Laser-induced selective wax reflow for paper-based microfluidics

Abstract

This study proposes a one-step method for the fabrication of paper-based microfluidics using laser-induced selective wax reflow and penetration.

Fabrication and Applications of Microfluidic Devices: A Review

“…Since 2007, paper-based microfluidics has been explored as an alternative to expensive materials for microfluidic applications [ 34 , 39 ]. Paper-based systems benefit from simplicity [ 40 ], accessibility [ 29 ], significant low costs [ 29 , 39 , 40 , 41 ], high porosity [ 2 , 29 ], high physical absorption [ 24 ], ease of manipulation and sterilization [ 29 ], potential for chemical or biological modifications [ 29 ], similarity to the native ECM [ 29 ], bio-affinity [ 24 ], biocompatibility [ 29 ], light weights [ 41 ], and the ability to operate without supporting equipment [ 39 , 41 ]. What makes paper so special is the surface tension of a fluid and its contact angle with cellulose fibers [ 33 ].…”

“…What makes paper so special is the surface tension of a fluid and its contact angle with cellulose fibers [ 33 ]. Hence, the paper’s fluid flow is influenced mostly by the cohesive and adhesive forces that produce capillary action in the cellulose matrix [ 41 , 42 , 43 ]. Some researchers treat the pressure force in the analogy with electric circuits, comparing it to the electric voltage source that pushes fluid through the network [ 33 ].…”

“…The special behavior of paper and its advantageous properties make this material suitable for a variety of applications [ 34 ]. Paper-based systems are attractive for rapid point-of-care diagnostic testing and medical screening in the developing world [ 39 , 41 , 42 ], being mostly used together with a colorimetric or an electrochemical readout for detecting target biomolecules [ 24 , 42 ]. Besides, paper microfluidic systems can be directly and in situ operated, even in the absence of technical infrastructure and trained experts, making these devices a promising solution for field analysis or testing at home [ 40 ].…”

Paper-based sensors for diagnostics, human activity monitoring, food safety and environmental detection

“…Another laser-based method involves heating paper pre-coated with hydrophobic substances so that hydrophobic substances can penetrate at high temperature to form a hydrophobic barrier. Zhang et al 77 deposited wax evenly on the paper surface, used laser heating to make wax penetrate the paper to form hydrophobic barriers and microfluidic channels, where the specific preparation process is shown in Figure 1E. Laser-techniques have also been used to remove specific areas of hydrophobic material in the paper to create hydrophobic channels.…”

Realization of Optimized Wax Laminated Microfluidic Paper-Based Analytical Devices

“…2,3 So far, several fabrication methodologies to develop μPADs have been reported which can be classified mainly into two categories. In the first category, the formation of hydrophobic (wax) barrier was directly achieved by different techniques such as photolithography, 4 soft-lithography, 5 inkjet etching and printing, [6][7][8] ink stamping, 9 plasma and laser treatment, 10,11 screen printing 12,13 and 3D printing. 14 In the second category, the μPADs have been fabricated by manual plotting and cutting and paper patterning.…”