Name of the Student: Praneet Prakash
PhD Supervisor: Prof. Manoj Varma
Venue: Third Floor Class Room , CeNSE
Date/Time: 28-09-2018, 10:00 am
ABSTRACT
Life forms as we know emerged due to unique mechanical and transport properties exhibited by Soft Materials at the interface. For instance, the interior of a cell is separated from outside environment by lipid bilayer which self-assembles in aqueous environment due to hydrophobic and hydrophilic ends. Examples of interfacial system includes polyelectrolyte multilayers, gel, colloid, surfactant, liquid crystal, variety of biological materials, bacterial systems etc. In this talk, we will set out to understand transport in bioinspired interfacial system which are crucial for a variety of applications. Specifically, I will discuss:
a) The role of analyte transport and reaction kinetics in dictating sensitivity and specificity of surface-based Biosensors – Early identification of disease requires development of highly sensitive and specific detectors. Blood which is the common source of biomarkers has numerous entities which puts stringent requirements on sensitivity and specificity of sensors. We numerically studied surface based microfluidic sensing platform to analyse the reaction and flow parameters most suited for a sensitive and specific detection.
b) Limitations of ‘Fluorescence Recovery After Photobleaching’ (FRAP) technique in estimating transport properties of ultrathin polyelectrolyte multilayer films – FRAP is one of the most widely used technique to estimate transport parameters in biological cells and polymer films. A region of interest is irreversibly photobleached using high incident optical power and, thereafter, fluorescent recovery is initiated by fluorophores diffusing from the surrounding ‘fluorophore rich’ regions. The measurement of fluorescence recovery as a function of time enables the estimation of diffusion coefficient. An important conclusion from our numerical and experimental study is that, for ultrathin films of 100 nm thickness, classical FRAP analysis is not sufficient to probe diffusion.
c) Fluid flow and Vander Waals force mediated pinning of polystyrene beads over microstructured substrate – We studied flow profile of polystyrene microspheres (5 – 10 um) over crest shaped microstructures (height = 1 um) on glass substrate. A symmetry breaking in the flow profile of microsphere occurs at moderate Reynolds number (1 – 5) which leads to the pinning of microspheres in downslope region. Further, a rapid flocculation of binary sized flowing mixture of microspheres occurs at high flow rates. The morphology of these microstructures is similar to the shape of plaque build-up in arteries, hence, these experiments suggest an important role of arterial morphology and size distribution of cellular debris in plaque formation.
d) A non-chemical technique to attach and transport cargo on bacteria – Bacteria are the smallest (1 um) living machines which are able to forage, communicate, and respond actively to the external stimuli. Researchers have shown cargo delivery by bacteria using chemical means, where, chemically coated microspheres stick to bacteria due to electrostatic interaction. Use of chemicals has compatibility issues and is not universal. We have developed a purely physical approach to attach oil droplet as cargo via sonication of entrapped bacteria on oil-water interface. These, cargo carrying bacteria can manoeuvre through obstacles and are able to transport oil droplets of size as large as 10 um.