eDNA (Click for larger image)

The eDNA project was a collabrative effort between the Plaxco Chemistry Group and the Lubin expermental Astrophysics to make a low noise potentiastat.  The purpose of the project was to design a fast, low noise multi channel poteniastat, using an FPGA to read multiple channels simultaneously and perform digital signal processing (DSP) on the board.  Previous to this the Chemistry department used a multiplexing potentiastat to read multiple channels. 

The application for the board was both general electro-chemistry and the eventual compression into a hand held device for multi target aptamer bio sensing.  The eventual goal was to have close to one hundred targets on a single test chip, to allow for testing of various biological substances.  Aptamers were successful in testing for DNA fragments, large and some small molecules; H1N1 bird flu DNA fragments, various proteins and Cocaine were all detected.  The cocaine sensor was able to react quickly to concentration and could detect the change in concentration over the course of a few minutes.

eDNA Analog Front End

To get a low noise, a large linear power supply was used, which made the device table bound.  The eventual use of a battery was planned however this was not implemented in the latest version.  The speed was about four times faster than that of the multiplexing potentiastat and read the channels simultaneously.  The data was processed in the FPGA, using logical phase sensitive demodulators, called lock-ins.  The processed data was structured and passed to a computer program where it could be visualized.  The system unfortunately was wired with specific voltage and current specifications and was not easy to change for varying sized electrodes.   A further design that would implement an auto ranging system, was proposed but never implemented.  After this, the project ended and the Chemistry department found an off the shelf device to meet their needs.

FPGA Board