A fast, reconfigurable flow switch for paper microfluidics based on selective wetting of folded paper actuator strips

Abstract

In paper microfluidics, the development of smart and versatile switches is critical for the regulation of fluid flow across multiple channels. Past approaches in creating switches are limited by long response times, large actuation fluid volumes, and use of external control circuitry. We seek to mitigate these difficulties through the development of a unique actuator device made entirely out of chromatography paper and incorporated with folds. Selective wetting of the fold with an actuation fluid, either at the crest or trough, serves to raise or lower the actuator's tip and thus engage or break the fluidic contact between channels. Here the actuator's response time is dramatically reduced (within two seconds from wetting) and a very small volume of actuation fluid is consumed (four microliters). Using this actuation principle, we implement six switch configurations which can be grouped as single-pole single-throw (normally OFF and normally ON) and single-pole double-throw (with single and double break). By employing six actuators in parallel, an autonomous colorimetric assay is built to detect the presence of three analytes - glucose, protein, and nitrite - in artificial saliva. Finally, this work brings the concept of origami to paper microfluidics where multiple-fold geometries can be exploited for programmable switching of fluidic connections.

Recent advances in lab-on-a-chip technologies for viral diagnosis

“…Another technique was employed to form superhydrophobic properties using polyhydroxybutyrate (Obeso et al, 2013). Those methods are utilized to fabricate single layer paper devices, also allowed to form 3D devices by stacking papers such as origami (Liu and Crooks, 2011), even in easily reconfigurable configuration (Kong et al, 2017). Those methods are utilized to fabricate single layer paper devices, also allowed to form 3D devices by stacking papers such as origami (Liu and Crooks, 2011), even in easily reconfigurable configuration (Kong et al, 2017).…”

Recent Advances of Fluid Manipulation Technologies in Microfluidic Paper-Based Analytical Devices (μPADs) toward Multi-Step Assays

“…Fluid manipulation methods using mechanical movement include expandable materials, magnetic valves, pressure valves, and reconfigurable flow switches, and their examples are given in Table 5. Colorimetric-enzymatic assay (glucose, protein, and nitrite) [107] Research has been conducted to control the flow of fluid using expandable material (sponge) [104]. When the sponge gets wet with the fluid flowing through the actuation channel, it expands so that the channel associated with the sponge transfers the flow of fluid to another channel or stops the flow.…”

“…The feature of this technology is that the valve can be operated repeatedly, and it is programmable and reversible. In addition to the above-mentioned techniques, research on the flow switch using the reconfigurable property of paper has been conducted [107]. The reconfigurable flow switch is a valve that uses the property of unfolding when liquid is injected into the folded part of the paper.…”

“…When the liquid is injected into the crest of the actuator made by folding the paper, it spreads out as it was before. It connects the input and output channels initially separated from each other.Figure reprintedwith permission from[107].…”

Multifunctional Soft Actuators Based on Anisotropic Paper/Polymer Bilayer Toward Bioinspired Applications

“…Paper, mainly composed of the hydrophilic cellulose fiber network, is the most accessible material and owns the advantages of low‐cost, lightweight, flexible, and biodegradable . Because of these, it has been widely investigated in many research fields such as microfluidics, flexible printed electronics, low‐cost biomedical detection, wearable sensing, and origami robots . Recently, paper is also employed as the promising candidate material for the fabrication of electrical or optical actuators which show large and reversible deformation .…”