Congratulations to Huijin ‘Ginny’ An in the Weiss group! Ginny’s article “Porous Silicon on Paper: A Platform for Quantitative Rapid Diagnostic Tests” has been selected as a VINSE spotlight publication.
Porous silicon (PSi) is a versatile nanophotonic material widely utilized in label-free biosensing due to its high surface area and sensitive optical properties. As an integral component of optical transducers, PSi membranes typically rely on the diffusion-limited transport of analytes into their nanoporous structure, a process that often hinders rapid and sensitive detection in traditional “flow-over” configurations. While various microfluidic integrations have attempted to address these mass transport limitations, the requirement for external pumping systems often compromises the portability and cost-effectiveness essential for point-of-care (POC) applications.
In this study, we developed a hybrid “Porous Silicon-on-Paper” platform to examine how the integration of a capillary-driven substrate enhances the delivery of analytes to the sensing functional surface. By laminating an open-ended PSi membrane onto a filter paper substrate, we created a pump-free, flow-through system that mimics the autonomous fluid handling of lateral flow assays while maintaining the high-resolution optical signaling of silicon nanostructures. Our study demonstrates that the paper-induced capillary force drives a vertical flow through the PSi nanopores, resulting in a four-fold increase in the optical response compared to traditional substrate-bound PSi sensors. These data support the potential of this hybrid architecture to bridge the gap between sophisticated laboratory-grade optical biosensors and simple, quantitative rapid diagnostic tests (RDTs) for decentralized healthcare settings.
Authors: Huijin An, Simon J. Ward, Rabeb Layouni, Paul E. Laibinis, Andrea K. Locke, and Sharon M. Weiss
Abstract: Porous silicon (PSi) thin films on silicon substrates have been extensively investigated in the context of biosensing applications, particularly for achieving label-free optical detection of a wide range of analytes. However, mass transport challenges have made it difficult for these biosensors to achieve rapid response times and low detection limits. In this work, we introduce an approach for improving the efficiency of molecule transport in PSi by using open-ended PSi membranes atop paper substrates in a flow-through sensor scheme. The paper substrate provides structural support as well as an efficient means of draining solutions from the PSi membrane without the use of an external pump and microfluidic channels. Distinct changes in the reflectance properties of the PSi membrane are measured when molecules are captured in the membrane. A concentration dependent response of the sensor for protein detection is demonstrated. Factors influencing the interaction time of molecules in the PSi membrane and the drying time of the membrane, which directly affect the detection sensitivity and overall testing time, are discussed. The demonstrated performance of the PSi-on-paper sensor establishes the feasibility of a platform for low-cost rapid diagnostic tests with a highly sensitive, quantitative readout.