Micromachined multigroove silicon ATR FT-IR internal reflection elements for chemical imaging of microfluidic devices

Abstract

The performance of low-cost, microgroove silicon (Si)-based internal reflection elements (μ-groove IREs) for infrared chemical imaging of microfluidic devices is described.

Disposable spectrofluidic devices for attenuated total reflection infrared spectroscopy: characterization sensitivity, spatial resolution and generally applicable to multiple device types

“…By integrating the peak at 3300 cm -1 of each spectrum, we obtained 2 cross-section plot profile curves which exhibited the same shape (Figure 4d). The latter behaviour was observed previously using an aperture scanning approach in the same orientation 9 and as well using a scanning synchrotron beam 7 and is related to light lost to refracted light being split into divergent paths, which are then blocked by the aperture plate on their way out. In this case, aligning channels along the ridges, can take advantage of peaks in light throughput, could be advantageous.…”

“…Independent of the detection system used previous applications of multi-ridge ATR crystals for on-chip measurements have largely relied on patterning photoresist onto the crystal sampling 4 surface to define the entire microfluidic device. 7,9,10 Thus, only the most simplistic microfluidic features could be realized on the available surface area, measuring approximately 1 cm 2 . Worse, spin-coated photoresists were dominated by edge bead effects, which resulted in non-uniform channel wall height and complicated the attachment of a sealing layer to enclose the channels.…”

“…In the sole work that was successful in sealing the channels on top of the top-side patterned device, the world-to-chip interface dominated the space requirements, leaving very little space for channels and analyte monitoring. 7 In the current work we propose a different strategy, whereby the ATR crystal is embedded into the microfluidic device. As we show, isolating the sensing to a specific region on the resulting spectrofluidic device reduces wasted sensing surface area previously used for structural support of the device.…”

Probing Heterogeneity in Attenuated Total Reflection Surface-Enhanced Infrared Absorption Spectroscopy (ATR-SEIRAS) Response with Synchrotron Infrared Microspectroscopy

“…We are currently working to improve the de-magnification factor of an imaging detector (e.g., focal plane array) installed on the horizontal ATR microscope. 43 Once these improvements are realized, the instrument will provide nearly an order of magnitude better spatial resolution. We envision that such a tool will be highly valuable in assessing heterogeneity in catalyst layers under in situ or operando electrochemical conditions.…”

“…42 We have used this beamline to chemically image H/D isotope exchange processes occurring in microfluidic devices printed directly onto a Si m-groove IREs. 43 In this study, the endstation was combined with the FcC 11 SH system in an effort to correlate the spatial distribution of the IR signal with structural heterogeneity on the electrodeposited Au@ITO layers on the Si m-groove IRE. To facilitate comparison, the exact same modified Si m-groove IRE used in the conventional spectrometer was transferred to the horizontal microscope.…”