UC San Diego

Advancements in the field of optical sensors have resulted in an innovative class of microoptical sensors exhibiting detection capability comparable to those sophisticated analytical laboratory instrumentations. An emerging trend is to integrate these optical sensors/detecting methods into analytical tools with the ability to perform multifunctional tasks (i.e sample filtration, detection, and signal processing etc.) all in one platform. Porous silicon possesses many fascinating features making it an attractive candidate as a spectrally encoded material that is suitable as an identifier/barcode for multi-analyte bioassays and a spatially controlled structure that is applicable as a chromatography matrix for biomolecule separation. Its high surface to volume ratio and readily tailored surface chemistry also provide additional control for enhancing selectivity. Combining its optical and physical properties together with tailored surface moieties, porous silicon material can be treated as a multifunctional material allowing simultaneous separation and detection, capable of the multiplexed, low-level biodetection necessary to accommodate complex biological mixtures such as urine, whole blood, or serum used for disease diagnosis. This thesis begins with an overview on current separation techniques and progress in the field of optical sensors and nanomaterials. The second half of the introduction discusses recent development in porous silicon material with the focus on biosensing and molecular filtration applications. The objective of this thesis is to explore porous silicon as a multifunctional material with the ability to separate, process, and detect biomolecules at low concentration and in real-time with minimal sample preparation. Interrogation of porous silicon material as a multifunctional nanostructure involved three major aspects: 1) manipulation of its optical and spectral information for encoding and signal processing applications, 2) examination of the effect of its physical properties on molecular transport within its porous structure, 3) investigation of analyte-pore surface interaction for enhanced selectivity or better separation based on analyte surface moieties. The last chapter of this thesis provides an example of exploiting porous silicon as a multifunctional matrix that is capable of capturing and concentrating analyte while processing the signal, providing a new strategy for bioanalytics