Three-dimensional electrodes that are controllable over multiple lengthscales are very important for use in bioanalytical systems that integrate solid-phase devices with solution-phase samples. Here we present a fabrication method based on all-solution-processing and thin film wrinkling using smart polymers that is ideal for rapid prototyping of tunable three-dimensional electrodes and is extendable to large volume manufacturing. Although all-solution-processing is an attractive alternative to vapor-based techniques for low-cost manufacturing of electrodes, it often results in films suffering from low conductivity and poor substrate adhesion. These limitations are addressed here by using a smart polymer to create a conformal layer of overlapping wrinkles on the substrate to shorten the current path and embed the conductor onto the polymer layer. The structural evolution of these wrinkled electrodes, deposited by electroless deposition onto a nanoparticle seed layer, is studied at varying deposition times to understand its effects on structural parameters such as porosity, wrinkle wavelength and height. Furthermore, the effect of structural parameters on functional properties such as electro-active surface area and surface-enhanced Raman scattering is investigated. It is found that wrinkling of electroless-deposited thin films can be used to reduce sheet resistance, increase surface area, and enhance the surface-enhanced Raman scattering signal.

Urine testing is a powerful clinical diagnostic tool. The noninvasive collection of samples and wide range of diagnostic targets found in urine makes urinalysis well suited for point-of-care (PoC) monitoring applications. Complete urinalysis testing faces many limitations due to the large quantity of samples processed, the time required for testing, and the labor involved in sample preparation and processing. Development of PoC urinalysis devices with microfluidic technology can enable the detection of infections and monitoring of chronic disease while reducing the demand on testing facilities. In this article, current approaches in clinical urinalysis are reviewed. Emerging sensing and imaging technologies specifically suitable for point-of-care examination of urine samples are discussed with an outlook on the future of point of care urinalysis devices as well as emerging applications enabled by these technologies such as in situ monitoring of Activities of Daily Living (ADL).

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We report the development of a three-dimensional optical model to predict the propagation of light through multilayer optical fluorescence sensors employing total internal reflection. The ray-tracing-based model visualizes the propagation of light from a light source through the optical sensor allowing optimization of the optical path, optical properties of the materials, and the coupling strategy. The model demonstrates how light can be guided through different layers of the sensor structure by controlling the incident angle of light and the relationship between the incident angle and the relative sensitivity. Simulation results are compared against experimental data to validate the model in a fluorescence-based dissolved oxygen sensor. Customization of the light source parameters, coupling optics, sensor optical properties, and sensor dimensions could allow developers to refine and optimize sensor prototypes before conducting bench testing.