In joint work with Paul Yager and Elain Fu in UW Bioengineering, we are using the wicking action of paper to create inexpensive and easy to use device for disease diagnostics. The devices are similar to pregnancy tests, but we use shaped paper and built-in timing mechanisms to “program” paper to carry out the steps normally done in a laboratory by a trained human or a fancy machine. Examples include automating multi-step biochemical tests such as sample preparation and signal amplification. We currently have large projects with collaborators from PATH, UW Medicine, Epoch Biosciences, and GE Global Research. Visit the link above for more information, and visit our Microfluidics 2.0 website (www.mf20.org).
Most microfluidic devices continue to rely on bulky and expensive supporting equipment, such as pumps, controllers, and detection instruments. Nearly everyone on the planet carries a device with sophisticated control and sensing functions: a cell phone. In this work we are exploiting the analogy between electrical circuits and fluidic systems to create point-of-care diagnostics controlled by the audio signals from a cell phone.
Most of my work in diagnostics focuses on design for the lowest resource settings, but many more people in the developing world can be served in the short term by modest regional laboratories with moderate equipment and training. We are working to reconfigure assay chemistries so that cumbersome and lengthy laboratory tests can be done quickly with less training and equipment.
Hydrocephalus is the inability to drain cerebrospinal fluid (CSF). It occurs in 1 in 500 live births, and if untreated normally results in death. In the 1950’s, the hydrocephalus shunt was introduced, which is a permanently implanted drainage tube and valve that drains fluid from the brain to location in the body where it can be reabsorbed (e.g., the abdomen). Shunts are life-saving devices, but they have a notorious failure rate: 40% of shunts fail by two years and 98% fail by 10 years. We are developing several technologies that aim to reduce shunt failure and provide more accurate CSF control. This work is a partnership with my friend Sam Browd, a Pediatric Neurosurgeon and UW Faculty. My contribution is applying fluidic control principles designed to address the problems that Sam faces every day.
Fluorescent probes are limited in the number that can be differentiated (multiplexed) since the colors overlap. Raman nanoparticle probes are a new class of optical labels based on surface-enhanced Raman emission that can give bright signals with unique spectral fingerprints well-suited for multiplexing. The Intel team developed composite organic inorganic nanoparticles (COINs) coupled to antibodies, and I worked on-site at the Fred Hutchinson Cancer Research Center (FHCRC) to develop COIN applications for multiplexed protein detection in cancer tissue samples. As part of this work, we developed a simple spectral fitting algorithm that is easy to implement, allows deconvolution of multiplexed Raman probe signals, allows removal of unknown background signals (e.g., tissue autofluorescence), and provides point-by-point estimates of error from multiplexed images.
When oscillating fluid is required to turn around an obstacle or a bend, it creates a secondary flow that usually involves circulating eddies. Theory was established as far back as the 19th century by Lord Rayleigh, but it has mostly been a curiosity in fluid dynamics literature. In my PhD work with Dan Schwartz, we found that this odd flow creates fluid forces that trap single cells without any physical contact. Trap forces are strong enough to hold swimming cells (we trapped swimming plankton) and to hold cells while flowing fluid past them (at very high rates). Devices are easy to build and can be driven by a home stereo amplifier. I remain interested in this area but have no current projects, but Dan has an ongoing effort (link).