Understanding Wax Printing: A Simple Micropatterning Process for Paper-Based Microfluidics

Abstract

This technical note describes a detailed study on wax printing, a simple and inexpensive method for fabricating microfluidic devices in paper using a commercially available printer and hot plate. The printer prints patterns of solid wax on the surface of the paper, and the hot plate melts the wax so that it penetrates the full thickness of the paper. This process creates complete hydrophobic barriers in paper that define hydrophilic channels, fluid reservoirs, and reaction zones. The design of each device was based on a simple equation that accounts for the spreading of molten wax in paper.

Rapid fabrication of pressure-driven open-channel microfluidic devices in omniphobic RF paper

“…21 The cost of the materials used for functionalization with a long fluoroalkyl trichlorosilane is ~$0.80 per m 2 of paper (for reagents purchased in small quantities), slightly less than rendering paper hydrophobic by wax printing ($1 per m 2 ). 2 The 35 silanization treatment does not degrade the physical properties of the paper, and does not require pre-or post-treatment steps (e.g. washing to remove reagents or side products, drying, etc.).…”

Paper-based microfluidic devices by asymmetric calendaring

“…We demonstrated that one can easily exploit the stack ability of paper to tune (adjust) the depth of created channels (Figure 3(e)). We exploit the stackability of paper, as previously shown 5,9 to demonstrate that when multiple papers are stacked, the depth, and hence flow properties, of the channels can be tuned. This property has been widely used in microfluidic devices and we demonstrate that it is not lost with TACH.…”

“…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)).…”

Millimeter-scale contact printing of aqueous solutions using a stamp made out of paper and tape

“…At least one factor-the areas being wet-is under our control. By using wax printing 16 to define printed, hydrophilic areas of approximately 1 mm 2 in the substrate receiving transferred ink, we reduced the coefficient of variation for the measured areas from 40% ( Figure 2B) to 21% (Figure 3B), which corresponds to a reduction in the coefficient of variation from 18% to 11% for the calculated diameters. For substrates with larger printed areas of approximately 3 mm 2 and contact times of 10 s to transfer the ink from the paper-based stamp, we further reduced the coefficient of variation for the measured areas to 11% (6% for the calculated diameters).…”