Fast reconfigurable paper switch for chemical sensing applications

A method to create smart and flexible switches for the regulation of liquid flow across multiple channels is essential in paper microfluidics. Prior approaches are hampered by long response times, high actuation fluid volumes, and external control circuitry. To diminish these problems, we designed a distinctive actuator device fashioned entirely from chromatography paper and featuring folds. The fold can be selectively wetted by an actuation fluid at either the crest or trough, resulting in the raising or lowering of the actuator's tip and thus bringing about the connection or severance of fluidic channels. This actuation principle reduces the response time to only two seconds and the amount of fluid used to merely four microliters. We have also added six switch arrangements which can be divided into single-pole single-throw (normally OFF and normally ON) and single-pole double-throw (with single and double break). The utilization of six actuators in a parallel system allowed us to construct an autonomous colorimetric assay for the detection of three analytes - glucose, protein, and nitrite - in artificial saliva. This study has brought the concept of origami to paper microfluidics, allowing the use of multiple-fold geometries for the programmable switching of fluidic connections.