Laser-treated hydrophobic paper: an inexpensive microfluidic platform

Abstract

We report a method for fabricating inexpensive microfluidic platforms on paper using laser treatment. Any paper with a hydrophobic surface coating (e.g., parchment paper, wax paper, palette paper) can be used for this purpose. We were able to selectively modify the surface structure and property (hydrophobic to hydrophilic) of several such papers using a CO(2) laser. We created patterns down to a minimum feature size of 62±1 µm. The modified surface exhibited a highly porous structure which helped to trap/localize chemical and biological aqueous reagents for analysis. The treated surfaces were stable over time and were used to self-assemble arrays of aqueous droplets. Furthermore, we selectively deposited silica microparticles on patterned areas to allow lateral diffusion from one end of a channel to the other. Finally, we demonstrated the applicability of this platform to perform chemical reactions using luminol-based hemoglobin detection.

A perspective on paper-based microfluidics: Current status and future trends

“…However, they have not been widely used in paper-based microfluidics; only a few studies investigated using these two detection methods for detecting analytes in paper-based microfluidic devices or paper-based microarray plates. 16,19,41 Figure 5(c) shows an approach of conducting ECL detection on paper-based microfluidic devices.…”

“…19 The fundamental principle underlying these fabrication techniques is to pattern hydrophilichydrophobic contrast on a sheet of paper in order to create micron-scale (i.e., hundreds to thousands of micrometers) capillary channels on paper. The cutting technique is an exception to this methodology; it first shapes paper pattern by cutting it with a computer controlled plotter cutter and then encases the shaped paper with sticky tape, which serves as a backing to create paperbased microfluidic devices.…”

Paper-based microfluidic devices by asymmetric calendaring

“…To validate the capability of fabricated channels as microfluidic devices, a "Y" design was used for fluid flow and theoretically compared with the literature (Figures 3(a)-3(c)). 5,8,10,11,14,16,18,20,[37][38][39][40][41][42][43] Other geometries were also fabricated (Figures 3(d) and 3(e)) to show the versatility of the targeted asymmetric calendaring and hydrophobization (TACH) method. The microfluidic devices were manufactured using paper and tested with dyed water (food color) for visualization.…”

“…5,[8][9][10][11][12][13][14][15][16][17][18][19][20][21] A range of methods have been developed to control its wetting properties, such as surface modification through particle deposition, wax printing, and sol-gel techniques, among many others. 8,9,16,[22][23][24][25][26][27] Paper as a material is asymmetric in its porosity across the thickness, a feature that is a consequence of the preparation methods. The core of a paper is often significantly denser than the surfaces, allowing most of the compressive deformation to be driven by an increase in surface fiber density (decreased surface void volume) to match that of the core-as demonstrated in calendaring (Figure 1(a)).…”

Defining microchannels and valves on a hydrophobic paper by low-cost inkjet printing of aqueous or weak organic solutions

“…As a result, lPADs have emerged as a promising platform for point-of-care analytical applications in clinical diagnostics, [1][2][3] food safety control, 4,5 and environmental testing. 6,7 Various techniques have been used to fabricate lPADs, including photolithography, 8,9 wax printing, [10][11][12] inkjet printing, [13][14][15] laser etching, 16,17 plasma treatment, 18 and use of metal/paper masks. [19][20][21][22][23] Each technique has particular advantages and drawbacks.…”