Rapid and Automated Measurement of Milk Adulteration Using a 3D Printed Optofluidic Microviscometer (OMV)

In developing countries like India, adulteration in the milk consumed by the population presents stern implications as tarnishing of the same poses serious issues, such as health deterioration, corruption, and so on. There are many adulterants that are added to milk, including water, flour, starch, and even urea, in quantitative measures making it undetectable. There are many devices in the market to measure adulteration in milk but most of them are bulky, require large sample volume, and need a technical operator for working. In the recent decade, microfluidics has emerged as a huge market for biomedical research. It has paved the pathway for a quick, robust, and plug-and-play device for various applications. This paper describes a low-cost, durable, and simple optofluidic microviscometer fabricated by the stereolithography technique. The device operation is based on the linear relationship between dynamic viscosity and channel width derived from the flow of two immiscible fluids inside a channel. The principle of operation is based on the modified Hagen-Poiseuille flow equation. The working principle is the viscosity-dependent capture of the microchannel width by the fluids flowing inside the microchannel under the laminar flow based on the pressure gradient between the inlets and the outlet. In this paper, around 60 milk samples with various adulteration ratios of various adulterants ranging from 1% to 10% have been tested. A best fit curve for every adulterant was defined, and the device was found to be accurate enough to measure the entire range of adulteration ratios with a high accuracy of 0.95.