Flexible microfluidic cloth-based analytical devices using a low-cost waxpatterning technique

Abstract

This paper describes the fabrication of microfluidic cloth-based analytical devices (μCADs) using a simple wax patterning method on cotton cloth for performing colorimetric bioassays. Commercial cotton cloth fabric is proposed as a new inexpensive, lightweight, and flexible platform for fabricating two- (2D) and three-dimensional (3D) microfluidic systems. We demonstrated that the wicking property of the cotton microfluidic channel can be improved by scouring in soda ash (Na(2)CO(3)) solution which will remove the natural surface wax and expose the underlying texture of the cellulose fiber. After this treatment, we fabricated narrow hydrophilic channels with hydrophobic barriers made from patterned wax to define the 2D microfluidic devices. The designed pattern is carved on wax-impregnated paper, and subsequently transferred to attached cotton cloth by heat treatment. To further obtain 3D microfluidic devices having multiple layers of pattern, a single layer of wax patterned cloth can be folded along a predefined folding line and subsequently pressed using mechanical force. All the fabrication steps are simple and low cost since no special equipment is required. Diagnostic application of cloth-based devices is shown by the development of simple devices that wick and distribute microvolumes of simulated body fluids along the hydrophilic channels into reaction zones to react with analytical reagents. Colorimetric detection of bovine serum albumin (BSA) in artificial urine is carried out by direct visual observation of bromophenol blue (BPB) colour change in the reaction zones. Finally, we show the flexibility of the novel microfluidic platform by conducting a similar reaction in a bent pinned μCAD.

Exploration of microfluidic devices based on multi-filament threads and textiles: A review

“…Nilghaz et al fabricated 3-D microfluidic cloth-based devices (lCADs) with confined detection zones by restricting flow within the cotton fabric to microfluidic channels formed through the deposition of hydrophobic wax. 8 Although lCADs created by Nilghaz et al have similarities to lPADs, they retain the flexibility and mechanical strength of fabrics. As shown in Fig.…”

“…3, this approach has advantages such as having specific detection zones as well as being more compact and embeddable for 3-D devices. 8,27,28 They fabricated 2-D microfluidic channels on a single layer of cloth using hydrophobic wax resist. This structure conveyed liquid within the hydrophilic channels, allowing the fabrication of distinct detection zones which could be functionalized with colorimetric reagents.…”

“…However, they have enhanced the wettability of the cotton cloth by performing a scouring treatment using Na 2 CO 3 hot bath which was both safer and more error-tolerant in comparison with NaOH scouring (mercerization). 8 The procedure included boiling the cloth in dilute Na 2 CO 3 solution before washing with an ample amount of water to remove any remaining Na 2 CO 3 . Then, the scoured and un-scoured cotton cloths were characterized by XPS which indicated that wax in natural cotton fibres was removed from the fibre surface after treatment.…”

“…[4][5][6][7][8][9][10][11] Although the porous fibre structures in threads provide capillary channels, some natural fibres are coated waxes composed of long fatty acid chains; the natural plant wax reduces or even stops the liquid wicking within threads. 4,6,8,12 Wettability of these fibres can be enhanced by removing the natural waxes from the fibre surface, allowing wicking by capillary action to occur. Combined with liquid wicking ability with other properties such as flexibility and wet-strength, thread can be used with other materials to fabricate light-weight and embeddable systems.…”

“…[1][2][3] As part of a continuous effort to seek new materials for making low-cost diagnostic devices, threads and fabrics have been investigated as a group of inexpensive materials for the fabrication of disposable microfluidic devices. [4][5][6][7][8] Thread normally refers to twisted fibers and can be combined to make a yarn. The voids between these fibres form capillary channels and facilitate liquid flow without the requirement of external pumping, make them suitable for fabricating rapid and inexpensive point-of-care (POC) diagnostics.…”