Suspended microchannel resonators for biomolecular detection

Abstract

Microfabricated transducers enable the label-free detection of biological molecules in nanoliter sized samples. Integrating microfluidic detect ion and sample-preparat ion can greatly leverage experimental efforts in systems biology and pharmaceutical research by increasing analysis throughput while dramatically reducing reagent cost.Microfabricated resonant mass sensors are among the most sensitive devices for chemical detection, but degradation of the sensitivity in liquid has so far hindered their successful application in biology. This thesis introduces a type of resonant transducer that overcomes this limitation by a new device design: Adsorption of molecules to the inside walls of a suspended microfluidic channel is detected by measuring the change in mechanical resonance frequency of the channel. In contrast to resonant mass sensors submersed in water, the sensitivity and frequency resolution of the suspended microchannel resonator is not degraded by the presence of the fluid. Our device differs from a vibrating tube densitometer in that the channel is very thin, and only molecules that bind to the walls can build up enough mass to be detected; this provides a path to specificity via molecular recognition by immobilized receptors.Suspended silicon nitride channels have been fabricated through a sacrificial polysilicon process and bulk micromachining, and the packaging and microfluidic interfacing of the resonant sensors has been addressed. Device characterization at 30 mTorr ambient pressure reveals a quality factor of more than 10,000 for water filled resonators; this is two orders of magnitude higher than previously demonstrated Q-values of resonant mass sensors for biological measurements.Calculation of the noise and the sensitivity of suspended microchannel resonators indi-

Low-concentration mechanical biosensor based on a photonic crystal nanowire array

“…Th e surface area-to-volume ratio of our ordered NW array resonator is extremely large (up to 10 8 m − 1 ). Th is is nearly two and three orders of magnitude larger than that of the micro-cantilever 17 and the suspended microchannel resonators 6,12 , respectively. Th is large surface area-to-volume ratio allows highly eff ective surface-based biomolecular mass sensing, especially at low target concentrations ( Fig.…”

“…3d ), the optical actuation frequency was fi xed at the resonance mode and the interferometer laser gun was controlled by a stage controller for lateral movement with sub 0.5 μ m lateral resolution. Based on the measured standing-wave 2D mapping pattern, the mode can be HS-(CH 2 ) 6 The dashed fi tting line is also added. The control experiment, using 10 pM non-matching DNA, is shown by a green square.…”

Recent Advances in Nanobiotechnology and High-Throughput Molecular Techniques for Systems Biomedicine

“…The scheme can be implemented into an ultrasensitive cantilever sensor array , with a 250 nm pitch to allow realtime monitoring of lipid bilayer formation on the cantilevers and fast microorganism detection. Burg and Manalis (2003) introduced label-free detection of bio-molecules and single cells in a micro-channel resonator which did not require the exposure of samples to vacuum, integrating a resonant cantilever and a sample-carry-ing channel in the same structure. Binding of various biomolecules or passage of a single cell shifts the resonant frequency of the cantilever to allow fast online detection.…”

Fabrication and Testing of Microfluidic Optomechanical Oscillators

“…Light is evanescently coupled into the optical whispering-gallery modes of these 'bottles' by means of a tapered optical fiber 18 . Confinement of the liquid inside 19,20 the capillary resonator, as opposed to outside it, enables high mechanical-and optical-quality factors simultaneously, which allows the optical excitation of mechanical modes by means of both RP and SBS. As has been shown, these mechanical excitations are able to penetrate into the fluid within the device 12,13 , forming a shared solid-liquid resonant mode, thus enabling an opto-mechanical interface to the fluidic environment within.…”