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A Polymer-Based Microfluidic Platform Featuring On-Chip Actuated Hydrogel Valves for Disposable Applications

present a highly functional polymer-based microfluidic device for disposable applications. This device is plastic injection molded and exhibits three levels of functionality: 1) fluidic interconnects are monolithically integrated with the device, enabling robust manufacturing and high-pressure operation (> 3.5 MPa); 2) a metal layer is lithographically patterned in the form of microheaters; and 3) a thermally sensitive hydrogel valve is integrated into the channel. The valve is normally closed at room temperature. Upon heating to above the lower critical solution temperature of 32°C, the polymer valve becomes hydrophobic, shrinks while forming large pores, and permits flow. The device has been actuated reliably over 100 times with no apparent degradation. The valve closing response using the integrated on-chip heaters is 5 s, as opposed to 20 s when using off-chip heat sources. On average, a completed device can be fabricated in less than 2 h and only requires an external pressure source and electrical controller for operation.