Research Projects

Rheology (both oscillatory and extensional) and tensiometry of different colloids and viscoelastic fluids are crucial across understanding a wide gamut of fluid dynamic events in natural, industrial, and biological systems—e.g., magma, lava, sludge, slurries, mucous, blood, lymph, pus, bone marrow, sap, rubber, cream, food matter, detergents, solvents, starch solution, oils, syrup, etc. Rheometry-tensiometry data gives insight into the fundamental fluid properties, directly impacting food processing and safety, slurry transport, healthcare and pharma-industry, polymers, fast-moving-consumer-goods (FMCG), additive manufacturing, etc. Determining relaxation timescales and interfacial tensions is critical for understanding complex fluid dynamics and associated thermo-solutal transport. However, traditional rotational/extensional rheometers and tensiometers are costly, bulky, require constant maintenance, and incompatible with conductive/corrosive liquids. Also, complex fluids (ER and MR fluids) demand specialized equipment that is unavailable, especially for extensional rheometers and for tensiometry. Today, an ER-MR-rotational rheometer costs around INR 1 crore plus. A extensional CaBER (no electro-magnetic modules commercially available) costs around INR 80 lakhs plus. A Tensiometer (no electro-magnetic modules commercially available) costs around INR 20 lakhs plus. This project proposes benchtop, cost-effective alternatives using high-speed imaging to eliminate dependency on traditional rheometry/tensiometry tools, for analyzing relaxation dynamics and interfacial behaviour, using principles of microfluidic manipulation and droplet hydrodynamics. With the current platforms being envisaged, a simple high speed camera (INR 24 lakhs), a high voltage module (INR 2 lakhs), and electromagnet assembly (INR 4 lakhs), and microfluidic pumps and dispensers (INR 5-6 lakhs in total) will be sufficient to obtain the required results for all 3 types of studies (hence a total of INR 35-36 lakhs, against total of 2 crores plus in the previous cases). The project will lead to output that will help research groups realize and develop similar platforms for their end-uses, if they have such microfluidic systems available in their labs. We will design, develop, validate and experiment on two platforms utilizing optical diagnostics of microfluidic manipulation: I. DEM-CoRT (Droplet-Electro-Magneto-Coalescence-Rheometry and Tensiometry) – will enable relaxation timescale estimation and detailed tensiometry and interfacial dilation II. CaB-ME-FER (Capillary–Breakup–Magneto–Electro–Filament–Extensional–Rheometry) – will enable extensional viscoelasticity experiments and elongational rheometry studies These platforms will analyze microdroplet coalescence and capillary-filament dynamics, including temperature-controlled rheo-tensiometric measurements. Validation will be performed using rheometry and tensiometry data from standard market-available equipments, covering Newtonian to highly viscoelastic fluids, and weakly to strongly surface-active materials (e.g., surfactant and colloidal systems). Once validated, different novel fluidic systems shall be studied. Next, we will integrate a high-voltage electric field module into both platforms to enable electro-rheological and electro-tensiometric measurements. These will be benchmarked against standard electro-rheometers (electro-tensiometers are not available in market). The goal is to then perform detailed experiments on understanding relaxation dynamics and electro-interfacial tension in Newtonian, viscoelastic, and colloidal ER fluids under electric fields. Finally, we will add a digital magnetic field generator for magneto-rheology and magneto-tensiometry studies. These will also be validated against standard setups (magneto-tensiometry not available in market), enabling advanced exploration of relaxation times and magneto-interfacial tension in complex magneto-responsive fluids and MR fluids.