Research Work

This work estimates Michaelis–Menten kinetics parameters for nutrient transport under varying flow rates in the soft roots of Indian mustard (Brassica juncea) using a plant fluidic device. To find the metallic components within the roots, inductively coupled plasma mass spectrometry (ICP-MS) analysis was performed. The flow rate-dependent metabolic changes were examined using Raman spectral analysis. In addition, three-dimensional numerical simulations were conducted to assess mechanical stresses resulting from the concentration difference that enhances osmotic pressure and flow loading at the root–liquid interface. This study uses a fluidic device that replicates hydroponic conditions for the first time in order to evaluate the convection-dependent Michaelis–Menten kinetics of nutrient uptake in plant roots.

The initial emergence of the primary root from a germinating seed is a pivotal phase that influences a plant's survival. Abiotic factors such as pH, nutrient availability, and soil composition significantly affect root morphology and architecture. Of particular interest is the impact of nutrient flow on thigmomorphogenesis, a response to mechanical stimulation in early root growth, which remains largely unexplored. This study explores the intricate factors influencing early root system development, with a focus on the cooperative correlation between nutrient uptake and its flow dynamics. Using a physiologically as well as ecologically relevant, portable, and cost-effective microfluidic system for the controlled fluid environments offering hydraulic conductivity comparable to that of the soil, this study analyzes the interplay between nutrient flow and root growth post-germination. The findings hold implications for comprehending root responses to changing environmental conditions, paving the way for innovative agricultural and environmental management strategies. 

This study experimentally investigates the effect of lead (Pb2+) contamination on the roots of an Assamese rice line variety Lachit using a heavy metal analyzing fluidic tool. To demonstrate the adverse effects of lead contamination on rice seedlings in a controlled environment, we have performed a number of multidisciplinary experiments. Also, we develop a numerical model in this endeavor to predict the Michaelis–Menten kinetics parameters, which are used to depict the lead transport phenomenon following soft root structure-media flow interactions. We show that increased inlet lead concentration of the media solution leads to a reduction in root growth exponentially in the developed fluidic device. As supported by the Raman spectra analysis, the drastic metabolic changes are visible under lead contamination. The inferences drawn from the current research shed light on the detrimental effects of lead contamination on rice roots, which have the potential to significantly lower agricultural yields and threaten food security in areas where rice is the primary food source. 

This study introduces an innovative Grade 1 paper-based microfluidic device designed for the rapid, sensitive, and cost-effective detection of methanol in alcoholic beverages. The device integrates chemical reagents and sample fluid on a single paper strip, facilitating a straightforward and portable testing mechanism. The detection of methanol is achieved through a colorimetric reaction involving potassium permanganate, sulfuric acid, sodium bisulfite, and chromotropic acid. Upon interaction with methanol, the reagent mixture produces a distinct color change to purple, which can be visually assessed or quantified. The device works well with small sample volumes (usually less than 50 μl), making it ideal for field applications with minimal resources. This paper-based technology provides various benefits compared to conventional methods, such as lower expenses, simplicity of operation, and the possibility of large-scale manufacturing and distribution in areas with limited resources. 

This study investigates energy generation from salinity gradients inside a nanopore that is connected to reservoirs at both ends. The inner wall surfaces are grafted with a densely grafted polyelectrolyte layer (PEL). The PEL grafting density-dependent correlation of dielectric permittivity, molecular diffusivity, and dynamic viscosity is developed in this endeavor. Using these correlations, the finite element framework is employed to solve the equations describing the ionic and fluidic transport. The study uses a partially hydrolyzed polyacrylamide polymer solution, which exhibits a shear-thinning fluid, in combination with the KCl electrolyte for energy-harvesting analysis. The findings of this endeavor demonstrate how the ion-partitioning effect lowers the screening effect and raises the electrical double layer (EDL) potential by reducing the counterions in PEL. Inferences of this analysis are deemed pertinent in designing the nanoscale device intended for high and efficient osmotic energy generation. 

In this work, the tangential (swirl) velocity component is superimposed at the intake of a narrow fluidic cylindrical pipe to achieve the desired mixing of inelastic non-Newtonian fluids/solutes at the outlet. We discuss an analytical method for obtaining the swirl velocity profile, considering the nonlinear viscous effects for both shear-thinning and shear-thickening fluids, represented by the power-law model. We numerically solve the species transport equation, coupled with the analytically derived swirl velocity, using our in-house developed code for the concentration distribution in the flow field. The results show that the inlet swirl and an increase in the shear-thinning fluid property improve advection-dominated mixing. Additionally, higher Reynolds numbers significantly enhance advection's dominance, as more rotation leads to the generation of vortices, resulting in an engulfment flow (chaotic convection) based mixing. We demonstrate that considering the increase in the shear-thinning fluid property with swirl intake reduces the amount of mixing time required in the convective regime. 

The challenges of food security are exacerbated by the world's expanding population and diminishing agricultural land. In response, hydroponic cultivation offers a potentially more sustainable approach to growing nutrient-dense crops compared to traditional methods. Motivated by this understanding, we conducted a series of experiments to explore the behavior of Brassica juncea (Pusa Jaikisan) plant roots under various flow configurations within a controlled environment. The flow configurations considered were no-flow/flow (NF/F), continuous flow, flow/no-flow (F/NF), and stagnation. Additionally, we conducted anatomical sectioning of plant roots to study how different flow configurations affect the cellular structure of the plant root cross section. We also performed numerical simulations to investigate the internal stress generated within plant roots under various flow conditions. We infer that in hydroponic cultivation, altering the flow configuration to a F/NF type could be more cost-effective with less nutrient solution wastage, promoting better plant root growth compared to a continuous flow scenario. 

Capillary wicking in a thicker gel blot microfluidics paper has been investigated through a combination of an analytical framework, experiments, and numerical simulations. The primary objectives of this work are to investigate the concentration-dependent wicking process inside thicker microfluidic paper and to estimate the concentration-dependent permeability using both theoretical models and experimental data. An additional goal is to estimate the parameters for saturation-dependent flow modeling in thicker microfluidic paper. To comprehend the wicking phenomenon on thicker gel blot paper, a series of experiments employing aqueous food dye solutions at varying concentrations has been conducted. In order to calculate the temporal wicking length analytically, the Brinkman-extended Darcy equation is implemented. By modifying the permeability expression for a simple rectangular unidirectional fiber cell and pure liquid, the expression of effective permeability for the analytical framework has also been introduced. The results of the current study can be used to design low-cost paper-based diagnostic devices for usage in healthcare and environmental applications. 

For liquids used in biological applications, a smaller diffusion coefficient results in a longer mixing time. We discuss, in this endeavor, the promising potential of the AC electrothermal (ACET) effect toward modulating enhanced mixing of electrolytic liquids with higher convective strength in a novel wavy micromixer. To this end, we develop a modeling framework and numerically solve the pertinent transport equations in a three-dimensional (3D) configuration numerically. We find that the maximum temperature increase in the wavy micromixer, owing to the electrothermal effect, is less than 10 K even for the higher strength of the applied voltage, implying nondegradation of biological substances within the liquid sample. We report that the formation of significant lateral flow closer to the electrodes leads to a highly three-dimensional ACET flow field, which has a significant impact on the mixing efficiency for the range of diffusive Peclet numbers considered. The results of this study seem to provide an adequate basis for the design of a novel micromixer intended for enhanced solute mixing in realistic microfluidic applications. 

Viscoplastic fluids flow through a microfluidic channel having a built-in two-part cylinder inside, while the upstream and downstream parts of the cylinder bear the surface potential of the same sign but of different magnitudes. We consider the Herschel-Bulkley model in describing the rheology of the viscoplastic fluids considered in this analysis. Consistent with the finite element method, the modeling framework employed here considers the prevailing effect of fluid rheology, and geometrical configuration−modulated electroosmotic forcing while solving the transport equations governing the mixing dynamics. We demonstrate that electroosmotic forcing, induced from the topology-modulated electrical double-layer effect, upon interacting with the prevalent viscous force in the field, leads to the flow reversal in the region closer to the built-in cylinder, which in turn, gives rise to the formation of vortices therein. As seen, the shear-thinning nature of the viscoplastic fluid results in an enhancement of the recirculation velocity strength, albeit the inevitable yield stress of the fluid sparsely influences the onset of flow recirculation. Also, the characteristic time for shear-induced binary aggregation that illustrates the underlying mixing of fluids containing biomolecules, such as proteins and DNAs, is calculated based on the maximum strain rate. 

Root growth dynamics is an outcome of complex hormonal crosstalk. The primary root meristem size, for example, is determined by antagonizing actions of cytokinin and auxin. Here we show that RAV1, a member of the AP2/ERF family of transcription factors, mediates cytokinin signaling in roots to regulate meristem size. Therav1mutants have prominently longer primary roots, with a meristem that is significantly enlarged and contains higher cell numbers, compared with wild-type. The mutant phenotype could be restored on exogenous cytokinin application or by inhibiting auxin transport. At the transcript level, primary cytokinin-responsive genes like ARR1, ARR12 were significantly downregulated in the mutant root, indicating impaired cytokinin signaling. In concurrence, cytokinin induced regulation of SHY2, an Aux/IAA gene, andauxin efflux carrier PIN1 was hindered inrav1, leading to altered auxin transport and distribution. This effectively altered root meristem size in the mutant. Notably, CRF1, another member of the AP2/ERF family implicated in cytokinin signaling, is transcriptionally repressed by RAV1 to promote cytokinin response in roots.

We report the breakup dynamics of a magnetically active (ferrofluid) droplet in a T-shaped Lab on a Chip (LOC) device under the modulation of a non-uniform magnetic field. We adhere to high-speed imaging modalities for the experimental quantification of the droplet splitting phenomenon, while the underlying phenomenon is supported by the numerical results in a qualitative manner as well. On reaching the T-junction divergence,the droplet engulfs the intersection fully and eventually deforms into the dumbbell-shaped form, making its bulges move towards the branches of the junction. We show that the non-uniform force field gradient allows the formation of a hump-like structure inside the left moving bulge, which triggers the onset of augmented convection in its flow field. We reveal that this augmented internal convection developed in the left moving volume/bulge, on becoming coupled to the various involved time scales of the flow field, leads to the asymmetric splitting of the droplet into two sister droplets. Inferences of the present analysis, which demonstrates a plausible means of independently controlling the size of the sister droplet by manoeuvring the applied force field gradient, will provide a potential solution for rapid droplet splitting, which typically finds significant importance in point-of-care diagnostics.