Currently all my research projects are aimed at addressing different facets of the following questions,
"How can we modularly control the organization of molecule/atoms/nanoparticles in, 2D/3D or within nanofabricated structures, using established scalable technologies? And, what fundamentally new devices and technolgies does this capability enable?"
The work is equal parts curiosity driven (i.e the science/technology is cool) and a desire to develop practical/functional devices. Broadly the work has three main themes,
This addresses the first part of my two part question pertaining to the technology by which we can organize and integrate molecular/atomic scale elements with elements realized by top-down approach. Top-down nanofabrication has helped create almost every electronic/optical devices we use to interact with the world. And, over the last six decades the technology has progressively enabled phenenal miniatuzation, enabling billions of chips to be fabricated with features as small as 13nm (soon to become 10nm). However, the minaturization and complexity enabled top-down pales in comparison to structures formed bottom-up, single atom/molecule at a time. Additionally, there is a large variety of structures that are formed bottom-up (like organic molecules, quantum dots, carbon nanotubes or proteins) that have unique properties unachievable top-down and are also completely incompatible with current top-down fabrication techniques. This also eludes to a more general questions, how can we scalably bridge the molecule/atomic length scale with the length scale that is accessible using current top-down techniques. My insistence of scalability and current technological process is due to my personal desire to work on approaches that can, if successful, enable realization of large number of devices and can be utilized by as many people as possible.
My approach to tackling this problem involves primarily using DNA origami as an adaptor to bridge the bottom-up and top-down nanofabricated elements. DNA origami is a technique developed by Paul Rothemund in 2006 to fold a long ssDNA into arbitrary 2D and 3D nanoparticles with the help of a few hundred short ssDNA strands. This approach also offers unique advantages like 5nm resolution (in principle this can be reduced to 3.4A), control over orientation of molecular elements, immense modularity that can enable heterogeneous components to be assembled. I have already demonstrated some of these capabilities, however many more open questions like the ones listed below still remains unanswered.
- Can we segregate multiple origamis orthogonally on a surface using merely their shapes?
- Is it possible to using the origami to precisely and controllably to deposite a single chemical leaving group on the surface?
- Etching origami shaped features on the surface.
- Mineralization of DNA origami.
- Nucleating crystals (2D and 3D) from defined positions on a surface.
Each of these open questions provides a fundamentally new approach to scalably position individual molecule/atom length scale element within the current top-down nanofabricated devices.
While it is possible to utilize molecular assembly capability to fundamental questions in a multitude of different fields my interest is primarily in its application to nanophotonics (mainly due to my formal training in nanophotonics). Very broadly I am interested in unique optical properties that can be enabled by DNA origami assisted nanofabrication. It includes (but not limited to),
- Superradiance engineering to engineer and study long range interaction between emitters that are positioned inside optical elements
- Phase engineering using metasurfaces created with DNA origami
- Organizing emitters inside photonic crystals with chiral optical modes
- Crystals with single or multiple rare earth ions created using DNA and DNA origami for novel light sources as well as energy harvesting
In addition to the aforementioned directions I am also interested in addressing biological questions using the placement technology as well as DNA origami. The two directions I am thinking and working towards are,
- Creating model systems to study stochasticity in biological networks using the placment technique.
- Studying cellular surfaces using DNA origami.
For my PhD I was working on understanding light localization in aperiodic nanostructures (or disorder depending on your point of view) with the aim of potentially developing label-free bio-sensing devices and also radiative engineering. This was work that I did at Boston University with Prof. Luca Dal Negro. My thesis work covered
- Numerical study of light in aperiodic plasmonic and photonic crystals.
- Combining top-down and bottom-up fabrication to realize aperiodic plasmonic crystals and nanogalaxies.
- Optical characterization of the fabricated nanostructures as passive optical structures, colorimeteric sensor and surface enhanced raman substrate.
- Studying the ability of aperiodic plasmonic crystals for light extraction.
- Fabrication of periodic and aperiodic photonic crystals of biopolymers.