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In this paper, a skin-contact-actuated dispenser/micropump for transdermal drug delivery applications is presented. The micropump consists of stacked polydimethylsiloxane layers mounted on a silicon substrate and operates based on the evaporation and condensation of a low-boiling-point liquid. Therefore, there is no need for a heater and a power source, since only the thermal energy provided by skin contact is required for the actuation. A prototype device with overall dimensions of 14 mm × 14 mm × 8 mm is fabricated and characterized. For a perfluoro compound working fluid (3M FC-3284), a flow rate of 28.8 μ L/min and a maximum back pressure of 28.9 kPa is measured.

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Originally developed for use in controlled laboratory settings, potentiometric ionselective electrode (ISE) sensors have recently been deployed for continuous, in situ measurement of analyte concentration in agricultural (e.g., nitrate), environmental (e.g., ocean acidification), industrial (e.g., wastewater), and health-care sectors (e.g., sweat sensors). However, due to uncontrolled temperature and lack of frequent calibration in these field applications, it has been difficult to achieve accuracy comparable to the laboratory setting. In this paper, we propose a novel temperature self-calibration method where the ISE sensors can serve as their own thermometer and therefore precisely measure the analyte concentration in the field condition by compensating for the temperature variations. We validate the method with controlled experiments using pH and nitrate ISEs, which use the Nernst principle for electrochemical sensing. We show that, using temperature self-calibration, pH and nitrate can be measured within 0.3% and 5% of the true concentration, respectively, under varying concentrations and temperature conditions. Moreover, we perform a field study to continuously monitor the nitrate concentration of an agricultural field over a period of 6 days. Our temperature self-calibration approach determines the nitrate concentration within 4% of the ground truth measured by laboratory-based high-precision nitrate sensors. Our approach is general and would allow battery-free temperature-corrected analyte measurement for all Nernst principle-based sensors being deployed as wearable or implantable sensors.