Optofluidic integration for microanalysis

Abstract

This review describes recent research in the application of optical techniques to microfluidic systems for chemical and biochemical analysis. The ''lab-on-achip'' presents great benefits in terms of reagent and sample consumption, speed, precision, and automation of analysis, and thus cost and ease of use, resulting in rapidly escalating adoption of microfluidic approaches. The use of light for detection of particles and chemical species within these systems is widespread because of the sensitivity and specificity which can be achieved, and optical trapping, manipulation and sorting of particles show significant benefits in terms of discrimination and reconfigurability. Nonetheless, the full integration of optical functions within microfluidic chips is in its infancy, and this review aims to highlight approaches, which may contribute to further miniaturisation and integration.

Femtosecond laser microstructuring: an enabling tool for optofluidic lab‐on‐chips

“…Several efforts have been performed in order to fabricate on-chip micro-optical components to perform optical detection [14][15][16]. The most widely used components are optical waveguides, which allow to confine and transport light in the chip directing it to a small volume of the microfluidic channel and collecting the transmitted/emitted light.…”

“…Depending on the substrate of choice, different methods can be used. Approaches reported in the literature include waveguide fabrication by silica on silicon [14][15][16][17], ion exchange in soda-lime glasses [18,19], photolithography in polymers [20,21] and liquid-core waveguides [22][23][24][25]. All these methods suffer, when applied to LOCs, from several limitations: (i) they are inherently planar techniques, i. e. they are able to define optical guiding structures only in two dimensions, close to the sample surface; (ii) they are multistep methods, involving multiple masking with critical alignments; (iii) they require cleanroom environment, and (iv) they typically create uneven surfaces which make sealing of the microfluidic channels problematic.…”

Laser microfluidics: fluid actuation by light

“…These experimental results bring us back to the Glückstad concept of "optical chip" [25], where flows, channels and operating functions on microdroplets would all be performed optically on the same device, extending by the way the optofluidic approach [16,17] to digital microfluidics.…”

“…As a preliminary conclusion, the present survey illustrates another step in the exploration of the coupling between optics and microfluidics. Associated to much more exhaustive reviews [16,17,18] and to the increasing number of publications in this domain, it illustrates the emergence of a new and very active research field. In fact, the development of optofluidics, and in our case optohydrodynamics, is obviously in its infancy, probably because it intimately mixes disciplines which have been considered far away for a long time.…”

“…Parallel actuation was also demonstrated [15]. Moreover, the combination of optics and microfluidics, called optofluidics [16,17,18], also became an emergent research field offering an unprecedented level of integration for building a new generation of optically-actuated microdevices merging optical reconfigurability, softness of fluid, smoothness of fluid interfaces, and compactness. Along this line, great achievements were realized in optical switching [19] and splitting [20], adaptive lensing [21,22], interferometry [23], and lasing [24].…”