Laser-based patterning for fluidic devices in nitrocellulose

Abstract

In this report, we demonstrate a simple and low cost method that can be reproducibly used for fabrication of microfluidic devices in nitrocellulose. The fluidic patterns are created via a laser-based direct-write technique that induces polymerisation of a photo-polymer previously impregnated in the nitrocellulose. The resulting structures form hydrophobic barriers that extend through the thickness of the nitrocellulose and define an interconnected hydrophilic fluidic-flow pattern. Our experimental results show that using this method it is possible to achieve microfluidic channels with lateral dimensions of $100 lm using hydrophobic barriers that form the channel walls with dimensions of $60 lm; both of these values are considerably smaller than those that can be achieved with other current techniques used in the fabrication of nitrocellulose-based fluidic devices. A simple grid patterned nitrocellulose device was then used for the detection of C-reactive protein via a sandwich enzyme-linked immunosorbent assay, which served as a useful proof-of-principle experiment.

Laser direct-write for fabrication of three-dimensional paper-based devices

“…The basic LDW setup is the same as described in our previous publications for fabrication of 2D microfluidic devices and implementation of flow-control and has been fully optimised via a series of systematic studies. [21][22][23] The results we have achieved and will report in the following sections are therefore based on the same patterning procedure with appropriate adjustment of the patterning conditions such as laser power and scan speed.…”

“…This innovative result presents a solution for not only sealing of paper-based devices by isolating the device between dissimilar outer cladding layers but also, most importantly, permitting 3D pathways to be engineered through judicious assembly of several layers, possibly combined with holes and voids in some layers. In our earlier publications using the same laser-direct write technique, 21,22 we have demonstrated the patterning of varied porous materials such as nitrocellulose membranes, printing paper, fabrics, and we therefore believe that any such material which is porous in nature would be suited for use in the production of the above described multi-layer devices. There are no other requirements that we believe would limit the use of a specific type of material for the creation of multi-layered devices.…”

“…21,22 Through selectively designing and patterning polymerised structures from both sides of the substrate, we could fabricate 3D structures inside a single substrate. Unlike other 3D device fabrication methods, the approach presented here does not require any additional processing equipment or alignment/assembling step and uses the same fabrication approach described earlier for producing a 2D fluidic device.…”

“…[21][22][23] In brief, by controlling the laser patterning conditions, we have shown that we can produce solid hydrophobic structures either partially inside a single layer of paper or all the way through several layers of paper (we have so far demonstrated 3 separate layers). Also, by selectively patterning from both sides of the composite substrate, we have fabricated 3D devices based on both a single layer as well as a multi-layer stacked arrangement.…”

Organic Solvent and Surfactant Resistant Paper-Fluidic Devices Fabricated by One-Step Embossing of Nonwoven Polypropylene Sheet

“…Fluidic channels can also be formed by printing hydrophobic agents [ 9 , 10 ] on hydrophilic substrates or etching agents on hydrophobic substrates [ 11 ]. Other creative methods were developed using a knife plotter to cut the papers into specific shapes [ 12 ]; a laser to hydrophillize a hydrophobic substrate [ 13 ], to polymerize pre-impregnated photopolymers in the NC membrane to create hydrophobic barriers [ 14 ], or to pattern hollow microstructures to form barriers [ 15 ]. From the many methods of barrier formation, wax printing on chromatography paper is currently one of the most widely used and most promising fabrication methods.…”