Fully-Electronic DNA Sensor
Arrays on Active Silicon

The overall biochip industry will see significant growth during the next years. According to the market research company Frost & Sullivan, the total biochip market which includes microarrays, microfluids and other biochips, is expected to increase from about US$272 million to US$3.3 billion in 2006.
Today, DNA sensor arrays are usually operated using optical detection methods. In principle, electronic readout allows to avoid expensive optical set-ups and to provide more robust operation, but the status of development achieved so far is lower compared to optical platforms. The number of positions within electronic DNA chips translates into the number of sensors to be electronically addressable. In case of low-density applications (e.g. for diagnostic purposes) it is economically reasonable to fabricate only the sensors on a suitable chip substrate, and to connect all electrical terminals of these to an offchip apparatus which controls the necessary electronic signals.

This concept fails for medium (more than 100 sensor positions per chip, e.g. for pharmacogenomic purposes, HLA or viral geno-typing) and high density chips (e.g. in the field of functional genomics): The extensive number of electrical connections from each sensor position to the offchip readout setup and electrical cross-talk would result in a complete loss of signal integrity. These show stoppers can be overcome using chips with active integrated circuitry for on-chip signal-processing and signal-multiplexing: Such chips talk to the readout apparatus in terms of "robust" signals provided via a limited number of electrical connections. Besides provision of adequate high precision integrated circuitry, in this case the challenge arises to combine the required bio-compatible interface materials, sensor materials, and transducer materials with standard semiconductor production processes.

Based on its extensive expertise in all aspects related to silicon process technologies and circuit development, Infineon's aim in the biotechnology sector is to develop and manufacture semiconductor-based solutions through further development of existing semiconductor technologies. In March 2002, the company released information on its development of the world's first molecular test biochip with integrated evaluation electronics which was developed in close cooperation with the Sibanat (Silizium-Chipsystem für die biochemische Analysentechnik) project partners Eppendorf, Fraunhofer Gesellschaft IsiT, november and Siemens. In the mediumterm, the use of semiconductor-based biochip technologies will simplify, improve, make cheaper and speed up medical diagnosis. In the longterm, biochips open up new applications, such as determining whether or not a patient has adverse reactions to a medication.

Roland Thewes