Mechanics and Photonics with 2D Materials
Mechanically Reconfigurable Plasmonics based on Nanostructured Graphene
Mechanically tunable light absorption wavelength with wrinkled graphene structures. A schematic illustration of the uniaxially wrinkled graphene structure (left panel) showing a reversible mechanical change of the wrinkled structure. Optical absorption spectra (right panel) for the wrinkled graphene structures with various aspect ratio of wrinkle height (h) to wavelength (λc)
Journal Paper: Mechanically Reconfigurable Architectured Graphene for Tunable Plasmonic Resonances
Pilgyu Kang, Kyoung-Ho Kim, Hong-Gyu Park and SungWoo Nam, Light: Science & Applications 17 (2018)
Crumpled Graphene Photodetector with Enhanced, Strain-Tunable, and Wavelength-Selective Photoresponsivity
A stretchable photodetector with enhanced, strain-tunable photoresponsivity is developed based on crumpled graphene by engineering 2D graphene into 3D structures. This crumpled graphene photodetector demonstrates ≈400% enhanced photoresponsivity led by an order-of-magnitude enhanced extinction of graphene and 100% modulation in photoresponsivity with 200% applied strain. Finally, strain-tunable, wavelength-selective photodetection is shown by integrated colloidal photonic crystals–crumpled graphene photodetector devices.
Journal Paper: Adv. Mater. 2016, DOI: 10.1002/adma.201600482
Ultrasensitive Molecular Sensing using a Nanophotonic Tweezer (Sci. Rep., 2015, 5:12087)
A novel optofluidic biosensing method using a nanotweezer is presented, allowing a simple and rapid biological assay. Optical biosensing methods have provided necessities that biosensors are required to perform, such as high sensitivity and specificity with a price. The methodology we developed relys on an optical trap and an observation with the trap stiffness. The optical trap is exploited to observe a change of the trap stiffness, which is sensitive to the change of the size of an optically trapped particle caused by bindings of target biomolecules to the trapped particle.
Angular Orientation of Nanorods using Nanophotonic Tweezers
Near-field optical techniques have enabled trapping, transport, and handling of nanoscopic materials much smaller than what can be manipulated with traditional optical tweezers. Here we extend the scope of what is possible by demonstrating angular orientation and rotational control of both biological and non-biological nanoscale rods using photonic crystal nanotweezers. In our experiments, single microtubules (diameter 25 nm, length 8 μm) and multi-walled carbon nanotubes (outer diameter 110 – 170 nm, length 5 μm) are rotated by the optical torque resulting from their interaction with the evanescent field emanating from these devices. An angular trap stiffness of k = 92.8 pN·nm/rad2-mW is demonstrated for the microtubules and a torsional spring constant of 22.8 pN nm/rad2-mW is measured for the nanotubes. We expect that this new capability will facilitate the development of high precision nanoassembly schemes and biophysical studies of bending strains of biomolecules.
Journal Paper: Nano Lett., 2012, 12 (12), pp 6400–6407
High Resolution Reversible Color Images on Photonic Crystal Substrate
When light is incident on a crystalline structure with appropriate periodicity, some colors will be preferentially reflected (Joannopoulos, J. D.; Meade, R. D.; Winn, J. N. Photonic crystals : molding the flow of light; Princeton University Press: Princeton, NJ, 1995; p ix, 137 pp). These photonic crystals and the structural color they generate represent an interesting method for creating reflective displays and drawing devices, since they can achieve a continuous color response and do not require back lighting (Joannopoulos, J. D.; Villeneuve, P. R.; Fan, S. H. Photonic crystals: Putting a new twist on light. Nature1997, 386, 143–149; Graham-Rowe, D. Tunable structural colour. Nat. Photonics2009, 3, 551–553.; Arsenault, A. C.; Puzzo, D. P.; Manners, I.; Ozin, G. A. Photonic-crystal full-colour displays. Nat. Photonics2007, 1, 468–472; Walish, J. J.; Kang, Y.; Mickiewicz, R. A.; Thomas, E. L. Bioinspired Electrochemically Tunable Block Copolymer Full Color Pixels. Adv. Mater.2009, 21, 3078). Here we demonstrate a technique for creating erasable, high-resolution, color images using otherwise transparent inks on self-assembled photonic crystal substrates (Fudouzi, H.; Xia, Y. N. Colloidal crystals with tunable colors and their use as photonic papers.Langmuir2003, 19, 9653–9660). Using inkjet printing, we show the ability to infuse fine droplets of silicone oils into the crystal, locally swelling it and changing the reflected color (Sirringhaus, H.; Kawase, T.; Friend, R. H.; Shimoda, T.; Inbasekaran, M.; Wu, W.; Woo, E. P. High-resolution inkjet printing of all-polymer transistor circuits. Science2000, 290, 2123–2126). Multicolor images with resolutions as high as 200 μm are obtained from oils of different molecular weights with the lighter oils being able to penetrate deeper, yielding larger red shifts. Erasing of images is done simply by adding a low vapor pressure oil which dissolves the image, returning the substrate to its original state.
Journal Paper: Langmuir, 2011, 27 (16), pp 9676–9680