(4k) Optical and Electric Forces At Nano-Structures and Interfaces: Novel Spectroscopic Sensors From Single Molecule Dynamics to Diagnostic Platforms

Basuray, S., University of Missouri

Polarization mechanisms and charge dynamics at interfaces and near geometric singularities drive a multitude of spatiotemporal phenomena from slow ionic charge accumulation to rapid photonic coupling. This leads to highly specific potential gradients that can drive a host of physical phenomena such as dielectrophoresis, electro-wetting, plasmonics and photonics. This spatial characteristic of the electric and optical field can be dynamically controlled by precise modulation of the geometric singularity of the structures in real-time.

                In my future work, I intend to develop a new class of adaptive, stimulus responsive sensors constructed out of immiscible fluids, polymers, nano-particles to create sensitive, cheap, robust, nano-ordered and non-linear optical components. These self-sustaining sensors will be used for real time monitoring of in-situ bio-molecular dynamics, water quality and nutrient sensors. For example, dynamically discerning subtle changes in cell secretions as pathological indicators. However, to achieve this objective, it will require novel and creative application of optical (surface plasmon resonance (SPR), both short and long range) and electrical (electrochemical impedance spectroscopy (EIS), micro and nano-fluidics) forces to create dynamic interfaces. These interfaces can trap, focus and concentrate molecules, recognizing the benefits of the singular electric field arising out of optical coupling at geometric singularities. The designing of such sensors will require developing fundamental knowledge and research into material characterization, fluidics, optics, electro-kinetics, nanotechnology specifically their interaction through simulations and theoretical insights. Label-free identification methodologies from Surface Enhanced Raman Spectroscopy (SERS) to EIS, will allow the sensors to be wearable and adaptable for low-resource settings. Further, sophisticated optics will allow for sufficient spatial and temporal resolution to simultaneously scrutinize and observe (detect) complex biological kinetics over broad spatial and temporal scales with single molecule resolution.

                My inspiration for the novel sensor methodology arises from my doctoral research into interfacial electro-kinetics and its application to bio-diagnostic platforms through geometric singular surfaces. I identified the origin of Stern Layer by critically revisiting classical theories and was the first person to show the double layer effects and dynamics on size-dependent dielectrophorestic behavior of nano-scale colloids. I used these fundamentals to develop label-free, sensitive, ultra-selective EIS based diagnostic microfluidic platforms and a novel qualitative and quantitative EIS nanofluidic nucleic assay as an alternative to qPCR, ­that have since led to entrepreneur startups.

                In my post-doctoral work, I extended my foray to study optics specifically the interaction of bio-molecules with localized SPR and photonic waveguides through Fluorescence correlation spectroscopy (FCS), molecule-metal interactions, Förster resonance energy transfer (FRET) and SERS.  A novel stamping process coupled with an intelligent metal deposition process was developed to fabricate nano-ordered surface morphology on a plasmonic grating and nano-defects in a 1-D photonic crystal, without using expensive nano-lithography. Both show extra-ordinary broad spectrum electromagnetic enhancement due to line and point defects. Enhancements to multiple spectroscopic techniques, from SERS to FCS using only an epi-fluorescence microscopy, were achieved from a single platform.

Teaching and Outreach:

  •  I manage the biological lab and material characterization lab at the Center for Nano-Micro Systems and Nanotechnology at the University of Missouri, Columbia, where I also train students on different characterization instruments like AFM, UV-VIS, Raman, Ellipsometer and Dynamic Light Scattering.
  • I was a research scientist in the new technologies team for the development of third, fourth generation genetic sequencers at Roche, a pharmaceutical company.

Developed and taught a number of courses and labs, like undergraduate chemical engineering senior year lab, advanced applied mathematics, developing the lab portion of a microfluidics course.