Oriented composite nanofibers consisting of porous silicon nanoparticles (pSiNPs) embedded in a polycaprolactone or poly(lactide-co-glycolide) matrix are prepared by spray nebulization from chloroform solutions using an airbrush. The nanofibers can be oriented by an appropriate positioning of the airbrush nozzle, and they can direct growth of neurites from rat dorsal root ganglion neurons. When loaded with the model protein lysozyme, the pSiNPs allow the generation of nanofiber scaffolds that carry and deliver the protein under physiologic conditions (phosphate-buffered saline (PBS), at 37 °C) for up to 60 d, retaining 75% of the enzymatic activity over this time period. The mass loading of protein in the pSiNPs is 36%, and in the resulting polymer/pSiNP scaffolds it is 3.6%. The use of pSiNPs that display intrinsic photoluminescence (from the quantum-confined Si nanostructure) allows the polymer/pSiNP composites to be definitively identified and tracked by time-gated photoluminescence imaging. The remarkable ability of the pSiNPs to protect the protein payload from denaturation, both during processing and for the duration of the long-term aqueous release study, establishes a model for the generation of biodegradable nanofiber scaffolds that can load and deliver sensitive biologics.

The use of high‐shear microfluidization as a rapid, reproducible, and high‐yield method to prepare nanoparticles of porous silicon (pSi) with a narrow size distribution is described. Porous films prepared by electrochemical etch of a single‐crystal silicon wafer are removed from the substrate, fragmented, dispersed in an aqueous solution, and then processed with a microfluidizer, which generates high yields (57%) of pSi nanoparticles of narrow size distribution (PDI = 0.263) without a filtration step. Preparation of pSi nanoparticles via microfluidization improves yields (by 2.4‐fold) and particle size uniformity (by 1.8‐fold), and it lowers the total processing time (by 36‐fold) over standard ultrasonication or ball milling methods. The average diameter of the nanoparticles can be adjusted over the range 150–350 nm by appropriate adjustment of processing steps. If the fluid carrier in the microfluidizer contains an oxidant for Si, the resulting pSi particles are prepared with a core–shell structure, in which an elemental Si core is encased in a silicon oxide shell. When an aqueous sodium tetraborate processing solution is used, microfluidization generates photoluminescent core–shell pSi particles with a quantum yield of 19% in a single step in less than 20 min.

A porous photonic crystal is integrated with a plastic medical fixture (IV connector hub) to provide a visual colorimetric sensor to indicate the presence or absence of alcohol used to sterilize the fixture. The photonic crystal is prepared in porous silicon (pSi) by electrochemical anodization of single crystal silicon, and the porosity and the stop band of the material is engineered such that the integrated device visibly changes color (green to red or blue to green) when infiltrated with alcohol. Two types of self-reporting devices are prepared and their performance compared: the first type involves heat-assisted fusion of a freestanding pSi photonic crystal to the connector end of a preformed polycarbonate hub, forming a composite where the unfilled portion of the pSi film acts as the sensor; the second involves generation of an all-polymer replica of the pSi photonic crystal by complete thermal infiltration of the pSi film and subsequent chemical dissolution of the pSi portion. Both types of sensors visibly change color when wetted with alcohol, and the color reverts to the original upon evaporation of the liquid. The sensor performance is verified using E. coli-infected samples.