We introduce air-liquid interface-induced deformability cytometry—a technique that enables both static and dynamic deformability measurements in live cells ex-vivo. We use the air-water interface (σ ~0.07 N/m) to deform Red Blood Cells (σ ~0.02 N/m) in micro-channels. The static mode measures the stiffness of a single cell by calculating change in the Laplace pressure. The dynamic mode allows high throughput deformability measurements (>100 cells/s) of Deformability Index (DI) and transit time for tunable air-liquid interface constriction widths. The adjustments in constriction width can be made in real time and can be tuned to widths as small as 2 µm by controlling the air-flow. The mechanical response of cells to different constriction widths was measured and significant difference in DI and transit time was observed for constriction widths < 4µm. The technique also eliminates the cell-substrate interactions due to the presence of virtual wall and thus providing insights into mechanical response of the cells. The technique can be used for different cells with comparable sizes thereby offering flexibility and scalability.

Kotesa, R. S., Ananthasuresh, G. K., & Sen, P. (2017). Air-Liquid Interface-Induced Deformability Cytometry, 2, 685–686. The 21st International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2017

Kotesa, R. S., Ananthasuresh, G. K., & Sen, P. (2016). Probing Erythrocyte Deformability Using A Microfluidic Cell-Squeezer For Mechanodiagnostics, 2, 633–634. The 20th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2016

Kotesa, R. S., Rattan, K., Ananthasuresh, G. K., & Sen, P. (2018), Real Time Measurement of Deformability Index for Electro-Mechanodiagnostics, 13th IEEE Conference on Nano/Micro Engineered and Molecular Systems, Singapore, NEMS 2018 (Accepted Oral)

Flagellar propulsion is observed extensively in nature and has been proposed as a means of propelling nanoswimmers, which may possess tremendous potential in medical applications. Natural flagellum actively consumes energy in order to generate bending moments that sustain constant or increasing amplitude along their length. The flagellum propels either through a planar wave or through a helical wave. In the present work, an elastohydrodynamic model of a tapered flagellum propelling through a helical wave is proposed and is used to obtain the steady state shape. A modified resistive force theory is used to study the propulsive dynamics of a tapered flagellum. A tapered flagellum facilitates higher velocity and efficiency due to reduction of drag at the tapered end. The optimal size and shape parameters are found for the fastest and efficient nanoswimmer.

The propulsion characteristics of a tapered flagellum propelling through helical wave is compared to a similar flagellum propelling through planar wave propulsion. Though investigation of actuation modes has been done for uniform flagellated nanoswimmers but its influence on tapered flagellated nanoswimmers is not yet addressed. Parametric study with respect to elasticity of flagellum material and its actuation frequency is also analyzed. A tapered flagellum exhibiting planar wave propulsion is found to facilitate higher efficiency than helical wave propulsion for the same simulation parameters. The planar wave is found to faster than helical wave for lower values of taper ratio whereas helical wave is superior for higher taper ratios.

Kotesa, R. S., Rathore, J. S., & Sharma, N. N. (2013). Tapered Flagellated Nanoswimmer: Comparison of Helical Wave and Planar Wave Propulsion. BioNanoScience, 3(4), 343-347. Link

Kotesa, R. S., Rathore, J. S., & Sharma, N. N. (2015). Investigations on a tapered flagellated nanoswimmer propelling through a helical wave. In Humanoid, Nanotechnology, Information Technology, Communication and Control, Environment and Management (HNICEM), 2015 International Conference on (pp. 1-6). IEEE.