Microfluidic paper-based analytical devices or microPADs are a simple and inexpensive alternative to conventional microfluidic devices that have been developed as a platform for point-of-care diagnostic devices for use in resource-limited settings. MicroPADs traditionally rely on capillary action to distribute fluids throughout a network of hydrophilic channels patterned in paper. We have recently investigated evaporation-driven capillary flow (EDCF) as an alternative means for distributing fluids in microPADs, where fluid is pumped from a sample reservoir to an evaporation zone. A challenge associated with relying on EDCF in the field is that the rate of evaporation is affected by the temperature and humidity of the environment. We explored a method of controlling EDCF by using resistive heaters directly attached behind each evaporation zone to manipulate the temperature. The rate of EDCF increases as the temperature of the evaporation zone is increased, and we found that the rate of evaporation can be adjusted to account for variations in temperature and humidity of the environment. Using heated evaporations zones could prove useful for performing time-sensitive assays in the field where environmental conditions cannot be easily controlled.

Controlling evaporation-driven capillary flow in paper-based devices using heat

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