(37e) Woven Fabric As a Low-Cost Microfluidic Platform for Tuned Electrophoretic Separations

Low-cost microfluidic devices have been widely researched as potential ways to making medical diagnostics and therapeutic monitoring more accessible to low income and low resource areas of the world. Current approaches to low cost device manufacture involve the assembly of materials such as chromatographic paper into microfluidic devices using multiple step approaches or microfabrication techniques such as UV-photolithography, which are expensive and difficult to scale up. In prior work, we demonstrated a textile weaving-based approach that makes use of this scalable and readily accessible technology to manufacture microfluidic devices in a single step. Liquid flow was tuned in these devices by manipulating the wetting characteristics and chemical treatment imparted to yarns in a seamless manner along the length of the fabric.

In recent work, we leveraged this tuning ability to manufacture fabric-based electrophoretic devices for the separation of mixtures of proteins. Electrophoresis is widely used for the pre-concentration, separation and assay of protein analytes in complex samples. We present the ability to tune separation resolution using the surface properties (wetting characteristics) and the packing density (number of yarns per unit area) of both woven and knit fabrics. These properties can be used to control sample dispersion. For instance, the use of hydrophilic yarns, such as cotton, in the separation channel allows a mixture of anionic dyes to migrate under the influence of an applied electric field, but disallows their separation. The converse is true for hydrophobic materials such as nylon and polyester, with greater packing densities resulting in well resolved separations and greater hydrophobicity resulting in faster separations. For dilute samples, a well known electrophoretic technique termed ‘isotachophoresis’ precedes separation. In this coupled method, a system of electrolytes of differing electrophoretic mobility are used in the buffer in order to first pre-concentrate (or stack) the proteins in the sample, following which the stacked sample  is separated into sharp and well-resolved protein peaks. In gel electrophoresis, the separation event is triggered by a step change in pore-size and pH. We present the use of a seamless transition in yarn surface properties and packing density to perform protein sample pre-concentration followed by separation in a single fabric device. This forms the first instance of sample pre-concentration coupled with electrophoretic separation in a chromatographic platform, with potential applications in the detection of low abundance (rare) protein markers from clinical samples at the point-of-care or in low resource settings.