Elizabeth A. Strychalski

We are developing novel microfluidic devices for biological applications. Specifically, we are using microfluidic technology to examine anticoagulated whole blood and its components. Channels are cast in polydimethylsiloxane (PDMS) using well-known fabrication methods. The inner surfaces of the devices are chemically modified with covalently bound surface treatments to improve biocompatibility. Devices require inexpensive and uncomplicated clean room fabrication. Rapid assembly removes the need to clean channels for reuse: a new device can be used for each experiment, eliminating cross-contamination between runs. Device disposability is another feature of our chips that is desirable for clinical use as a biomedical diagnostic device.

Microfluidic devices have been constructed from glass and PDMS using well-known PDMS casting and bonding techniques. Microchannels cast in PDMS are irreversibly bonded to PDMS spun onto glass cover slides using an oxygen plasma. Polymer tubing is inserted into the side of the device in plane with the channel, or an open plastic tube is inserted perpendicular to the channel to allow pressure drive of fluid through the channel. Depending upon the specific application, a device may be modified with a surface treatment, such as polyethylene glycol. The materials, device structure, and pressure drive systems used are designed to maximize biocompatibility.

Devices are mounted on an inverted fluorescence microscope to visualize flow. Samples are driven through devices using pressure, which is typically provided by a syringe pump or hydrostatic pressure from a column of liquid. Samples for interrogation are often incubated with fluorescent labels to identify biological components of interest and characterize their flow behavior through the channels.

Biomedical diagnostic devices using microfluidic technology for the examination of whole blood and its components would improve upon conventional techniques for blood analysis and take advantage of the flow characteristics of blood through micrometer-sized channels and apertures. Conventional blood testing can require tens of milliliters of whole blood, while miniaturized testing using microfluidic geometries call for as little as a few microliters. Using point of care microfluidic diagnostic devices to examine single cells in addition to populations of cells, without the need for expensive and time-consuming sample preparation and equipment, would allow more frequent testing of more patients. The small size of microfluidic chips and their inexpensive fabrication in PDMS would give a disposable device for blood analysis at a dramatically reduced cost and improved reproducibility over conventional testing techniques.

Figure 1: Glass-capped PDMS microfluidic device assembled and ready for biological applications (Euro coin shown for scale).