Sanket Goel

Integrated optical measurement of microfluid velocity

The integration of multimode ion-exchange waveguides and etched microchannels in glass biochips is described. The waveguides were used to carry laser light to specific points in the channels for the detection of fluorescent microparticles. Anomalous etching was observed at the intersections of the waveguides and the microchannels resulting in the partial etching of the waveguides to form side-channels to the main channels. When filled with fluid, these side-channels have a lower index of refraction than the surrounding waveguides causing the laser light to illuminate the microchannel in two places. It is demonstrated how the double-peaked signal from a passing fluorescent microparticle can be used to directly determine the velocity of the liquid in microchannels.

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.

Biochips with integrated optics and fluidics

Developmental work in the fabrication of microsystems with integrated optics and fluidics is described. For application such as blood flow and blood cell deformability studies, microparticle identification and manipulation, and on-chip chemical analysis, microchannels and waveguides with inner dimensions in the range of 30 - 50 μm are required. Two integration strategies are described: laser-writing of channels and waveguides in UV-curable polymers and fabrication of silver ion-exchange waveguides in glass microchannel biochips. A fiber-fed photomultiple detection system is also discussed.

Optical detection system for biochips using plastic fiber optics

An instrument for the detection of optical signals from microfluidic biochips is described. The light detection system uses a LabView™-controlled photomultiplier tube with a programmable gain of 104–107. Plastic optical fibers (POFs) of 1 mm diameter are used to deliver light to and from the microfluidic systems. The detection system is demonstrated by detecting fluorescence from 15 μm polystyrene spheres in commercial biochips and micropipettes using a custom POF launch and detect tip. The spatial response of the tip allows dynamic measurements of the velocities of the microparticles to be made.

Decentralized distributed generation in India: A review

There is an imperative need of developing new strategies and models for meeting the swelling demand of electricity in developing nations like India. One of the promising models for this would be Decentralized Distributed Generation (DDG). DDG locates the power generating source closer to the consumer utilizing locally available Renewable Energy (RE) resources, thereby decreasing the Transmission and Distribution (T&D) losses. Despite the numerous advantages with DDG, there have been some minor issues preventing its large scale deployment and utilization in India. This paper discusses the various technology options which can be used for DDG in India and the problems which the Indian power sector has been facing for a long time. This paper aims to provide a complete analysis of the best possible RE based technology options for DDG in India along with their cost of generation, benefits, barriers, applications, and the possible pathways for its deployment.

Fabrication of Micro-Optic/Microfluidic Biochips

The development of devices for biological and chemical analysis is a new and exciting application of micro-electro-mechanical systems (MEMS) technology. In this paper, a method for integrating multimode optical waveguides within glass biochips with fluidic microchannels is described. The waveguides buried in the glass are designed to carry probe light to the channels, capture any emission from samples therein, and deliver the emitted light it to a sensitive photodetector. The ultimate goal is a self-contained, operatorless analysis system for mass testing of biological samples. The field-assisted silver ion-exchange process for fabricating the multimode waveguides and some preliminary results on the waveguide properties are described.

Ligand Binding Kinetics of Cell Surface Receptors by Microfluidic Displacement

Cell Surface binding kinetics of bio-molecular interaction is of fundamental importance in advancing our understanding of numerous biological processes and developing bioengineered systems. We have adopted a displacement technique, wherein a ligand is displaced from the binding site, by an excess of a ligand analog perfused through the microchannel. The theoretical model describes transient convection and diffusion in the microchannel volume following dissociation of the ligand from the cell surface receptors. To incorporate living cell processes, the model includes cell surface receptor trafficking. The decay of eluting ligand concentration follows a mono-exponential curve for one receptor sub-type or kinetic dissociation rate constant. A numerical solution is obtained using the method of finite differences and verified with an analytical solution for the case of negligible dispersion. Results illustrate how the fluid velocity and receptor internalization rate influence the ligand concentration at the microchannel outlet. This modeling effort is expected to allow better experimental design and subsequently more accurate measurement of kinetic rate constants.

Lab-on-a-chip optical detection system using plastic fiber optics

A new optical detection system for microfluidic lab-on-a-chip applications is described. The photomultiplier tube (PMT) system is controlled by LabVIEW and has output/primary current gains that are programmable from 104 to 107. Light is delivered to and from microfluidic systems by a custom launch-and-detect fiber probe fabricated from one-millimeter plastic optical fibers. The noise characteristics are descrbied and the detection of fluorescent 15μm polystyrene spheres is demonstrated. Using the measured static spatial response of the tip, the velocities of moving microparticles can be calculated from dynamic measurements of their fluorescence.

Microfluidic Microbial Fuel Cell: On-chip Automated and Robust Method to Generate Energy

Microbial fuel cell (MFC) is a bio-electrochemical fuel cell where microorganisms, such as bacteria and virus, are used to catalyse the redox reaction to generate energy. Due to their inherent process, MFCs lead to the production of green and clean renewable energy in a self-sustainable manner. Even though, humongous work has been carried out in MFC domain leading to the exponentially increasing scientific output over the years, there has been limitation to harness MFC as a viable, workable but cost-effective remedy to the current energy and environmental challenges due to its expensiveness, low performance and challenges to scale-up (Lee et al. 2015a, b; Wang et al. 2015).

Towards rapid prototyped convective microfluidic DNA amplification platform

Today, Polymerase Chain Reaction (PCR) based DNA amplification plays an indispensable role in the field of biomedical research. Its inherent ability to exponentially amplify sample DNA has proven useful for the identification of virulent pathogens like those causing Multiple Drug-Resistant Tuberculosis (MDR-TB). The intervention of Microfluidics technology has revolutionized the concept of PCR from being a laborious and time consuming process into one that is faster, easily portable and capable of being multifunctional. The Microfluidics based PCR outweighs its traditional counterpart in terms of flexibility of varying reaction rate, operation simplicity, need of a fraction of volume and capability of being integrated with other functional elements. The scope of the present work involves the development of a real-time continuous flow microfluidic device, fabricated by 3D printing-governed rapid prototyping method, eventually leading to an automated and robust platform to process multiple DNA samples for detection of MDRTB-associated mutations. The thermal gradient characteristic to the PCR process is produced using peltier units appropriate to the microfluidic environment fully monitored and controlled by a low cost controller driven by a Data Acquisition System. The process efficiency achieved in the microfluidic environment in terms of output per cycle is expected to be on par with the traditional PCR and capable of earning the additional advantages of being faster and minimizing the handling.