Person: Khan, Mughees
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Khan
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Mughees
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Khan, Mughees
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Publication Buckling-Induced Reversible Symmetry Breaking and Amplification of Chirality Using Supported Cellular Structures(Wiley, 2013) Kang, Sung Hoon; Shan, Sicong; Noorduin, Wim L.; Khan, Mughees; Aizenberg, Joanna; Bertoldi, KatiaBuckling‐induced reversible symmetry breaking and amplification of chirality using macro‐ and microscale supported cellular structures is described. Guided by extensive theoretical analysis, cellular structures are rationally designed, in which buckling induces a reversible switching between achiral and chiral configurations. Additionally, it is demonstrated that the proposed mechanism can be generalized over a wide range of length scales, geometries, materials, and stimuli.Publication Structural Transformation by Electrodeposition on Patterned Substrates (STEPS): A New Versatile Nanofabrication Method(American Chemical Society (ACS), 2012) Kim, Philseok; Epstein, Alexander K; Khan, Mughees; Zarzar, Lauren; Lipomi, Darren J.; Whitesides, George; Aizenberg, JoannaArrays of high-aspect-ratio (HAR) nano- and microstructures are of great interest for designing surfaces for applications in optics, bio−nano interfaces, microelectromechanical systems, and microfluidics, but the difficulty of systematically and conveniently varying the geometries of these structures significantly limits their design and optimization for a specific function. This paper demonstrates a low-cost, high-throughput benchtop method that enables a HAR array to be reshaped with nanoscale precision by electrodeposition of conductive polymers. The method—named STEPS (structural transformation by electrodeposition on patterned substrates)—makes it possible to create patterns with proportionally increasing size of original features, to convert isolated HAR features into a closed-cell substrate with a continuous HAR wall, and to transform a simple parent two-dimensional HAR array into new three-dimensional patterned structures with tapered, tilted, anisotropic, or overhanging geometries by controlling the deposition conditions. We demonstrate the fabrication of substrates with continuous or discrete gradients of nanostructure features, as well as libraries of various patterns, starting from a single master structure. By providing exemplary applications in plasmonics, bacterial patterning, and formation of mechanically reinforced structures, we show that STEPS enables a wide range of studies of the effect of substrate topography on surface properties leading to optimization of the structures for a specific application. This research identifies solution-based deposition of conductive polymers as a new tool in nanofabrication and allows access to 3D architectures that were previously difficult to fabricate.Publication Bioinspired micrograting arrays mimicking the reverse color diffraction elements evolved by the butterfly Pierella luna(Proceedings of the National Academy of Sciences, 2014) England, Grant Tyler; Kolle, Mathias; Kim, Philseok; Khan, Mughees; Camayd-Munoz, Phil; Mazur, Eric; Aizenberg, JoannaRecently, diffraction elements that reverse the color sequence normally observed in planar diffraction gratings have been found in the wing scales of the butterfly Pierella luna. Here, we describe the creation of an artificial photonic material mimicking this reverse color-order diffraction effect. The bioinspired system consists of ordered arrays of vertically oriented microdiffraction gratings. We present a detailed analysis and modeling of the coupling of diffraction resulting from individual structural components and demonstrate its strong dependence on the orientation of the individual miniature gratings. This photonic material could provide a basis for novel developments in biosensing, anticounterfeiting, and efficient light management in photovoltaic systems and light-emitting diodes.Publication Liquid-based gating mechanism with tunable multiphase selectivity and antifouling behaviour(Nature Publishing Group, 2015) Hou, Xu; Hu, Yuhang; Grinthal, Alison; Khan, Mughees; Aizenberg, JoannaLiving organisms make extensive use of micro- and nanometre-sized pores as gatekeepers for controlling the movement of fluids, vapours and solids between complex environments. The ability of such pores to coordinate multiphase transport, in a highly selective and subtly triggered fashion and without clogging, has inspired interest in synthetic gated pores for applications ranging from fluid processing to 3D printing and lab-on-chip systems. But although specific gating and transport behaviours have been realized by precisely tailoring pore surface chemistries and pore geometries a single system capable of controlling complex, selective multiphase transport has remained a distant prospect, and fouling is nearly inevitable. Here we introduce a gating mechanism that uses a capillary-stabilized liquid as a reversible, reconfigurable gate that fills and seals pores in the closed state, and creates a non-fouling, liquid-lined pore in the open state. Theoretical modelling and experiments demonstrate that for each transport substance, the gating threshold—the pressure needed to open the pores—can be rationally tuned over a wide pressure range. This enables us to realize in one system differential response profiles for a variety of liquids and gases, even letting liquids flow through the pore while preventing gas from escaping. These capabilities allow us to dynamically modulate gas–liquid sorting in a microfluidic flow and to separate a three-phase air–water–oil mixture, with the liquid lining ensuring sustained antifouling behaviour. Because the liquid gating strategy enables efficient long-term operation and can be applied to a variety of pore structures and membrane materials, and to micro- as well as macroscale fluid systems, we expect it to prove useful in a wide range of applications.Publication Enhanced Single-Photon Emission from a Diamond-Silver Aperture(Nature Publishing Group, 2011) Choy, Jennifer Tze-Heng; Hausmann, Birgit Judith Maria; Babinec, Thomas Michael; Bulu, Irfan; Khan, Mughees; Maletinsky, Patrick; Yacoby, Amir; Lončar, MarkoSolid-state quantum emitters, such as the nitrogen-vacancy centre in diamond, are robust systems for practical realizations of various quantum information processing protocols and nanoscale magnetometry schemes at room temperature. Such applications benefit from the high emission efficiency and flux of single photons, which can be achieved by engineering the electromagnetic environment of the emitter. One attractive approach is based on plasmonic resonators, in which sub-wavelength confinement of optical fields can strongly modify the spontaneous emission of a suitably embedded dipole despite having only modest quality factors. Meanwhile, the scalability of solid-state quantum systems critically depends on the ability to control such emitter–cavity interaction in a number of devices arranged in parallel. Here, we demonstrate a method to enhance the radiative emission rate of single nitrogen-vacancy centres in ordered arrays of plasmonic apertures that promises greater scalability over the previously demonstrated bottom-up approaches for the realization of on-chip quantum networks.