We demonstrate an infrared broadband metasurface absorber that is suitable for increasing the response speed of a microbolometer by reducing its thermal mass. A large fraction of holes are made in a ...periodic pattern on a thin lossy metal layer characterised with a non-dispersive effective surface impedance. This can be used as a non-resonant metasurface that can be integrated with a Salisbury screen absorber to construct an absorbing membrane for a microbolometer that can significantly reduce the thermal mass while maintaining high infrared broadband absorption in the long wavelength infrared (LWIR) band. The non-dispersive effective surface impedance can be matched to the free space by optimising the surface resistance of the thin lossy metal layer depending on the size of the patterned holes by using a dc approximation method. In experiments a high broadband absorption was maintained even when the fill factor of the absorbing area was reduced to 28% (hole area: 72%), and it was theoretically maintained even when the fill factor of the absorbing area was reduced to 19% (hole area: 81%). Therefore, a metasurface with a non-dispersive effective surface impedance is a promising solution for reducing the thermal mass of infrared microbolometer pixels.
Single-molecule studies of protein–DNA interactions have shed critical insights into the molecular mechanisms of nearly every aspect of DNA metabolism. The development of DNA curtainsa method for ...organizing arrays of DNA molecules on a fluid lipid bilayerhas greatly facilitated these studies by increasing the number of reactions that can be observed in a single experiment. However, the utility of DNA curtains is limited by the challenges associated with depositing nanometer-scale lipid diffusion barriers onto quartz microscope slides. Here, we describe a UV lithography-based method for large-scale fabrication of chromium (Cr) features and organization of DNA molecules at these features for high-throughput single-molecule studies. We demonstrate this approach by assembling 792 independent DNA arrays (containing >900 000 DNA molecules) within a single microfluidic flowcell. As a first proof of principle, we track the diffusion of Mlh1-Mlh3a heterodimeric complex that participates in DNA mismatch repair and meiotic recombination. To further highlight the utility of this approach, we demonstrate a two-lane flowcell that facilitates concurrent experiments on different DNA substrates. Our technique greatly reduces the challenges associated with assembling DNA curtains and paves the way for the rapid acquisition of large statistical data sets from individual single-molecule experiments.
We report on time-frequency analysis (TFA) of dispersion in a 1-D magneto-inductive waveguide (MIW). The short-time Fourier transform (STFT) and Wigner-Ville distribution (WVD) are used to localize ...the frequency content of the dispersed wave as a function of time and to estimate the group velocity in experiments using a 1-D MIW constructed with planar resonators. Time-domain reflectometry (TDR) measurements are performed after deliberately introducing defects along the waveguide; and the results are analyzed with TFA, demonstrating the potential for using such MIW-TDR configurations as sensors. The WVD-TFA is shown to provide precise time-frequency information, accurate defect localization, and group velocity estimation, confirming the slow wave long-range nature of dispersive MIWs. The adaptability of the MIW-TDR setup and the accuracy of the WVD for localization make the technique a suitable candidate for sensing applications using engineered dispersive media.
A wavelength-selective metasurface absorber suitable for use in multispectral microbolometer focal plane arrays in the long-wavelength infrared (LWIR) region is theoretically and experimentally ...investigated. We show that a thin metal metasurface, which is characterized by effective surface impedance, as an absorbing layer can be integrated with an asymmetric Fabry-Pérot cavity to construct a wavelength-selective perfect absorber. The absorbed infrared energy is mainly dissipated in a thin metal metasurface, in contrast to a multilayer metamaterial absorber. The calculated and experimental spectral responses of the metasurface absorbers show excellent wavelength-selective narrowband absorption to allow multispectral imaging in LWIR.
Aptamer biosensors have been immobilized on beads, introduced into micromachined chips on the electronic tongue sensor array, and used for the detection and quantitation of proteins. Aptamer chips ...could detect proteins in both capture and sandwich assay formats. Unlike most protein-based arrays, the aptamer chips could be stripped and reused multiple times. The aptamer chips proved to be useful for screening aptamers from in vitro selection experiments and for sensitively quantitating the biothreat agent ricin.
The development of a chip-based sensor array composed of individually addressable agarose microbeads has been demonstrated for the rapid detection of DNA oligonucleotides. Here, a “plug and play” ...approach allows for the simple incorporation of various biotinylated DNA capture probes into the bead-microreactors, which are derivatized in each case with avidin docking sites. The DNA capture probe containing microbeads are selectively arranged in micromachined cavities localized on silicon wafers. The microcavities possess trans-wafer openings, which allow for both fluid flow through the microreactors/analysis chambers and optical access to the chemically sensitive microbeads. Collectively, these features allow the identification and quantitation of target DNA analytes to occur in near real time using fluorescence changes that accompany binding of the target sample. The unique three-dimensional microenvironment within the agarose bead and the microfluidics capabilities of the chip structure afford a fully integrated package that fosters rapid analyses of solutions containing complex mixtures of DNA oligomers. These analyses can be completed at room temperature through the use of appropriate hybridization buffers. For applications requiring analysis of ≤102 different DNA sequences, the hybridization times and point mutation selectivity factors exhibited by this bead array method exceed in many respects the operational characteristics of the commonly utilized planar DNA chip technologies. The power and utility of this microbead array DNA detection methodology is demonstrated here for the analysis of fluids containing a variety of similar 18-base oligonucleotides. Hybridization times on the order of minutes with point mutation selectivity factors greater than 10 000 and limit of detection values of ∼10-13 M are obtained readily with this microbead array system.
A pair of new polymers, poly(di-t-butylacenaphthylene) (pTBAcN) and poly(dipropylacenaphthylene) (pPAcN), were made via Friedel–Crafts alkylation of polyacenaphthylene. These polymers exhibit ...thermal stability beyond 250 °C and solubility in excess of 25 wt % in aliphatic hydrocarbons. Films of pPAcN over 10 μm thick were successively applied to planar surfaces via brush coating. Chemical memory for a passive wire resonant sensor was utilized to detect aliphatic hydrocarbons in high temperature environments. The coated threshold sensor showed a lower, stable resonant frequency before and after exposure to water at 130 °C for 3 h and showed an increased triggered resonant frequency after aliphatic exposure, consistent with an uncoated sensor device.
As the focus of applied research in topological insulators (TI) evolves, the need to synthesize large-area TI films for practical device applications takes center stage. However, constructing ...scalable and adaptable processes for high-quality TI compounds remains a challenge. To this end, a versatile van der Waals epitaxy (vdWE) process for custom-feature bismuth telluro-sulfide TI growth and fabrication is presented, achieved through selective-area fluorination and modification of surface free-energy on mica. The TI features grow epitaxially in large single-crystal trigonal domains, exhibiting armchair or zigzag crystalline edges highly oriented with the underlying mica lattice and only two preferred domain orientations mirrored at 180°. As-grown feature thickness dependence on lateral dimensions and denuded zones at boundaries are observed, as explained by a semiempirical two-species surface migration model with robust estimates of growth parameters and elucidating the role of selective-area surface modification. Topological surface states contribute up to 60% of device conductance at room temperature, indicating excellent electronic quality. High-yield microfabrication and the adaptable vdWE growth mechanism with readily alterable precursor and substrate combinations lend the process versatility to realize crystalline TI synthesis in arbitrary shapes and arrays suitable for facile integration with processes ranging from rapid prototyping to scalable manufacturing.
The development of a chip-based sensor array composed of individually addressable polystyrene−poly(ethylene glycol) and agarose microspheres has been demonstrated. The microspheres are selectively ...arranged in micromachined cavities localized on silicon wafers. These cavities are created with an anisotropic etch and serve as miniaturized reaction vessels and analysis chambers. A single drop of fluid provides sufficient analysis media to complete ∼100 assays in these microetch pits. The cavities possess pyramidal pit shapes with trans-wafer openings that allows for both fluid flow through the microreactors/analysis chambers and optical access to the chemically sensitive microspheres. Identification and quantitation of analytes occurs via colorimetric and fluorescence changes to receptor and indicator molecules that are covalently attached to termination sites on the polymeric microspheres. Spectral data are extracted from the array efficiently using a charge-coupled device allowing for the near-real-time digital analysis of complex fluids. The power and utility of this new microbead array detection methodology is demonstrated here for the analysis of complex fluids containing a variety of important classes of analytes including acids, bases, metal cations, metabolic cofactors, and antibody reagents.
The development of a micromachined fluidic structure for the introduction of liquid samples into a chip-based sensor array composed of individually addressable polymeric microbeads is presented. The ...micromachined structure consists of micromachined storage cavities combined with a covering glass layer that confines the microbeads and fluidic channels. In our sensor array transduction occurs via optical (colorimetric and fluorescence) changes to receptors and indicator molecules that are covalently attached to termination sites on the polymeric microbeads. Spectral data are acquired for each of the individual microbeads using a charged-coupled device (CCD) allowing for the near-real-time analysis of liquid sample. Hence the micromachined fluidic structure must allow for both optical access to the microbeads and fluid flow through the micromachined cavities that serve as the microreactors/analysis chambers. One of the key parts of the structure is a passive fluid introduction system driven only by capillary force. This simple means of fluid introduction realizes a compact device. The capillary flow on the inlet channel has been studied, and the responses of the microbeads (alizarin complexone) to a liquid sample have been characterized. The test results show that this system is useful in a micro-total-analysis-system (μ-TAS) and biomedical applications.
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