Degassed PDMS pump for controlled extraction from dried filter samples in microfluidic devices
Simplified sample collection methods can continue to advance the field of biosensors by decreasing the cost required to acquire and store samples and/or increasing the number of locations where the sensors can be used. Filter samples have become increasingly popular as low-cost, simple methods to collect samples and are widely used for a variety of applications including dried blood spots in neonatal screening. Dried filter samples, however, limit the available sample volume and require sample extraction for analysis, increasing analysis time and cost. Combining microfluidic devices with low-cost, power-free pumps made from degassed PDMS allows for simple control over extraction time from dried filters prior to fluid transport to internal electrodes for electrochemical biomarker detection while also removing the need for traditional powered pumps. When combined with an electrochemical microfluidic device, extraction for 5 min provided an extraction efficiency of 31.8 ± 5.6% for dopamine samples dried onto filters. The reported system provides a sensitivity of 9.9 ± 0.3 nA mM−1 for dopamine as a model analyte in a simple phosphate buffer, which could be further improved by stacking filters for simultaneous extraction and improving extraction efficiency from the filters. Dopamine-spiked control serum provided a signal distinguishable from the serum background, demonstrating the capability of the system to measure biomarkers in complex matrices.