Rapid flow in multilayer microfluidic paper-based analytical devices

Microfluidic paper-based analytical devices (mu PADs) are a versatile and inexpensive point-of-care (POC) technology, but their widespread adoption has been limited by slow flow rates and the inability to carry out complex in field analytical measurements. In the present work, we investigate multilayer mu PADs as a means to generate enhanced flow rates within self-pumping paper devices. Through optical and electrochemical measurements, the fluid dynamics are investigated and compared to established flow theories within mu PADs. We demonstrate a 145-fold increase in flow rate (velocity = 1.56 cm s(-1), volumetric flow rate = 1.65 mL min(-1), over 5.5 cm) through precise control of the channel height in a 2 layer paper device, as compared to archetypical 1 layer mu PAD designs. These design considerations are then applied to a selfpumping sequential injection device format, known as a three-dimensional paper network (3DPN). These 3DPN devices are characterized through flow injection analysis of a ferrocene complex and anodic stripping detection of cadmium, exhibiting a 5x enhancement in signal compared to stationary measurements.