For the past two years, College of Engineering faculty members across Mechanical, Environmental, and Biomedical Engineering have been developing a device that combines the latest in micro technology, biology, fluidics and materials science to analyze disease-causing microorganisms in the environment. What began as an effort to detect potentially deadly bacteria in manufacturing lubricants has suddenly become a technology with potential as a low-cost early-warning detector of other conceivably deadly biological agents -- anthrax, for one -- that have become weapons of war. This technology, called the Micro Integrated Flow Cytometer (MIFC), has the potential to be an inexpensive addition to security measures in this new age of uncertain vulnerability.

Flow cytometers, which rapidly identify and count bacteria, cells and particles have been in clinical use for years. These instruments typically cost $150,000, require a trained technician and are roughly the size of a television. According to Steven Skerlos, assistant professor of Mechanical Engineering, "After considering manufacturing applications for microbial detectors, the need became obvious for smaller, cheaper and more user-friendly flow cytometers." Skerlos and Mechanical Engineering Assistant Professor Katsuo Kurabayashi developed the initial concept for the MIFC, which is a hand-held and high-tech analogue to conventional flow cytometers. They were soon joined by Shuichi Takayama, whose expertise lies in micro fluidics and fabrication, and Professor Peter Adriaens, an environmental microbiologist.

The MIFC research team is currently performing research that will distinguish the MIFC from conventional flow cytometers. Ultimately, the research goal of the MIFC program is to develop and integrate 11 state-of-the-art technologies to create a flow cytometer with a size and cost similar to a portable CD player. The device is designed to operate under real-world environmental conditions, as would be required for an early-warning medical or security device.

Schematic of flow-cytometry concept. The MIFC is a hand-held high-tech alternative to conventional flow cytometers.

One of the 11 technologies uses air to focus small liquid samples and produce a column of single-file microbes that is about one-fifth the width of a human hair. This technology would allow the MIFC to eliminate the use of gallons of sheath liquid. The necessity for large volumes of liquid is one of the main reasons why most cytometers are currently only used in laboratories. "Very thin columns of liquid are inherently susceptible to instabilities," said Takayama. "People think that any perturbation will break up the column." Yet research he has performed in collaboration with Professor James Grotberg of Biomedical Engineering, research assistant Dongeun Huh, and research associate Hsien-Hung Wei, has demonstrated that it is possible to achieve stable flow, making air potentially suitable for the MIFC.

Another technology that has led to the feasibility of the MIFC is the application of a process called soft lithography. This process, introduced to the group by Takayama, simplified and reduced the cost of the microfabrication process. Kurabayashi and Skerlos, along with research assistants Yi-Chung Tung and Chih-Ting Lin, are exploiting two characteristics of soft lithography - the optical transparency and moldability of materials - to integrate the optical system directly into the fluid channel structure. This integration, along with the use of air, would reduce the size of the MIFC by at least a factor of 10. The same group of researchers working on the integration of the optical system is also experimenting with new methods to improve the detection performance of inexpensive silicon-based detectors under real-world conditions. The MIFC will use these detectors to replace the large, fragile and expensive vacuum-based detectors currently found on flow cytometers.
 

Microbes under fluoresence. The MIFC has the potential to be a low-cost early-warning detector of biological agents.

This optical and electronic detection system for the MIFC will be validated using methods developed by Adriaens and co-workers Shu-Chi Chang and Anna Khijnak, who currently conduct microbial analysis using a conventional flow cytometer. Their research is developing the knowledge necessary to reduce potential interference that the MIFC might encounter while operating under potentially harsh environmental conditions. Adriaens also expects that his group will be able to determine the minimum necessary performance of the MIFC to function in real-world applications.
 

The micro-manufactured flow chamber (yellow rectangle) in the MIFC generates a high-speed stream of microbial cells and houses the optical detection system, both of which help determine the number of cells/particles detected per unit of time.

The research team is not stopping with hardware development. The team is also designing the necessary biological probes and preparation methods that the MIFC requires in order to identify microorganisms of interest in medical, ecological or manufacturing applications. Toward this end, Skerlos and Adriaens are currently researching the design and application of biological probes that would be compatible with the MIFC and would permit the identification of microorganisms based on their DNA content. The use of a DNA-based detection methodology opens up the possibility of using the MIFC to detect anthrax, as well as other biological agents that cause human health hazards, such as tuberculosis. Consequently, the successful development of the MIFC would have important applications both domestically and globally.