Welcome to Clarke Lab
Current research topics in the Clarke group include:
- Utilizing the photothermal effect of metal nanoparticles:
Metal nanoparticles embedded in polymer composites can act as remotely-controlled heating elements and be used to manipulate sample properties by "nanoscopic heating from within". Our recent results demonstrate that irradiation with relatively weak light resonant with the nanoparticle's surface plasmon resonance induces dramatic heating in the immediate area of the nanoparticle, while the rest of the material remains largely unaffected.
Recent research accomplishments highlights include:
- Using anisotropically-shaped nanoparticles enables further experimental control via the polarization selectivity of the photothermal effect.
- The photothermal effect can generate thermal processing outcomes unachievable by conventional heating methods.
- Shape memory polymers embedded with nanoparticles are readily actuated using light.
- D. B. Abbott et al., Macromolecular Chemistry and Physics (in press) (2014). (journal) [paper]
- V. Viswanath et al., Macromolecules 46, 8596 (2013). (journal) [paper]
- S. Maity et al., Particle & Particle Systems Characterization 30, 193 (2013). (journal) [paper]
- S. Maity et al., Adv. Funct. Mater. 22, 5259 (2012). (journal) [paper]
- S. Maity et al., Polymer 52, 1674 (2011). (journal) [paper]
Click for some news stories about our earlier results:
Above: Kristen Hale prepares to electrospin.
- Approaches for "scaling up" electrospinning:
Development of electrospinning approaches enabling increased throughput while still generating high-quality nanofibrous materials (i.e. sub-micron fiber diameters with a narrow fiber distribution) represents a critical goal for facilitating broader industrial utilization of these polymeric materials. A host of applications ranging from tissue scaffolding for biomedical applications, as sensors, in air and water filtration systems, or acting as "smart" fabrics would benefit from such capability.
- Towards this end, we have demonstrated that electrospinning from an unconfined fluid near a plate edge produces small diameter fibers with a narrow size distribution, and has remarkable similarity to traditional needle electrospinning approaches while also possessing clear advantages for increased mass throughput.
- This concept has been extended by electrospinning from a stationary, thin-lipped fluid-containing bowl. Our recent paper detailing this experiment has been downloaded >1742 times according to the journal website metrics (link) [as of 09/29/14] since first becoming available online about three years ago [08/01/11].
- Further, by utilizing polymer solutions containing a high concentration of salt, electrospinning can be achieved with virtually no linear region but a vastly increased whipping region, enabling continuous fiber production from parallel jets, with each having an extremely high feed rate -- the combined consequence of is an overall tremendously enhanced nanofiber production rate.
- N. M. Thoppey et al., Polymer (in press) (2014). (journal) [paper]
- M. P. Roman et al., Macromolecules 46, 7352 (2013). (journal) [paper]
- N. M. Thoppey et al., Macromolecules 45, 6527 (2012). (journal) [paper]
- N. M. Thoppey et al., Nanotechnology 22, 345301 (2011). (journal) [paper]
- Muthuraman Thoppey et al., Polymer 51, 4928 (2010). (journal) [paper]
Click for news stories about the unconfined electrospinning technique:
Above: Mary Scott and the ultra high vacuum chamber.
Motional dynamics revealed by dielectric spectroscopy:
Molecular sub-monolayers (uniformly distributed molecules covalently bound to a substrate) enable an alternative approach to study glass transitions because these types of samples manifest different features than other glassy systems such as bulk molecular glasses, glassy polymers, or granular materials.
- Molecular dynamics within sub-monolayer collections of surface-bound alkyl chains (substituted alkylsilanes) can be probed with highly sensitive narrow-band dielectric spectroscopy. In this system, a transition from independent dynamics to glassy motion is observed as the density is increased.
Top: Courtney Evans repairs an old cryostat system.
Observing effects of nanoscale confinement:
The study of electrical percolation within carbon-nanotube polymer composites in complex geometries such as fibrous mats, is undertaken from both computational and experimental perspectives.
- We have identified interesting finite-size effects that are experimentally accessible for carbon-nanotube composites in thin film or fibrous geometries.
Our scientific investigations are innately interdisciplinary and often collaborative with researchers in the NCSU departments of Chemical Engineering, Chemistry, and Textile Engineering, Chemistry, and Science.
Dr. Clarke is an associate professor in the Department of Physics at NC State University, and an adjunct member of the Textiles Engineering, Chemistry and Science Department, as well as of the joint Department of Biomedical Engineering (UNC-CH and NCSU).
Dr. Bochinski is a research assistant professor in the Department of Physics at NC State University.