Open Surface Microfluids

Surface engineering is a fascinating aspect of the wettability manipulation of surfaces. Engineering of surfaces can be done in micro-scale, nano-scale, or the mix of two which is known as a hierarchy. The energy of a surface can be controlled by manipulating the surface morphology. We work on the fabrication of superhydrophobic and superhydrophilic surfaces which are biocompatible and can also be used for energy harvesting. Along with that, we are also working on wettability patterning using chemical treatment, laser ablation, and lithography techniques to manipulate interfaces on open surface platform.

Liquid/droplet manipulation on an open surfaces such as mixing, transport and splitting has a broad range of applications starting from condensation, electronic chip cooling to Lab-on-a-chip system and point-of-care diagnostics. A better understanding of the droplet behavior during the manipulation on an open surface is very much essential for optimizing the method of droplet manipulation. Generally, a droplet/liquid can be manipulated on an open surface with the help of external energy, whereas it is also possible to manipulate a droplet passively. Few passive droplet manipulation techniques are 1) By creating a gradient of wettability on the surface either by creating texture gradient (physical) or by creating energy gradient (chemical) on the surface, and, 2) By creating shape gradient surface. The droplet moves on such surfaces due to the Laplace pressure difference across the droplet. We work on optimization of open surface passive droplet manipulation techniques using both numerical simulation and experiments.

Liquid spreading on open surfaces is a widely observed phenomenon. Liquid spreading becomes complex when the surface is porous. The physics of liquid spreading in paper or fabrics is more complicated due to the evaporation of liquid and swelling of the fibers. The Lucas-Washburn model was developed to predict the capillary rise in porous media by considering it as a bundle of capillary tubes. But in the practical scenario, the L-W model is failed to predict the accurate liquid front for a longer time. Our main aim is to study the capillary rise of liquid through deformable porous media experimentally, numerically, and analytically so that we can understand the complex phenomenon easily.

Food adulteration is a serious issue worldwide and gained high attention from the food safety authority, as is it harmful to public health. Milk is one of the most contaminated food in developing countries, which produce about 50% of the total milk worldwide, such as India, Pakistan, China, Brazil, etc. The consumption of milk is high as it is a low-cost nutritious food with high content of protein, fat, carbohydrate, vitamin, minerals, etc. To overcome the gap between the demand and supply, adding adulterants make this business profitable. To solve this enormous problem, we have developed a simple, low-cost, paper-based microfluidic device that can detect multiple adulterants in milk samples simultaneously by colorimetric detection.