104 research outputs found
Shape Memory Alloy Micro-Actuator for Handling of Head Gimbal Assembly
This study proposes a methodology to design a shape memory alloy micro-actuator as a new handling device of Head Gimbal Assembly (HGA). The actuator consists of several finger-like Nitinol-and-Polyimide bimorph beams that are able to deflect at high temperature due to thermally induced strain mismatch between these two materials. To design the geometry of micro-actuator, various beam dimensions including lengths, widths and thicknesses are evaluated using ANSYS program. Furthermore, the contact force between micro-actuator and HGA is also studied. The simulation results suggest the feasibility of using the proposed micro-actuator for HGA handling applicatio
IS-16 Innovation on Microfluidics-based Device for Single Cell Analysis, A Canine Cutaneous Mast Cell Tumor Model
Recently, our laboratory, Companion Animal Cancer Research Unit, CAC-RU is interested in cancer stem cell (CSC) analysis both at the single cell and the tissue-based levels. However, cellular heterogeneity is still the major hassle for our comprehension in CSC biology. Therefore, to overcome and eradicate this big obstacles, a single cell analysis method must be established. Our laboratory has finally setup and integrated the microfluidics-based single cell analysis into our CSC researches under the association with Department of Mechanical Engineering, Faculty of Engineering, Chulalongkorn University and Thai Micro-electronic Centre, NECTEC, Ministry of Science and Technology, Thailand and Faculty of Medical Technic, Mahidol University since 2013 till present
Graphene-based photovoltaic cells for near-field thermal energy conversion
Thermophotovoltaic devices are energy-conversion systems generating an
electric current from the thermal photons radiated by a hot body. In far field,
the efficiency of these systems is limited by the thermodynamic
Schockley-Queisser limit corresponding to the case where the source is a black
body. On the other hand, in near field, the heat flux which can be transferred
to a photovoltaic cell can be several orders of magnitude larger because of the
contribution of evanescent photons. This is particularly true when the source
supports surface polaritons. Unfortunately, in the infrared where these systems
operate, the mismatch between the surface-mode frequency and the semiconductor
gap reduces drastically the potential of this technology. Here we show that
graphene-based hybrid photovoltaic cells can significantly enhance the
generated power paving the way to a promising technology for an intensive
production of electricity from waste heat.Comment: 5 pages, 4 figure
Maskless Plasmonic Lithography at 22â nm Resolution
Optical imaging and photolithography promise broad applications in nano-electronics, metrologies, and single-molecule biology. Light diffraction however sets a fundamental limit on optical resolution, and it poses a critical challenge to the down-scaling of nano-scale manufacturing. Surface plasmons have been used to circumvent the diffraction limit as they have shorter wavelengths. However, this approach has a trade-off between resolution and energy efficiency that arises from the substantial momentum mismatch. Here we report a novel multi-stage scheme that is capable of efficiently compressing the optical energy at deep sub-wavelength scales through the progressive coupling of propagating surface plasmons (PSPs) and localized surface plasmons (LSPs). Combining this with airbearing surface technology, we demonstrate a plasmonic lithography with 22â
nm half-pitch resolution at scanning speeds up to 10â
m/s. This low-cost scheme has the potential of higher throughput than current photolithography, and it opens a new approach towards the next generation semiconductor manufacturing
Plasmonic Luneburg and Eaton Lenses
Plasmonics is an interdisciplinary field focusing on the unique properties of
both localized and propagating surface plasmon polaritons (SPPs) -
quasiparticles in which photons are coupled to the quasi-free electrons of
metals. In particular, it allows for confining light in dimensions smaller than
the wavelength of photons in free space, and makes it possible to match the
different length scales associated with photonics and electronics in a single
nanoscale device. Broad applications of plasmonics have been realized including
biological sensing, sub-diffraction-limit imaging, focusing and lithography,
and nano optical circuitry. Plasmonics-based optical elements such as
waveguides, lenses, beam splitters and reflectors have been implemented by
structuring metal surfaces or placing dielectric structures on metals, aiming
to manipulate the two-dimensional surface plasmon waves. However, the abrupt
discontinuities in the material properties or geometries of these elements lead
to increased scattering of SPPs, which significantly reduces the efficiency of
these components. Transformation optics provides an unprecedented approach to
route light at will by spatially varying the optical properties of a material.
Here, motivated by this approach, we use grey-scale lithography to
adiabatically tailor the topology of a dielectric layer adjacent to a metal
surface to demonstrate a plasmonic Luneburg lens that can focus SPPs. We also
realize a plasmonic Eaton lens that can bend SPPs. Since the optical properties
are changed gradually rather than abruptly in these lenses, losses due to
scattering can be significantly reduced in comparison with previously reported
plasmonic elements.Comment: Accepted for publication in Nature Nanotechnolog
Basis and Lattice Polarization Mechanisms for Light Transmission through Nanohole Arrays in a Metal Film
Controlling waves in space and time for imaging and focusing in complex media
In complex media such as white paint and biological tissue, light encounters nanoscale refractive-index inhomogeneities that cause multiple scattering. Such scattering is usually seen as an impediment to focusing and imaging. However, scientists have recently used strongly scattering materials to focus, shape and compress waves by controlling the many degrees of freedom in the incident waves. This was first demonstrated in the acoustic and microwave domains using time reversal, and is now being performed in the optical realm using spatial light modulators to address the many thousands of spatial degrees of freedom of light. This approach is being used to investigate phenomena such as optical super-resolution and the time reversal of light, thus opening many new avenues for imaging and focusing in turbid medi
Resonant terahertz transmission in plasmonic arrays of subwavelength holes
A review of transmission properties of two-dimensional plasmonic structures in the terahertz regime is presented. Resonant terahertz transmission was demonstrated in arrays of subwavelength holes patterned on both metals and semiconductors. The effects of hole shape, hole dimensions, dielectric function of metals, array film thickness, and a dielectric overlayer were investigated by the state-of-the-art terahertz spectroscopy modalities. Extraordinary terahertz transmission was demonstrated in arrays of subwavelength holes made even from Pb, a generally poor metal, and having optically thin thicknesses less than one-third of a skin depth. We also observed a direct transition of a surface plasmon resonance from a photonic crystal minimum in a photo-doped semiconductor array. According to the Fano model, transmission properties of such plasmonic arrays are characterized by two essential contributions: resonant excitation of surface plasmons and nonresonant direct transmission. Plasmonic structures will find fascinating applications in terahertz imaging, biomedical sensing, subwavelength terahertz spectroscopy, and integrated terahertz devices.Peer reviewedElectrical and Computer Engineerin
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