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Pumping fluids without an aid of an external power source are desirable in a number of applications ranging from a cooling of microelectronic circuits to Micro Total Analysis Systems (micro-TAS). Although, several microfluidic pumps exist, yet passive micropumps demonstrate better energy efficiency while providing a better control over a pumping rate and its operation. The fluid pumping rate and their easy maneuverability are critical in some applications; therefore, in the current work, we have developed a leaf-mimicking micropump that demonstrated ~6 fold increase in a volumetric pumping rate as compared to the micropumps having a single capillary fluid delivery system. We have discussed a simple, scalable, yet inexpensive method to design and fabricate these leaf mimicking micopump. The microstructure of the micropumps were characterised through scanning electron microscopy and its pumping performance (volumetric pumping rate and pressure head sustainence) were assessed experimentally. The working principle of the proposed micropump is attributed to its structural elements; where branched-shaped microchannels deliver the fluid acting like veins of leaves while the connected microporous support resembles mesophyll cells matrix that instantaneously transfers the delivered fluid by a capillary action to multiple pores mimicking the stomata for evaporation. Such design of micropumps will enable an efficient delivery of the desired volume of a fluid to any 2D/3D micro/nanofluidic devices used in an engineering and biological applications., Comment: 19 pages including 6 figures and 1 table. The The work was presented as an oral presentation in the National conference on Convergence of Pharmaceutical Sciences and Biomedical technology, 2018, National Institute of Pharmaceutical Education and Research, Ahmadabad, India ( 26th March - 28th March, 2018)

Fish gills are one of the most primitive gas/solute exchange organs, having the highest ventilation volume, present in nature. Such performance is attributed to a functional unit of gill - secondary lamella - that can extract oxygen from an ambience even at a very low partial pressure. For centuries, gills have stood as one of the simplest but an elegant gas/solute exchange organs. Although the role of various morphometric factors of fish gills on gas/solute exchange capabilities have been reported, there has been limited understanding on what makes fish gills as an excellent gas/solute exchange system. Therefore, in the current study, we have theoretically studied the variation of few structural and parametric ratios, which were known to have role in gas/solute exchange, with respect to the weight of fishes. Thereafter, modelling and simulation of convection-diffusion transport through a two dimensional model of secondary lamella were carried out to study different factors affecting the performance of gills. The results obtained from both the studies (theoretical and computational) were in good agreement with each other. Thus, our study suggested that fish gills have optimized parametric ratios, at multiple length scales, throughout an evolution to arrive at an organ with enhanced mass transport capabilities. Further, our study also highlighted the role of length of primary and secondary lamella, surface area of secondary lamellae and inter-lamellar distance on gas/solute exchange capabilities of fish gills. Thus, these defined morphological parameters and parametric ratios could be exploited in future to design and develop efficient gas/solute exchange microdevices., Comment: 18 pages, 7 figures, A part of results published as Kumar P, P S Gandhi, M Majumder, Design and fabrication of thin microvascularised polymer matrices inspired from secondary lamellae of fish gills,""Bioinspiration, Biomimetics, and Bioreplication VI", an international conference, SPIE/NDE, (Las Vegas, USA), 9797-40, 2016

Integrated micro-nanochannel networks in fluidic devices are desirable in a number of applications ranging from self-healing/cooling materials to bioengineering. The conventional micro-manufacturing techniques are capable of either producing microchannel or nanochannel networks for a fluidic application but lack proficiency in the production of an integrated micro-nanochannel network with a smooth transition from micro-to-nano scale dimension. In addition, these techniques possess limitations such as heavy initial investment, sophistication in operation and scale-up capabilities. Therefore, the current paper demonstrates the combination of micro/nanotechnologies to design and develop a biomimetic 3-D integrated micro-nanochannel network in PDMS device for solute exchange. We have used 3-D printer, a scalable technology, to design and manufacture micro-mold having fractal-shaped features. Further, electrospinning was used to deposit nanofibrous network on the fractal mold. Subsequent micro-molding with PDMS was used to obtain fractal-shaped microchannels integrated with embedded nanofibers. Henceforth, solvent etching of nanofibers followed by bonding of thin PDMS membrane generated by spin coating to open end of channels leads to the formation of functional microdevices. These PDMS devices mimic the natural vasculature of a living system, where fractal-shaped microchannels will assist in efficient fluid flow and the site of nanovascular network participates in heat/mass transport operations. Further, dye flow propounds the functionality of such devices. Our study hence proposes a simple and scalable hybrid microtechnolgy to fabricate fluidic devices having multiscale architecture. This will also facilitate the rapid fabrication of microfluidic devices for biomedical, diagnostics, sensors and micro-TAS applications., Comment: 5 pages, 5 figures, conference proceedings in 11th International Conference on MicroManufacturing, UC Irvine, 2016