Flow control in laser-patterned paper-based point-of-care (POC) diagnostic devices

Sones, Collin, He, Peijun, Katis, Ioannis and Eason, Robert (2017) Flow control in laser-patterned paper-based point-of-care (POC) diagnostic devices. CLEO Pacific Rim, , Singapore, Singapore. 31 Jul - 04 Aug 2017.

Abstract

In recent years, the requirements for easy-to-use, low-cost and accurate diagnostic solutions have led to a rapid progress in the research of POC diagnostic devices, especially lab-on-chip (LOC) type POC devices with origins in the 1990s [1]. Paper-based microfluidic devices, which are regarded as a low-cost alternative to conventional POC diagnostics tools, have also been popularly studied in the last decade because of the advantages they present - affordable, mass producible, disposable via incineration etc. [2] A numbers of research groups have focused onto developing fabrication methodologies, and during the past five years, several methods such as photolithography, inkjet printing, printing of wax, laser cutting etc. have already been reported [3].Although, paper is an excellent substrate wherein fluids naturally wick via capillary forces, and hence there are no requirements for external pumps to transport liquids within a paper-based device, unfortunately, the physical properties inherent with porous substrates offer limited control over fluid transport, especially with regards the flow-rate and direction of flow. This presents a critical drawback which restricts the creation of paper-based devices with complex functionalities, limiting their impact in the analytical community [3]. Therefore, research into the development of methodologies that control the flow of fluids in paper-based devices is urgently needed, and this will lead to better liquid handling and autonomous operation within the paper-based device for integrating of additional functionalities. In this report, we present our two new methodologies that allow for the control of the fluid flow in paper-based microfluidic devices: programmable flow-delay and 3 dimensional (3D) flows. Both controls are achieved using the same simple laser-based direct-write (LDW) procedure, which we have previously reported for fabrication of paper-based devices based via light-induced photo-polymerisation route [4]. Firstly, programmable flow-delay was enabled via two different fluid delay mechanisms, namely, by the formation of delay-barriers within flow paths and which are either permeable ‘delay-barriers’ with variable porosity or impermeable barriers with variable depth. Both mechanisms allow the introduction of pre-programmed or timed fluid delivery in paper-based fluidic devices. The depth or the porosity of these delay-barriers can be easily adjusted via changing the laser patterning parameters, such as the incident laser power and the writing speed. Both types of barriers yield similar results for control over the fluid flow. The resulting flow-delay was observed to depend not only on the characteristics (porosity or depth) of the delay-barriers but also on the number of barriers and the position of the barriers within the flow path. Using these delay patterning protocols we have generated flow delays which span from a few minutes to over half an hour. Secondly, the same LDW method was also extended for fabrication of 3D flow path in paper-based devices, which again allows controllable distribution of fluids, however, in both the lateral (in the paper plane) and vertical directions. In brief, by controlling the laser patterning conditions, we could produce solid hydrophobic structures either partially inside a single layer of paper or all the way through a few layers of paper. Thus by selectively patterning from both sides of the paper we could fabricate 3D flow paths within both a single layer of paper and a stack containing multiple layers of paper.
In conclusion, a number of advantages can be enabled through the implementation of these flow control methodologies, however, it further also provides an important advantage over other routes because it the same laser-patterning procedure that allows the fabrication of both the device and the flow control pathways. Additionally, in contrast to other methods reported for producing flow control in paper-based devices, our approach eliminates the requirements for cleanroom-based infrastructure, or custom-designed equipment, or even the need for proprietary materials. Above all, we believe that this integrated laser-based patterning process presents a simple route for commercial-scale manufacturing and hence could be an ideal choice for rapid fabrication of affordable, custom-designed paper-based microfluidic devices for realisation of both single-step or multi-step analytical tests.

This record has no associated files available for download.

Contributors

Author: Ioannis Katis

Author: Robert Eason

Download statistics