Prasoon Kumar’s Defense


Successful Defense of Prasoon Kumar

Prasoon Kumar, jointly guided by Prof. Prasanna Gandhi (IIT Bombay) and Prof. Mainak Majumder (Monash University) presented his defense seminar on Monday, 2 April 2018.

His thesis title is ‘Scalable fabrication of bio-inspired, 3D micro/nanofluidic devices’.

Abstract:

The diffusion of small molecules through polymeric micro/nanosystems finds application in numerous fields such as tissue engineering, biomedical devices, membrane-separation technologies, food-packaging industries and in the removal of contaminants, solvents and such others. The performance of such devices depends on the microstructure of the polymers and the design of the micro/nanosystems that employ the polymers. The design of devices at multiple length scales that are inspired from natural systems has been proven in the manufacture of highly efficient microsystems. However, the scalable fabrication of such micro/nanosystems (with limited costs in instrumentation and operation, and minimal requirement of expertise and time) should be possible before these micro/nanosystems can be used at full throttle in the applications mentioned above.

Therefore, in the current work, we have thoroughly studied the secondary lamella of fish gills at different length scales by using computational and theoretical analysis, in order to determine the structural parameters that are responsible for their excellent gas-/solute-exchange capabilities. Our findings suggested the evolutionary conservation of a few structural factors and parametric ratios in fish gills, which is responsible for the efficient gas/solute exchange capability in every fish. Inspired by the design of secondary lamella, we have fabricated bio- inspired multiscale 3D micro/nanochannel networks in thin polymeric matrices by solvent etching of sacrificial structures that are formed by a combination of two scalable microtechnologies: electrospinning and the controlled, lifted Hele-Shaw method. The fabrication methodology presented here is a lithographyless, ultrafast, scalable process for the generating of multiscale fractal morphologies in polymeric materials. After conducting structural and dye flow characterization of the above mentioned multiscale, 3D micro/nanofluidic devices, preliminary results of their mass-transfer capabilities showed that these multiscale, 3D micro/nanofluidic devices were better in comparison to simple 3D micro/nanofluidic devices. Further, our experimental and theoretical investigation suggested that the geometry of the intermediate channel network (reservoir) plays a vital role in interfacing with a random network of nanochannels for enhanced volumetric fluid flow through them. Further, the densities and the tortuosity of the nanochannel networks also play a vital role in the volumetric fluid flow and mass-transfer capabilities of 3D micro/nanofluidic devices.

Although capillary-driven flow studies were carried out by using the 3D micro/nanofluidic devices that are mentioned above, a passive fluid pump connected to such 3D micro/nanofluidic devices is desirable in order to achieve a better rate of fluid flow. This may result in extending the applications of 3D micro/nanofluidic devices in areas such as μ-TAS, cooling of microelectronic circuits and advance drug delivery. Therefore, we have developed a passive micropump that was inspired by leaves of plants that can pump fluid at a rate comparable with that which is reported in previous literature. In this study, the manufacturing of micropumps also represents a simple, scalable and inexpensive process in which spin-coating technology is integrated with a controlled, lifted Hele-Shaw cell. The micropumps were able to emulate the structural features of leaves and the pump fluid by a coupled phenomenon of capillary action, absorption and evaporation. Further, a theoretical model was developed to describe the micropumping phenomenon. The model elucidates the role of different structural and ambient factors such as designs that are inspired from leaves, the temperature of the ambience, the density of the vascular network, the permeability of a porous substrate and such others for volumetric pumping of fluid and sustaining of the pressure head. The results predicted by the theoretical model corroborated well with the experimental findings. Eventually, the design, fabrication and characterization of the leaf-inspired micropump were successfully carried out.

In summary, in order to exploit bio-inspired micro/nanofluidic devices for mass-transfer operations, the work focused on the design and fabrication of these devices through scalable micro/nanotechnologies; this was done in order to ensure enhanced fluid flow and to study factors that affect the flow of fluid through such devices. Thus, the work will enable the development of 3D micro/nanofluidic at a large scale for applications in biomedical and chemical industry, which demand the transfer of heat and mass.