This project is a multidisciplinary effort to novelly exploit CMOS silicon microelectronics in the design of low-cost, portable, self-contained “gene chip” technology for nucleic acid measurement and detection. Much of this effort is focussed on developing active substrates based on fluorescence detection. One such active microarray is shown below, capable of time-resolved fluorescence detection for background rejection (though time-gating) and fluorescence-lifetime measurement. DNA probe is attached directly to the chip surface for detection.
This paper describes the design of an active CMOS sensor array for fluorescence applications which enables timegated, time-resolved fluorescence spectroscopy. The 64 x 64 array is sensitive to photon densities as low as 8 x 106 photons/ cm2 with 64-point averaging and, through a differential pixel design, has a measured impulse response of better than 800 ps. Applications include both active microarrays and high-frame-rate imagers for fluorescence lifetime imaging microscopy.
A 64-by-64-pixel CMOS single-photon avalanche diode (SPAD) imager for time-resolved fluorescence detection features actively quenched and reset pixels, allowing gated detection to eliminate pile-up nonlinearities common to most time-correlated single-photon counting (TCSPC) approaches. Reset Timing information is collected using an on-chip time-tocalb calibrated digital converter (TDC) based on a counter and a supply- interpolators regulated delay-locked loop (DLL).
Surface-based sensing assays based on fluorescence-based detection have become commonplace for both environmental and biomedical diagnostics. Traditional array scanners are expensive, large, and complex instruments. This paper describes the design of an active CMOS biosensor substrate for fluorescence-based assays that enables time-gated, time-resolved fluorescence spectroscopy without the need for an external reader. The array is sensitive to photon densities as low as 1 15 108 cm2, has a dynamic range of over 74 dB, and has subnanosecond timing resolution. Sensitivity is achieved through subsampling and averaging.
G. Patounakis, K. L. Shepard, and R. Levicky, “Active CMOS biochip for time-resolved fluorescence detection” Symposium on VLSI Circuits, 2005.Continue reading →