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MicroAnalytical Systems (µAS) adapted to Point-of-Care Testing are expected to provide simple chemical, molecular or cellular analysis to be used directly on the field. Different formats of µAS are already classically used, from pregnancy tests to glycemia for diabetic people. Increasing µAS analytical performances involves for instance improving limits of detection, reduce time of analysis, or increase the amount of information provided per test. These improvements may be reached by using more refined technology, involving integrated technologies such as biosample processing, enzymatic reactions, fluidic circuitry and/or biosensors. However being able to fabricate and produce cheap µAS relying on miniaturized components is still a challenging goal, particularly when dealing with low concentrated species. For example, on the one hand it may be interesting to use miniaturize nanotransducers in biosensors (e.g. photonic transducer enabling both SPR and SERS thanks to nanostructuration) ; but on the other hand the transducers size reduction may prevent the targets to reach the biosensor’s active zone in a short time, because of mass transfer phenomena. Futhermore, when the sensing area is small by comparison with the other µAS zones, it targets are likely to get adsorbed on undesired surfaces. These targets are therefore lost and cannot contribute to the final, useful signal of the µAS. In these conditions the effectivity of the µAS can be questionned.
Different ways are being explored to overcome such challenges, and may enable µAS for detection of low concentration targets. For instance, it is possible to perform selective chemical modifications of surfaces bearing different materials, in order to bind molecular probes only on the transducing zone, while repelling molecular targets from other material surfaces. We will show how it is possible to perform such orthogonal surfaces modifications with a submicronic spatial resolution, relying on self-assembly phenomena.
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