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Monolithic Integration of Multiple Porous Silicon Membranes for Lab-on-a-chip Applications

Douglas Silva de Vasconcellos 1
1 LAAS-MEMS - Équipe Microsystèmes électromécaniques
LAAS - Laboratoire d'analyse et d'architecture des systèmes
Abstract : The leading cause of mortality worldwide is due to undiagnosed treatable diseases. The underlying reason is the cost and complexity of most diagnostic processes, as they are often carried out in medical centers and require expensive and complicated equipment. To tackle this issue, the development of point-of-care technology using miniaturized and low-cost lab-on-a-chip is of great importance. The analysis of a sample includes two main steps: sample preparation (sample purification and preconcentration) and sample analysis (biosensing). Different technologies have been successfully developed to implement these steps on chip, however they are usually integrated in a hybrid fashion, where the biosensor and the sample preparation module are realized separately and then combined, which increases the device complexity and possibly its final cost. The aim of this work is to offer a generic and single technological response for on chip sample preparation and sensing by means of porous silicon elements, in the form of lateral porous silicon membranes and standard vertical porous silicon layers monolithically fabricated onto a single planar microfluidic chip. Porous silicon is a nanostructured material with interesting electrical and optical characteristics that has already been used for biosensing via reflectance-based interferometry when properly functionalized and for size/charge-based filtration. Besides, it is a strong candidate for sample concentration using ion concentration polarization due to its ion-selectivity property. However, one must be able to fabricate multiple porous silicon elements with specific morphologies (pore size and porosity) on the same chip, which has not been achieved yet, in order to use porous silicon as a generic technological brick for various functions. Porous silicon is usually fabricated through electrochemical anodization and the doping condition of silicon is one of the parameters that controls the porous layer morphology. We have thus developed a fabrication process based on the selective ion implantation of SOI substrates in order to achieve numerous porous elements of distinct characteristics using a single anodization step. We have successfully fabricated lateral porous silicon membranes bridging planar microchannels with twofold increase in pore size from non-implanted to implanted regions onto a single chip (from ~25 to ~50 nm), while the porosity varied from ~80 to ~90%. By etching the buried oxide layer, we have also formed vertical porous silicon layers, with ~35 nm pore size and ~65% porosity, at the bottom of the microchannels on the same sample. Using the developed fabrication processes, we have designed and fabricated a monolithic lab-on-a-chip integrating sample preconcentration and filtration stages, with a potential to achieve biosensing through optical interferometry.
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https://hal.laas.fr/tel-03131243
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Submitted on : Thursday, February 4, 2021 - 11:08:42 AM
Last modification on : Tuesday, February 9, 2021 - 3:29:09 AM
Long-term archiving on: : Wednesday, May 5, 2021 - 6:22:28 PM

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  • HAL Id : tel-03131243, version 1

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Douglas Silva de Vasconcellos. Monolithic Integration of Multiple Porous Silicon Membranes for Lab-on-a-chip Applications. Micro and nanotechnologies/Microelectronics. Université Toulouse 3 Paul Sabatier (UT3 Paul Sabatier), 2020. English. ⟨tel-03131243⟩

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