K. Mathwig, D. Mampallil, S. Kang and S. G. Lemay
Electrical Cross-Correlation Spectroscopy: Measuring Picoliter-per-Minute Flows in Nanochannels
Physical Review Letters 109 (2012) 118302.
→ See accompanying Focus in Physics 5 (2012) 101.
→ See also News in New Scientist 2883 (2012) 15.
We introduce all-electrical cross-correlation spectroscopy of molecular number fluctuations in nano-fluidic channels. Our approach is based on a pair of nanogap electrochemical transducers located downstream from each other in the channel. When liquid is driven through this device, mesoscopic fluctuations in the local density of molecules are transported along the channel. We perform a time-of-flight measurement of these fluctuations by cross-correlating current-time traces obtained at the two detectors. Thereby we are able to detect ultralow liquid flow rates below 10 pL/min. This method constitutes the electrical equivalent of fluorescence cross-correlation spectroscopy.