Laminated and infused Parafilm® – paper for paper-based analytical devices

Abstract

Numerous fabrication methods have been reported for microfluidic paper-based analytical devices (μPADs) using barrier materials ranging from photoresist to wax. While these methods have been used with wide success, consistently producing small, high-resolution features using materials and methods that are compatible with solvents and surfactants remains a challenge. Two new methods are presented here for generating μPADs with well-defined, high-resolution structures compatible with solvents and surfactant-containing solutions by partially or fully fusing paper with Parafilm® followed by cutting with a CO laser cutter. Partial fusion leads to laminated paper (-paper) while the complete fusion results in infused paper (-paper). Patterned structures in -paper were fabricated by selective removal of the paper but not the underlying Parafilm® using a benchtop CO laser. Under optimized conditions, a gap as small as 137 ± 22 μm could be generated. Using this approach, a miniaturized paper 384-zone plate, consisting of circular detection elements with a diameter of 1.86 mm, was fabricated in 64 × 43 mm area. Furthermore, these ablation-patterned substrates were confirmed to be compatible with surfactant solutions and common organic solvents (methanol, acetonitrile and dimethylformamide), which has been achieved by very few μPAD patterning techniques. Patterns in -paper were created by completely cutting out zones of the-paper and then fixing pre-cut paper into these openings similar to the strategy of fitting a jigsaw piece into a puzzle. Upon heating, unmodified paper was readily sealed into these openings due to partial reflow of the paraffin into the paper. This unique and simple bonding method was illustrated by two types of 3D μPADs, a push-on valve and a time-gated flow distributor, without adding adhesive layers. The free-standing jigsaw-patterned sheets showed good structural stability and solution compatibility, which provided a facile alternative method for fabricating complicated μPADs.

Paper-Based Sensors: Emerging Themes and Applications

“…The device was able to detect glucose in 12 min. Kim et al introduced two methods in production of μPADs by slightly or completely infusing parafilm to the device, in which resulted in laminated paper (slightly infused) or infused paper (completely infused) [ 53 ]. Thermally pressing parafilm into the paper caused it to bond together.…”

Low cost fabrication of microfluidic paper-based analytical devices with water-based polyurethane acrylate and their application for bacterial detection

“…Since the first report from Whitesides group patterned chromatography paper using photolithography [19,20], a series of methods have been proposed for fabrication of μPADs by partially hydrophobizing the filter paper, including wax printing and dipping [21][22][23][24], inkjet printing [25], screen printing [26], vapor phase deposition [27], plasma treatment [28,29], laser cutting [30,31] and hand drawing [32]. Although more and more materials and technologies for fabrication of μPADs have developed, each has its own advantages and limitations.…”

A Flexible Method for Nanofiber-based 3D Microfluidic Device Fabrication for Water Quality Monitoring

“…The electric field, collection distance, and speed of movement could be adjusted to obtain nanofiber mats of arbitrary thickness, different pores, and multiple materials [24]. It exhibits good flexibility in terms of chemical reaction time control [25,26], and fluid velocity control [27]. Compared with paper-based microfluidic devices, the fabrication of three-dimensional nanofiber-based microfluidic analysis devices (3D-µNMADs) involves the electrospinning of nanofibers in a layer-by-layer stack and electrostatic direct writing of hydrophobic barriers.…”