Microfluidic devices fabricated by microelectromechanical systems (MEMS) and rapid-prototyping technology are becoming prevalent in biological and medical applications. An important application is sorting of cells and embryos in devices that combine fluidics, mechanics, optics and electronics to identify, manipulate, and sort large numbers of individual cells or embryos. We present the design, simulation, fabrication and characterization of (1) an off-chip-controlled microfluidic switch, (2) a high-speed microfluidic cell sorter employing thermal bubble jets, for cell and embryo sorting, and most recently (3) an acoustic stem cell sorter. [More Details...]

Localized and accurate microinjection of genetic material into biological model systems will enable a variety of studies of development biology and genetics. For such studies to be carried out in vivo, the damage caused by the injection must be minimized. We have developed surface micromachined silicon-nitride injectors with integrated force sensors for measurements of the penetration force and needle-membrane interactions under various physiological conditions. [More Details...]

Minimally invasive microsurgical tools for localized and accurate trans-membrane delivery of genetic material into cells will enable a variety of studies in biomedicine. Vibration is a well-known method for reducing the cutting force of macroscopic tools. For cellular level microsurgical tools, we report on penetration force minimization through ultrasonically actuation of silicon-nitride microinjectors. Actuated by piezoelectric actuators, the injectors are longitudinally vibrated with tip velocities controllable by actuation frequency and voltage. The forces are measured using MEMS optical-encoder force sensors integrated with the vibrating microinjectors. [More Details...]