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STMicro shows dual-function DNA analysis chip

Posted: 11 Nov 2002 ?? ?Print Version ?Bookmark and Share

Keywords:stmicroelectronics? dna analysis chip? microfluidic ic? microelectromechanical system? mems?

STMicroelectronics demonstrated a dual-function microfluidic chip that can both amplify DNA and analyze the results of the reaction. The MEMS system was created as a spin-off from inkjet print heads, which are essentially a silicon-based microfluidic technology.

Tiny samples of DNA go through a temperature cycle that doubles the amount of genetic material in the sample each time, and the results are piped into another area of the chip containing gold electrodes with specific DNA strands attached. A match is detected optically, offering a single-chip solution for bedside medical diagnostics.

"Our goal with the project was to show that it is possible to integrate two functions on the same chip," said Barbara Grieco, business development manager in ST's Printhead and Microfluidics Business Unit. The next step will be to see if even more functions can be integrated, she said. In the meantime, ST is developing a lab in Catania, Sicily, that will bring together MEMS engineers and biotechnology experts.

Already, STMicroelectronics has developed other products based on MEMS, such as a fingerprint-identification chip. "Three years ago, we developed a prototype of the DNA analysis chip with the French Atomic Commission," Grieco said. "We are looking for partners in the biotech industry, since it does not make sense for us to try to duplicate that kind of expertise."

The business model for the new lab-on-a-chip effort is similar to semiconductor manufacturing: ST will provide the chips, and experts in various biotech fields will use them to build small, low-cost portable analysis systems. The DNA analysis system is the first of its kind to reach the point of commercialization, Grieco said.

"The ability to do this in silicon is an important capability, since it requires good thermal conduction to work," she explained. Silicon is a good thermal conductor, whereas most microfluidic systems are built with plastic substrates that would not work very well with the thermal cycling, which oscillates between 20C and 60C.

A bottleneck with the polymerase chain reaction is the long time that the amplification cycle takes. The small scale of the microfluidic chip helps to reduce the time for amplification of a sample, but even with that advantage, the entire analysis process takes about an hour. In addition, the microchannels cannot be cleaned after the reaction, so the chip has to be thrown away.

An important advantage of single-chip analysis, in addition to speed and portability, is a reduction in the amount of reagents needed to complete the analysis sequence. "You only need a small volume of reagents - about 2.5?L," said Grieco.

Grieco expects the DNA analysis chip will find applications for bedside monitoring of patients and could also be used in agriculture, for monitoring livestock for genetic disease. Another possibility would be crime-scene DNA analysis. The chip measures 3cm on a side and requires 10 mask steps to fabricate on a silicon MEMS fab line.

- Chappell Brown

EE Times





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