Professor of Electrical Engineering & Materials Science
Ph.D., Massachusetts Institute of Technology, 1970
Key Words:
µTAS and MEMS, Biological Dielectrophoresis, Industrial Electrostatic
Hazards and Nuisances
Research Interests:
MEMS (MicroElectroMechanical Systems) and microTAS (micro Total Analysis
Systems) have vast potential for commercial application. MEMS technology
promises smart sensors and actuators with broad application in mechatronic
and robotic systems to complement the computational power of modern microprocessors.
The technology of microTAS leads to the so-called “Laboratory on
a Chip”, i.e., tiny bio- or chemical reactors constructed on a substrate
and capable of conducting reactions, tests, etc., automatically using
very small liquid inventories.
DEP Microfluidics
We are investigating liquid DEP (dielectrophoresis) to achieve programmable,
high-speed actuation of nanoliter liquid volumes using non-uniform, RF
electric fields created by simple, co-planar electrode structures. We
have used DEP liquid actuation to achieve transient flow velocities up
to ~25 cm/sec and multiple nanoliter droplet formation in ~30 milliseconds.
MicroDEP may find application as a microfluidic interface to distribute
and dispense liquids in chip-level processors and reactors.
Micromechanical Systems
Higher-order vibrational modes of beams and other mechanical resonators
show improved vibration isolation and reduced susceptibility to attachment
conditions, a property that should be lead to more robust MEMS designs.
Better vibration isolation may reduce the susceptibility of MEMS elements
to fatigue, mechanical shock-induced failure, and in-use stiction. In
addition, higher-order modes can be exploited to create sensors that use
common-mode signal rejection for noise suppression.
Biological Dielectrophoresis
Using non-uniform, AC electric fields created by microelectrodes to collect,
probe, and process bio-particles such as cells and DNA has become an important
methodology in biotechnology. The use of microstructures created a need
for better models to estimate the electrical forces and torques. We have
developed a general multipolar model for these forces and torques and
used it to explain certain particle levitation configurations, travelling
wave structures, and electrorotational schemes.
Other Areas of Research Activity
The abatement of electrostatic hazards and nuisances associated with handling
liquids, sheet materials, and powders, is an important issue in the petroleum,
pharmaceuticals, and polymer industries. Electrostatic discharges can
cause disruptive instrumentation failures, to say nothing of dust or vapor
explosions. Over the years, we have investigated a wide range of industrial
electrostatics problems: most recently, dielectric testing procedures
to locate defects in glass-lined reaction vessels.
