determine that diffusion characteristics dominate the experimental absorption spectra. The newfound metal nanoparticle diffusion phenomenon effectively creates a hybrid structure characteristic of both metal-dielectric multilayer and metal-dielectric composite.