Optical approach for microfluidic DNA electrophoresis detection

A DNA analyzer, comprising:

• an interface for coupling a micro fluidic chip to the DNA analyzer, wherein the microfluidic chip includes:
• a first domain configured for polymerase chain reaction (PCR) amplification of DNA fragments, the DNA fragments being tagged with fluorescent labels;
• and
• a second domain fluidically coupled to the first domain to receive the DNA fragments, the second domain having a separation channel for electrophoretic separation of the DNA fragments;
• a detection module configured to be optically coupled with the microfluidic chip that includes:
• a laser source configured to generate a laser beam;
• a passive optics module including passive units that are pre-configured to receive the laser beam and transmit the laser beam;
• and
• an active optics module including at least an active unit to focus the laser beam to the separation channel to excite the fluorescent labels to emit fluorescence while the DNA fragments migrate in the separation channel, and to collect the emitted fluorescence from the separation channel into an optical signal for return, wherein:
• the passive optics module includes:
• a filter module configured to filter the optical signal to allow a first portion of the optical signal having a first wavelength to pass;
• and
• a photo-detector configured to generate an electrical detection signal in response to the filtered optical signal;
• the active optics module is configured to be calibrated with respect to each microfluidic chip and the passive optics module is configured not to be adjusted for every microfluidic chip;
• a modulation signal generator coupled to the filter module, the modulation signal generator being configured to generate a modulation signal having a modulation frequency, and a reference signal having the modulation frequency, the modulation signal being used by the filter module to modulate the filtered optical signal;
• and
• a phase-sensitive detector configured to receive the reference signal and the electrical detection signal corresponding to the modulated filtered optical signal, and demodulate the electrical detection signal based on the reference signal to remove noise due to the photo-detector.