Breath analysis system based on phase-shifting interferometric microscopy readout of microcantilever arrays

Abstract

Microcantilever (MC) sensors can provide ultrasensitive bio-chemical detection. Monitoring the bending response of large arrays of MC sensors coated with a library of receptors will produce a characteristic 'breath-print' corresponding to the breath composition; this promises to be suitable for non-invasive medical diagnostics. While MC arrays with hundreds of individual sensors can be produced readily, conventional MC readout methods are not suitable for the parallel readout of tens or hundreds of individual sensors. We have developed a MC sensor-array readout method based on phase-shifting interferometric microscopy (PSIM) which allows for the simultaneous monitoring of the response of all MCs within the field of view of the readout microscope optics. Based on this sensor technology, we have built an exhaled breath-analysis research instrument for the Point of Care Diagnostics Development Unit at the University of Leicester, UK. In this paper, we describe the PSIM readout system and the breath-analysis instrument that will be used to test sensor surface coatings and develop sensor sets with response patterns suitable for clear correlation to patients' health condition.

Nanomechanical gas sensing with nonlinear resonant cantilevers

“…The compressive stress, together with the added mass, also gives rise to a change of the resonance frequency. This dynamic-mode response is shown in figure 1 , within the typical range for resonant gas sensors [1,6,7]. We find a different rate for the static-and dynamic-mode response, with…”

“…Sensitive techniques are available to detect these changes, which often involve a measurement of the cantilever's resonance frequency. Cantilever sensors are deployed in a variety of applications including environmental monitoring, exhaled breath analysis, point-of-care diagnostics, and biosensing, several of which have been commercialized [1][2][3][4][5][6][7][8][9][10][11].…”

Fabrication of nanoelectromechanical systems via the integration of high surface area glancing angle deposition thin films

“…(b) The cantilever deflections were plotted versus their length squared in order to find the slope of the linear fit ( ). This slope (--) was then used to calculate the surface stress using (10). The two points labeled 'stictioned' were excluded from the fit, as their extreme deflections indicated the beams were stictioned.…”

“…The remaining data were fit using linear regression. The slope of the fit was used to calculate σ s using (10). The result was σ s = 1.34±0.09 N m −1 .…”

“…High S gravimetric NEMS should have a reduced LOD, and thus significant potential for ultrasensitive mass detection in a gaseous environment. We anticipate the use of these devices in applications such as ultrasensitive gas chromatography [5], and cantilever-based breath analysis for point-of-care diagnostics [10].…”