James M. Chwalek

A new method for deflecting liquid microjets

A new method is reported for deflecting a microscopic jet emanating from a nozzle away from the nozzle’s axis of symmetry. It relies on putting energy into the jet through an asymmetric heater embedded in the nozzle. This novel phenomenon is probed theoretically. It is shown that jet deflection is set by the competition among three effects. Two of these can be attributed to the variation with temperature of surface tension and the third to that of viscosity. Whether the contact line is fixed or free is shown to profoundly impact the extent of jet deflection at a given flow rate.

Micro-jet nozzle array for precise droplet metering and steering having increased droplet deflection

We present the architecture and fabrication method of a fluidic device with increased droplet deflection. The device is capable of producing picoliter size droplets precisely and steering them. The precision is a consequence of the reproducibility of the nozzles that are made using VLSI technology and tools. In addition, the droplet size is determined by the precise timing of applied heat pulses. We present both experimental and modeling results.

Upconverting Tm3+ doped Ba–Y–Yb–F thin film waveguides for visible and ultraviolet light sources

We report the results of Tm3+ doped Ba–Y–Yb–F thin film planar waveguides in glassy form, which produced red, green, blue, and ultraviolet upconverted luminescence when pumped by infrared radiation at λ=960 nm. The films of nominal composition BaYYbF8 doped with 1% Tm have been deposited with both thermal and e‐beam evaporation techniques on substrates of fused silica, Si, and GaAs. Planar waveguiding was demonstrated for the films deposited on fused silica. Optimal deposition conditions with respect to the ability of the films to produce upconverted luminescence and low propagation loss are discussed.

MEMS-Based Microfluidic Devices

Micro-Electro-Mechanical Systems (MEMS) technology can be integrated with microfluidic functionality to enable the generation of microdrops with unprecedented throughput and precise control of drop volume, speed, and placement. The most prominent examples of microdrop generators are in the field of inkjet printing where printheads with thousands of nozzles produce steady streams of microdrops at kilohertz repetition rates. In this paper, we discuss a proposed MEMS-based microfluidic drop generator that operates on the basis of a thermally induced Marangoni effect. We describe the physics of droplet generation and discuss operating performance relative to the fluid rheology, thermal modulation, and wavelength dependencies.© 2010 ASME

Forced TM-mode operation of a GaAlAs laser diode by use of annealed proton-exchanged LiNbO(3) and LiTaO(3) waveguides.

Forced TM-mode operation of GaAlAs laser diode by use of annealed proton-exchanged LiNbO(3) and LiTaO(3) waveguides as the polarizing element in an external cavity is demonstrated. The results are compared with those for an external cavity that uses a bulk polarizer. The dependence of such factors as the amount and polarization of the feedback in these external cavity configurations is discussed.