In this project we propose to develop solar-thermal microfluidics for point-of-care diagnostics of tropical disease infections. Using this technique we believe it possible to extract and detect purified, concentrated, cholera toxin from a complex biosample, like vomit, using nothing more than creative manipulation of the ambient sunlight. A clear need exists for easy-to-use diagnostic tests that can rapidly screen complex samples, like stool or vomit, for a broad swath of bacteria and viruses associated with tropical diseases. Traditionally this has been done using simple easy to use diagnostics, such dipstick assays. These are popular because they require only the insertion of the sample and the fluid transport, sample processing, and detection reaction all occur autonomously without further input from the user or external power. While extremely successful for performing simple detection assays on simple samples (e.g. hCG in urine), when applied to the detection of rarer targets in more complex sample matrices they tend to exhibit very poor clinical sensitivity/specificity. Most of th attempts to close the gap between performance and clinical requirements have involved the incorporation of more complex microfluidics, to better process/concentrate the sample, and ultrasensitive nanobiosensors, to detect the target at lower levels. While these approaches do have better clinical performance, the added complexity, cost, and loss of autonomy stand in direct contrast with what makes the simple assays popular. Here we propose that solar-thermal microfluidics can facilitate complex sample processing in a way that is quasi-autonomous, easy to operate, and does not require any external energy input beyond ambient sunlight. Put simply, the technique involves a simple shadow mask placed between a microfluidic chip and the incident sunlight that induces a well-defined thermal pattern on the chip. We show that by creative arrangement of these thermal patterns complex sample processing operations can be achieved including: (1) thermo-phoretic sample filtration, (2) thermo-wetting triggered microfluidic transport, and (3) thermal-release following molecularly specific concentration. A user switches between different stages in the assay simply by clicking the shadow mask into a new position. Our goal in this proposal is to develop the fundamental science behind solar-thermal microfluidic sample processing and demonstrate that it can be used to extract and concentrate cholera toxin B from a synthetic vomit sample.