Suspended microchannel resonators for ultralow volume universal detection

Abstract

Universal detectors that maintain high sensitivity as the detection volume is reduced to the sub-nanoliter scale can enhance the utility of miniaturized total analysis systems ([mu]-TAS). Here the unique scaling properties of the suspended microchannel resonator (SMR) are exploited to show universal detection in a 10 pL analysis volume with a density detection limit of ~1 ([mu]g/cm³ (10 Hz bandwidth) and a linear dynamic range of six decades. Analytes with low UV extinction coefficients such as polyethylene glycol (PEG) 8 KDa, glucose, and glycine are measured with molar detection limits of 0.66 ([mu]M, 13.5 ([mu]M, and 31.6 ([mu]M, respectively. To demonstrate the potential for real-time monitoring, gel filtration chromatography was used to separate different molecular weights of PEG as the SMR acquired a chromatogram by measuring the eluate density. This work suggests that the SMR could offer a simple and sensitive universal detector for various separation systems from liquid chromatography to capillary electrophoresis. Moreover, since the SMR is itself a microfluidic channel, it can be directly integrated into ([mu]-TAS without compromising overall performance.