Frequency mixing and synchronous demodulation of dynamic chemical signals with switched-flow microfluidic chips

We demonstrate a microfluidic system for dynamic chemical signal discrimination using a spectral separation technique based on nonlinear frequency mixing and synchronous demodulation. By interrupting the input flow with a set valves pulsed at a specific frequency, the synchronous demodulator generates an output containing mostly the spectral component of the input chemical signal at the demodulation frequency. Testing demodulator chips have been fabricated using a two-level PDMS process to show the applicability of this concept. By utilizing a series of such demodulators, one could further separate the input signal spectra into its frequency domain components.