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Long-wave infrared (LWIR, 6–14 µm) processes enormous potential for chem/biosensing as it covers abundant molecular absorption fingerprints. Waveguides provide an attractive chip-scale miniaturization solution for optical sensors. However, the exploration of waveguide sensors in this wavelength range is limited. Here, an LWIR photonic platform for fast and sensitive on-chip gas sensing is developed using suspended silicon (Si) waveguide supported by subwavelength grating (SWG) metamaterial claddings. This platform provides a viable approach to fully exploit the transparency window of Si. The SWG structure provides a promising solution to engineer the mode profile for strong light–analyte interaction. Propagation loss and bending loss are studied in the broad wavelength range of 6.4–6.8 µm. Functional devices including grating couplers, Y-junctions, and directional couplers are also demonstrated with high performance. Sensing demonstration based on our platform is presented using toluene vapor detection as an example. The corresponding limit of detection reaches 75 ppm. The response and recovery time to 75 ppm toluene are about 0.8 and 3.4 s, respectively. This good performance makes our platform a promising candidate for on-site medical and environmental applications.

Background Postherpetic neuralgia (PHN) is the most common complication of acute herpes zoster. The treatment of PHN remains a challenge for clinical pain management. Despite the effectiveness of anticonvulsants, antidepressants, and lidocaine patches in reducing PHN, many patients still face intractable pain disorders. In this randomized controlled study, we evaluated whether hydromorphone through intravenous patient-controlled analgesia (IV PCA) was effective in relieving PHN. Methods Patients with PHN were randomly divided into two groups, one group received oral pregabalin with IV normal saline, another group received oral pregabalin with additional IV PCA hydromorphone for two weeks. Efficacy was evaluated at 1, 4, and 12 weeks after the end of the treatments. Results Two hundred and one patients were followed up for 12 weeks. After treatment, numerical rating scale (NRS) score of patients in the hydromorphone group was significantly lower than that of the control group, and the difference of NRS scores between the two groups was statistically significant at 4 and 12 weeks after treatment. The frequency of breakthrough pain in the hydromorphone group was significantly lower than that in the control group 1 and 4 weeks after treatment. After treatment, the quality of sleep in the hydromorphone group was significantly improved compared with the control group. The most common adverse reactions in the hydromorphone group were dizziness and nausea, with no significant respiratory depression. Conclusions IV PCA hydromorphone combined with oral pregabalin provides superior pain relief in patients with PHN, which is worthy of clinical application and promotion.

Metamaterials, consisting of subwavelength resonant structures, can be artificially engineered to yield desired response to electromagnetic waves. In contrast to the naturally existing materials whose properties are limited by their chemical compositions and structures, the optical response of metamaterials is controlled by the geometrics of resonant unit cells, called “meta-atoms”. Many exotic functionalities such as negative refractive index, cloaking, perfect absorber, have been realized in metamaterials. One recent technical advance in this field is the active metamaterial, in which the structure of metamaterials can be tuned to realize multiple states in a single device. Microelectromechanical systems (MEMS) technology, well-known for its ability of reconfiguring mechanical structures, complementary metal-oxide-semiconductor (CMOS) compatibility and low power consumption, is perfectly suitable for such purpose. In the past one decade, we have seen numerous exciting works endeavoring to incorporate the novel MEMS functionalities with metamaterials for widespread applications. In this review, we will first visit the fundamental theories of MEMS-based active metamaterials, such as the lumped circuit model, coupled-mode theory, and interference theory. Then, we summarize the recent applications of MEMS-based metamaterials in various research fields. Finally, we provide an outlook on the future research directions of MEMS-based metamaterials and their possible applications.

Miniaturized infrared spectroscopy is highly desired for widespread applications, including environment monitoring, chemical analysis, and biosensing. Nanoantennas, as a promising approach, feature strong field enhancement and provide opportunities for ultrasensitive molecule detection even in the nanoscale range. However, current efforts for higher sensitivities by nanogaps usually suffer a trade-off between the performance and fabrication cost. Here, novel crooked nanoantennas are designed with a different paradigm based on loss engineering to overcome the above bottleneck. Compared to the commonly used straight nanoantennas, the crooked nanoantennas feature higher sensitivity and a better fabrication tolerance. Molecule signals are increased by 25 times, reaching an experimental enhancement factor of 2.8 × 104. The optimized structure enables a transmissive CO2 sensor with sensitivities up to 0.067% ppm-1. More importantly, such a performance is achieved without sub-100 nm structures, which are common in previous works, enabling compatibility with commercial optical lithography. The mechanism of our design can be explained by the interplay of radiative and absorptive losses of nanoantennas that obeys the coupled-mode theory. Leveraging the advantage of the transmission mode in an optical system, our work paves the way toward cheap, compact, and ultrasensitive infrared spectroscopy.

Ovarian cancer is predominant form of malignant which occupies 70 % cancer in women worldwide. Taxals, anthrocyclins and platinum based drugs are used as chemotherapeutic for treatment of ovarian cancer. These drugs were limited by drug resistance and it produces several toxicity. Therefore, we used natural drug which inhibits the cancer cell growth by modulating specific molecular mechanisms. This study, we evaluated the 6-shogaol a active component from ginger inhibits cell proliferation by modulation of JAK/STAT-3 signalling in ovarian cancer cell lines (A2780). In this study, we found that 6-shogaol induces cytotoxicity, ROS production and apoptosis in A2780 cell lines by time depending manner. Moreover, signal transducer and activating transcription-3 (STAT-3) has been consider as novel transcriptional factor which regulates apoptosis, cell proliferation and angiogensis. Inhibition of STAT-3 transcription considered as novel strategy to inhibiting ovarian cell growth. In this study, we found that 6-shogaol inhibits STAT-3 translocation there by inhibits the over expression of PCNA, cyclin-D1, Bcl-2 and decreased expression of Bax, caspase-9 and 3 in A2780 cell lines. This results concluded that 6-shogaol inhibits ovarian cell growth and induces apoptosis through inhibits the translocation STAT-3.

The integration of waveguides and photodetectors is an indispensable step toward the realization of on-chip spectroscopic sensing systems. However, the development of waveguide-integrated photodetectors in the attractive long-wave infrared (LWIR) range faces challenges from both waveguide platforms due to the bottom cladding material absorption and photodetection technologies due to the low LWIR photon energy. Here, we demonstrate an LWIR waveguide-integrated photodetector through heterogeneous integration of graphene photodetector and Si waveguide on CaF 2 substrate. A high-yield transfer printing method is developed for flexibly integrating waveguide and substrate materials to solve the bottom cladding material absorption issue. The fabricated Si-on-CaF 2 waveguides show low losses in the broad LWIR wavelength range of $6.3-7.1\ \mu\mathrm{m}$ . The graphene photodetector achieves a broadband responsivity of ∼8 mA/W in these low-photon-energy LWIR wavelengths under zero-bias operation with the help of waveguide integration and plasmonic enhancement. Our strategy opens up the possibility for chip-scale, low-cost, and low-power-consumption LWIR spectroscopic sensing systems.

Miniaturized optical spectrometer in the mid-infrared range could open numerous opportunities for widespread applications including environmental monitoring and biosensing. A recent scientific advance in this field is the computational spectrometer based on the wavelength reconstruction method, which features an ultracompact footprint. However, the existing techniques still need multiple pixel arrays which inevitably increases the device complexity and footprint. Here, we demonstrate a transfer-printed nanoelectromechanical Fabry-Perot filter with electrical configurability, implementing a single-pixel computational spectrometer. The tunable wavelength of our filter spans from 5.61 to $4.13\ \mu \mathrm{m}$ with drive voltages from 0 V to 70 V. As a proof of concept, our device can successfully reconstruct the absorption peak of CO 2 at $4.26 \mu\mathrm{m}$ wavelength. Our work lends the function of configurability to emerging computational spectrometers, highlighting the promising potential of this technology.

This paper reports a waveguide-integrated bigradient dielectric metalens with a footprint of only 16.8×10 µm2. In mid-infrared wavelengths of 3.65-3.8 um, the metalens achieves high-efficiency in-plane focusing with the highest ratio of wavelength to focal length/spot size (0.268 & 2.83). After subsequent optimization and design, the total area of the bigradient metalens has been further compressed to 55.1% and demonstrated mode conversion applications and beam steering. This provides focusing components for the next generation of mid-infrared photonic integration, which also holds the potential for spectroscopic sensing, communication, neuromorphic computing, and non-linear optics.

Mid-infrared absorption spectroscopy plays an important role in molecule identification and quantification for widespread applications. Integrated photonics provides opportunities to perform spectroscopic sensing on-chip for the minimization of device size, cost, and power consumption. The integration of waveguides and photodetectors is an indispensable step toward the realization of these on-chip sensing systems. It is desired to extend the operating wavelengths of these on-chip sensing systems to the long-wave infrared (LWIR) range to utilize more molecular absorption fingerprints. However, the development of LWIR waveguide-integrated photodetectors faces challenges from both waveguide platforms due to the bottom cladding material absorption and photodetection technologies due to the low LWIR photon energy. Here, we demonstrate LWIR waveguide-integrated photodetectors through heterogeneous integration of graphene photodetectors and Si waveguides on CaF2 substrates. A high-yield transfer printing method is developed for flexibly integrating the waveguide and substrate materials to solve the bottom cladding material absorption issue. The fabricated Si-on-CaF2 waveguides show low losses in the broad LWIR wavelength range of 6.3-7.1 μm. The graphene photodetector achieves a broadband responsivity of ∼8 mA/W in these low-photon-energy LWIR wavelengths under zero-bias operation with the help of waveguide integration and plasmonic enhancement. We further integrate the graphene photodetector with a Si-on-CaF2 folded waveguide and demonstrate on-chip absorption sensing using toluene as an example. These results reveal the potential of our technology for the realization of chip-scale, low-cost, and low-power-consumption LWIR spectroscopic sensing systems.

Many volatile organic compounds (VOCs) are regarded as major indoor pollutants and potentially threaten human health in the short- and long-term. Several VOCs are also indicators for specific diseases. Thus, portable and selective detection of VOCs is highly desired. In this letter, a chip-scale subwavelength-engineered suspended silicon waveguide platform working in the long-wave infrared is demonstrated for toluene vapor detection. The broadband characterization of this platform is presented and a flat transmission spectrum over the measured wavelength range is shown. With 3.8 dB/cm propagation loss achieved at the toluene absorption fingerprint of 6.65 µm, the limit of detection of toluene sensing reaches 6 ppm. The response and recovery time to the 6 ppm toluene are 3.0 and 5.6 s, respectively. This chip-scale optical gas sensing platform is a promising candidate for on-site real-time environmental monitoring and medical diagnosis.

Vernier effect has been captivated as a promising approach to achieve high-performance photonic sensors. However, experimental demonstration of such sensors in mid-infrared (MIR) range, which covers abundant absorption fingerprints of molecules, is still lacking. Here, we report Vernier effect-based thermally tunable photonic sensors using cascaded ring resonators fabricated on the silicon-on-insulator (SOI) platform. The radii and the coupling gaps in two rings are investigated as key design parameters. By applying organic liquids on our device, we observe an envelope shift of 48 nm with a sensitivity of 3000 nm/RIU and an intensity drop of 6.7 dB. Besides, our device can be thermally tuned with a sensitivity of 0.091 nm/mW. Leveraging the characteristic molecular absorption in the MIR, our work offers new possibilities for complex index sensing, which has wide applications in on-chip photonic sensors.

The design, fabrication, and characterization of 1-D grating waveguide as slow light structure working in mid-infrared (MIR) region are demonstrated for the first time. The effects of various structural parameters on slow light properties are investigated through theoretical analysis, simulation and experimental verification, providing guidance on slow light engineering in 1-D grating waveguide. By adjusting structural parameters, average group indices of 9.4–15.5 with bandwidths of 23–66 nm and normalized delay-bandwidth products of 0.093–0.164 are obtained. Thermo-optic tuning is also demonstrated with π phase shift and group index tuning from 23 to 33 at the wavelength of 3.9024 μm by applying 1.4 mA current. The proposed tunable 1-D grating slow light waveguide provides a promising platform for various MIR applications such as on-chip absorption-based biochemical sensors, tunable optical buffers, and thermo-optic modulators.

The surface-enhanced infrared absorption (SEIRA) technique has been focusing on the metallic resonator structures for decades, exploring different approaches to enhance sensitivity. Although the high enhancement is achieved, the dissipative loss and strong heating are the intrinsic drawbacks of metals. Recently, the dielectric platform has emerged as a promising alternative. In this work, we report a guided resonance-based all-dielectric photonic crystal slab as the platform for SEIRA. The guided resonance-induced enhancement in the effective path length and electric field, together with gas enrichment polymer coating, leads to a detection limit of 20 ppm in carbon dioxide (CO2) sensing. This work explores the feasibility to apply low loss all-dielectric structures as a surface enhancement method in the transmission mode.

Miniaturized optical spectrometers have been realized by exploiting conventional working principles and advanced nanofabrication technology. Especially in the mid-infrared (MIR) range, chip-scale optical spectrometers enable fast and on-site detection of molecular fingerprints for selective chemical sensing in healthcare and environmental monitoring. This miniaturization is also highly desirable for the wearable devices where the tiny functional parts remain on rigid substrates but the electronics are flexible. In the last decade, the triboelectric nanogenerator (TENG) technology has been proven as an indispensable and enabling technology for wearable self-powered sensors, energy harvesters and voltage sources, etc. Although a few TENG based gas sensors have been demonstrated, each of these sensors can detect a particular gas other than diversified gases. Infrared spectrometer is known as an instrument which can investigate the infrared absorption characteristics of gas molecules. It is the best generic technology to sense multiple gases on the same instrument, or device. In this study, we demonstrate a TENG enabled tunable Fabry-Perot (FP) photonic-crystal-slab filter aiming for the computational spectrometer in the MIR range. The textile-triboelectric nanogenerator (T-TENG) provides high open-circuit voltage to shift the resonance wavelengths of the electrostatically actuated FP-filter, where this feature provides the sampling bases required for the computational spectrometer. Furthermore, the FP-filter is fabricated by a new transfer-printing method and shows a large wavelength tunability. As a proof of concept, the transmission spectrum of acetone vapor is reconstructed from 5 to 6.5 µm using this TENG enabled FP-filter. The molecular fingerprint of acetone is identified at 5.75 µm. This work paves the way towards the wearable MIR miniaturized optical spectrometer.

Accurate state of charge estimation of lithium-ion battery is directly related to the safe operation of electric vehicles and also an indispensable function of the battery management system. Four aspects of efforts are made to improve the estimation accuracy. First, for overcoming the drawbacks of equivalent circuit model and electrochemical model, the fractional order impedance model is built via electrochemical impedance spectroscopy data and the fractional element is used to describe the polarization effect in a simple and meaningful way. Second, the discrete state-space equations of the impedance model are inferred by Grunwald-Letnikov definition and parameters of the model including the order of the fractional element are identified together by genetic algorithm (GA) and the experiment data of the dynamic driving cycles. Third, the fractional order unscented Kalman filter technique is presented and the ‘short memory’ technique is employed to improve the computation efficiency of fractional operator. Lastly, experimental validation is implemented to verify the effectiveness of the proposed approach and results show that the SoC estimation accuracy can be improved by the proposed model and estimation method. The estimation error can be controlled within the range of 3%.

Inward migration of cerebellar granule cells (CGCs) after birth is critical for lamination in the cerebellar cortex. N-methyl-d-aspartate (NMDA) subtype of glutamate receptor (NMDAR) tethering CGCs into Bergmann glial fibers mediates the inward movement during the glial-dependent migratory phase. Activation of NMDAR depends on simultaneous binding of the GluN2 subunit by glutamate, and of the GluN1 subunit by d-serine or glycine; d-serine is believed to be an endogenous ligand of NMDAR. We hypothesized that lamination of the cerebellar cortex may be compromised in Srr (the gene for serine racemase (SR)) mutated mice (Srrnull) because of significantly low levels of d-serine per se. Indeed, the external germinal cell layer (EGL) in Srrnull was thicker than in sibling wild-type (WT) mice on postnatal day7 (P7), which accords with decreased CGC migration in Srrnull mice. However, the cerebellar laminar structure in Srrnull mice was normal on P12 and later. Feeding d-serine to pregnant mice abrogated the increased EGL thickness in Srrnull mice on P7. To determine the underlying mechanism of abnormal laminar structure during cerebellar development in Srrnull mice, we examined NMDAR subunits and their ligands. We found increased GluN2B on P10 and increased glycine during P7-12 in the cerebellar homogenates from Srrnull mice compared with the corresponding values from sibling WT mice. In summary, the study revealed how the potential defect in early cerebellar development caused by Srr mutation is circumvented by a compensatory mechanism. This knowledge advances understanding of the adaptation of cerebellar development under the condition of Srr mutation.

Black phosphorus (BP) holds great promise for mid-infrared (MIR) photodetection on waveguide due to its narrow direct bandgap and layered lattice structure. Recently, the first MIR waveguide-integrated BP photodetector was demonstrated through integration with an $80\ \mu \mathrm{m}$ long grating coupler. The relative long device length still falls behind the miniaturization requirement set by compact on-chip MIR sensing systems. Here, we present a method to miniaturize the waveguide-integrated BP photodetector by utilizing slow light effect. The BP photodetector is integrated on a photonic crystal waveguide with only $10\ \mu \mathrm{m}$ length. At a wavelength of $3.825\ \mu \mathrm{m}$ with a group index of 103.3, more than fivefold enhancement of responsivity is achieved, leading to a responsivity of 0.098 A/W under a bias of 0.5 V and an excitation power of $126.9\ \mu \mathrm{W}$ . In comparison with the previous work, comparable responsivity is achieved with one-eighth of the device length.

A deterministic design method and experimental demonstration of single photonic crystal nanocavity supporting both air and dielectric modes in the mid-infrared wavelength region are reported here. The coexistence of both modes is realized by a proper design of photonic dispersion to confine air and dielectric bands simultaneously. By adding central mirrors to make the resonance modes be confined at the bandgap edges, high experimental Q-factors of 2.32 × 104 and 1.59 × 104 are achieved at the resonance wavelength of about 3.875μm and 3.728μm for fundamental dielectric and air modes, respectively. Moreover, multiple sets of air and dielectric modes can be realized by introducing central aperiodic mirrors with multiple bandgaps. The realization of coexistence of air and dielectric modes in single nanocavity will offer opportunities for multifunctional devices, paving the way to integrated multi-parameter sensors, filters, nonlinear devices, and compact light sources.

Ovarian cancer starts in the ovaries in its earlier stages and then spreads to the pelvis, uterus, and abdominal region. The success of an ovarian cancer treatment depends on the stage of the cancer and the diagnostic system. Squamous cell carcinoma antigen (SCC-Ag) is one of the most efficient cancer biomarkers, and elevated levels of SCC-Ag in ovarian cancer cells have been used to identify ovarian cancer. Carbon is a potential material for biosensing applications due to its thermal, electrical, and physical properties. Multiwalled carbon nanotubes (MWCNTs) are carbon-based materials that can be used here to detect SCC-Ag. Anti-SCC-Ag antibody was immobilized on the amine-modified MWCNT dielectric sensing surface to detect SCC-Ag. The uniformity of the surface structure was measured with a 3D nanoprofiler, and the results confirmed the detection of SCC-Ag at ∼80 pM. The specific detection of SCC-Ag was confirmed with two control proteins (factor IX and human serum albumin), and the system did not show biofouling. This experimental set-up with MWCNTs a dielectric sensing surface can lead to the detection of ovarian cancer in its initial stages.

This paper investigates the robust direct yaw-moment control (DYC) through parameter-dependent fuzzy sliding mode control (SMC) approach for all-wheel-independent-drive electric vehicles (AWID-EVs) subject to network-induced delays. AWID-EVs have obvious advantages in terms of DYC over the traditional centralized-drive vehicles. However it is one of the most principal issues for AWID-EVs to ensure the robustness of DYC. Furthermore, the network-induced delays would also reduce control performance of DYC and even deteriorate the EV system. To ensure robustness of DYC and deal with network-induced delays, a parameter-dependent fuzzy sliding mode control (FSMC) method based on the real-time information of vehicle states and delays is proposed in this paper. The results of cosimulations with Simulink® and CarSim® demonstrate the effectiveness of the proposed controller. Moreover, the results of comparison with a conventional FSMC controller illustrate the strength of explicitly dealing with network-induced delays.

Dysfunction of the ubiquitin-proteasome system (UPS) and calcium homeostasis has been implicated in the neurodegeneration of Alzheimer's and Parkinson's diseases. The cytosolic calcium concentration is maintained by store-operated calcium entry (SOCE), which is repressed by Alzheimer's disease-associated mutants, such as mutant presenilins. We hypothesized that inhibition of UPS impacts SOCE. This study showed that pretreatment with sub-lethal levels of proteasome inhibitors, including MG-132 and clasto-lactacystin-β-lactone (LA), reduced SOCE after depletion of endoplasmic reticulum calcium in rat neurons. With the same treatment, MG-132 and LA reduced the protein levels of stromal interaction molecule 1and 2 (STIM1/2), but not the levels of Orai1 and canonical transient receptor potential channel 1 (TRPC1). STIM1 or STIM2 protein was mobilized to lysosome by MG-132/LA treatment as observed under an immunofluorescence confocal laser microscope. In the neurons, MG-132 and LA degraded p62/SQSTM1, promoted autophagy, converted LC3I to LC3II, and promoted co-localization of LC3 and lysosomes. Rapamycin, which enhances autophagy, reduced STIM1/2 protein levels, whereas bafilomycin, which inhibits autophagy, increased their protein levels. The protein levels of STIM1/2 and the amplitude of SOCE were decreased in SH-SY5Y with decreased protein level of proteasome subunit beta type-5 induced by shRNA. We conclude that sub-lethal levels of proteasome inhibition reduce SOCE and promote autophagy-mediated degradation of STIM1/2. UPS inhibition, a common finding in neurodegenerative diseases, interferes with calcium homeostasis via repression of SOCE.

We report an aluminum nitride on insulator platform for mid-infrared (MIR) photonics applications beyond 3 μm. Propagation loss and bending loss are studied, while functional devices such as directional couplers, multimode interferometers, and add/drop filters are demonstrated with high performance. The complementary metal-oxide-semiconductor-compatible aluminum nitride offers advantages ranging from a large transparency window, high thermal and chemical resistance, to piezoelectric tunability and three-dimensional integration capability. This platform can have synergy with other photonics platforms to enable novel applications for sensing and thermal imaging in MIR.

In this paper, we present a broadband directional coupler (DC) based dual mode chemical sensor for the mid-infrared (MIR). For the first time, we propose chemical sensing based on refractive index (RI) change in a compact DC by incorporating a subwavelength grating (SWG) structure into conventional DC that introduces a sharp Bragg wavelength. Meanwhile, the SWG structure can also engineer the dispersion in the DC to achieve broadband operation so that the device can operate in a wide wavelength range that benefits spectrum analysis in the MIR. Fivefold enhancement in the operation bandwidth compared to conventional DCs has been achieved for 100% coupling efficiency experimentally. The sensing capability of the device for dichloromethane (CH 2 Cl 2 ) detection in ethanol (C 2 H 5 OH) is investigated by simulation. A sensitivity of −0.47% self-normalized transmitted power change per percentage of CH 2 Cl 2 concentration is revealed in the RI sensing mode while 0.12% change in the total integrated output power is realized in the absorption sensing mode.

Surface-enhanced infrared absorption (SEIRA) technique has been focusing on the metallic resonator structures for decades while the dissipative loss and strong heating from metal are the intrinsic drawbacks. Meanwhile, gas sensor is also challenging for SEIRA because of the small size and weak absorption of gas. This paper reports an all dielectric photonic crystal slab (PCS) platform integrated with gas selective enrichment polymer polyethylenimine (PEI) as a miniaturized gas sensor, achieving a detection limit of 20 ppm and a fast response time of 2 min in CO 2 sensing.

Midinfrared (MIR), which covers numerous molecular vibrational fingerprints, has attracted enormous research interest due to its promising potential for label-free and damage-free sensing. Despite intense development efforts, the realization of waveguide-integrated on-chip sensing system has seen very limited success to date. The huge lattice mismatch between silicon and the commonly used detection materials such as HgCdTe, III-V, or II-VI compounds has been the key bottleneck that hinders their integration. Here, we realize an integration of silicon-on-insulator (SOI) waveguides with black phosphorus (BP) photodetectors. When operating near BP's cutoff wavelength where absorption is weak, the light-BP interaction is enhanced by exploiting the optical confinement in the Si waveguide and grating structure to overcome the limitation of absorption length constrained by the BP thickness. Devices with different BP crystal orientation and thickness are compared in terms of their responsivity and noise equivalent power (NEP). Spectral photoresponse from 3.68 to 4.03 μm was investigated. Additionally, power-dependent responsivity and gate-tunable photocurrent were also studied. At a bias of 1 V, the BP photodetector achieved a responsivity of 23 A/W at 3.68 μm and 2 A/W at 4 μm and a NEP less than 1 nW/Hz

We investigate nanocavities in deterministic aperiodic photonic crystal (PhC) nanobeams. We reveal that even a single nanocavity can support multiple mode-matched resonances, which show an almost perfect field overlap in the cavity region. The unique property is enabled by the existence of adjustable multiple bandgaps in deterministic aperiodic PhC nanobeams. Our investigation may inspire related studies on low threshold lasers, integrated nonlinear devices, optical filters, and on-chip sensors.

In this paper, we report a compact wavelength-flattened directional coupler (WFDC) based chemical sensor featuring an incorporated subwavelength grating (SWG) structure for the mid-infrared (MIR). By incorporating a SWG structure into directional coupler (DC), the dispersion in DC can be engineered to allow broadband operation which is advantageous to extract spectroscopic information for MIR sensing analysis. Meanwhile, the Bragg reflection introduced by the SWG structure produces a sharp trough at the Bragg wavelength. This sharp trough is sensitive to the surrounding refractive index (RI) change caused by the existence of analytes. Therefore, high sensitivity can be achieved in a small footprint. Around fivefold enhancement in the operation bandwidth compared to conventional DC is achieved for 100% coupling efficiency in a 40 &micro, m long WFDC experimentally. Detection of dichloromethane (CH2Cl2) in ethanol (C2H5OH) is investigated in a SWG-based WFDC sensor 136.8 &micro, m long. Sensing performance is studied by 3D finite-difference time domain (FDTD) simulation while sensitivity is derived by computation. Both RI sensing and absorption sensing are examined. RI sensing reveals a sensitivity of &minus, 0.47% self-normalized transmitted power change per percentage of CH2Cl2 concentration while 0.12% change in the normalized total integrated output power is realized in the absorption sensing. As the first demonstration of the DC based sensor in the MIR, our device has the potential for tertiary mixture sensing by utilizing both changes in the real and imaginary part of RI. It can also be used as a broadband building block for MIR application such as spectroscopic sensing system.

The design, fabrication and characterization of one-dimensional (1D) grating waveguide as slow light structure working in mid-infrared region are demonstrated for the first time. The effects of various structural parameters on slow light properties are systematically investigated through simulation and experiment, providing solid guidance on slow light engineering in 1D grating waveguide.

We demonstrate the first black phosphorus phototransistor integrated with Si photonics waveguide system towards mid-infrared (MIR) sensing. At a wavelength of 3.78 µm, the black phosphorus phototransistor achieves a high responsivity of 0.7 A/W under a small drain bias of −1 V at room-temperature. Additionally, the device offers gate and drain bias tunability to suppress dark current while simultaneously optimize photo-response performance. Our results reveal the potential of black phosphorus for MIR detection to enable the realization of integrated on-chip systems for MIR sensing applications.

We design, fabricate and characterize one-dimensional (1D) grating waveguide with flat band slow light effect in mid-infrared (MIR) region for the first time. The effects of various structural parameters on slow light properties are systematically investigated through theoretical analysis, simulation and experimental verification, providing solid guidance on slow light engineering in 1D grating waveguide. By adjusting structural parameters, average group indices of 9.4-15.5 with bandwidths of 23–66 nm and normalized delay-bandwidth products of 0.093-0.164 are obtained. The proposed structure provides a promising platform for various MIR applications such as on-chip optical buffers, modulators and absorption-based biochemical sensors.

Regulation of serine racemase (SR) occurs at transcriptional and translational levels; post-translational modification, cytosolic distribution as well as allosteric effect regulate SR activity. In this study, we report a new route of SR regulation, i.e. oxidative stress and hypermethylation of the srr (gene of SR) promoter correlate with its reduced transcription in aging rat cerebella. We first showed that the mRNA and protein level of srr were decreased in the homogenates of rat cerebellum at age 12 months compared with the counterparts from age 20 days. The reduction of SR protein level in aging cerebella was evidenced by decreased immunostaining observed in the cell body of granule cells or Purkinje cells. Staining for 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker for oxidative stress to DNA, was much stronger in granule cell or Purkinje cell nuclei from rat cerebella at 12 months compared with staining at 20 days. We further detected srr promoter hypermethylation at 12 months compared with that at 20 days by use of bisulfite sequencing PCR, coinciding with elevated protein levels of DNA methyltransferase 1 (DNMT1) in homogenates of aging cerebella. In vitro, we demonstrated that chronic treatment with the oxidant, menadione (VK3), reduced srr mRNA levels, which was reversed by the DNA demethylating agent 5-Aza-dC-2'-deoxycytidine (5-Aza-dC) in primary cerebellar granule cell cultures. Together, the in vivo and ex vivo results suggest that oxidative DNA stress and srr promoter hypermethylation are associated with reduced srr gene transcription and corresponding reduced protein expression in aging cerebella.

The cationic biopolymer ε-polylysine (ε-PL) is a food-grade antimicrobial that is highly effective against food pathogens and spoilage organisms. In compositionally complex environments, the antimicrobial activity of cationic ε-PL is likely to be impacted by its interactions with other charged species. The purpose of this study was to characterize the interactions of cationic ε-PL with various food grade biopolymers with different charge characteristics: anionic (carrageenan, alginate, pectin), neutral (dextran), and cationic (chitosan). Isothermal titration calorimetry (ITC), micro-electrophoresis (ME) and turbidity measurements were used to characterize the interactions and the nature of any aggregates formed. Our measurements suggested that there was little interaction or complex formation between cationic ε-PL and cationic or neutral biopolymers, but that strong electrostatic interactions and complex formation occurred between cationic ε-PL and anionic biopolymers. The solubility of the aggregates formed depended on biopolymer type and the mass ratio of biopolymers to ε-PL. The results of this study have important implications for the application of ε-PL in compositionally complex systems.

Outbreaks of foodborne illness from consumption of sprouts have been linked to contaminated seeds prior to germination. Due to the long sprouting period at ambient temperatures and high humidity, germinating seeds contaminated with low pathogen levels (0.1logCFU/g) can result in sprouts with high numbers (≥10(8)CFU/g) of pathogens. Currently, the recommended treatment method involves soaking seeds in 20,000ppm (2%) calcium hypochlorite prior to germination. In this study, an alternative treatment involving soaking seeds in a carvacrol nanoemulsion was tested for its efficacy against Salmonella enterica subspecies enterica serovar Enteritidis (ATCC BAA-1045) or EGFP expressing E. coli O157:H7 (ATCC 42895) contaminated mung bean and alfalfa seeds. The antimicrobial treatment was performed by soaking inoculated seed batches in the spontaneous nanoemulsion (4000 or 8000ppm) for 30 or 60min. The spontaneous nanoemulsion was formed by titrating the oil phase (carvacrol and medium chain triglycerides) and water-soluble surfactant (Tween 80®) into sodium citrate buffer. Following treatment, the numbers of surviving cells were determined by suspending the seeds in TSB and performing plate counts and/or Most Probable Number (MPN) enumeration. Treated seeds were sprouted and tested for the presence of the appropriate pathogen. This treatment successfully inactivated low levels (2 and 3logCFU/g) of S. Enteritidis and E. coli on either seed types when soaked for either 30 or 60min at nanoemulsion concentrations corresponding to 4000 (0.4%) or 8000 (0.8%) ppm carvacrol. Inoculated alfalfa seeds treated with 4000ppm nanoemulsion, required a 60min treatment time to show a similar 2-3 log reduction. Complete inactivation was confirmed by germinating treated seeds and performing microbiological testing. Total sprout yield was not compromised by any of the tested treatments. These results show that carvacrol nanoemulsions may be an alternative antimicrobial treatment method for mung bean and alfalfa seeds.

Nanoemulsions are particularly suitable as a platform in the development of delivery systems for lipophilic functional agents. This study shows that transparent orange oil nanoemulsions can be fabricated using an isothermal low-energy method (spontaneous emulsification), which offers the advantage of fabricating flavor oil delivery systems using rapid and simple processing operations. Orange oil nanoemulsions were formed spontaneously by titration of a mixture of orange oil, carrier oil [medium-chain triglyceride (MCT)], and non-ionic surfactant (Tween) into an aqueous solution (5 mM citrate buffer at pH 3.5) with continuous stirring. The oil/emulsion ratio content was kept constant (10 wt %), while the surfactant/emulsion ratio (SER) was varied (2.5-20 wt %). Oil-phase composition (orange oil/MCT ratio), SER, and surfactant type all had an appreciable effect on nanoemulsion formation and stability. Transparent nanoemulsions could be formed under certain conditions: 20% surfactant (Tween 40, 60, or 80) and 10% oil phase (4-6% orange oil + 6-4% MCT). Surfactant type and oil-phase composition also affected the thermal stability of the nanoemulsions. Most of the nanoemulsions broke down after thermal cycling (from 20 to 90 °C and back to 20 °C); however, one system remained transparent after thermal cycling: 20% Tween 80, 5% orange oil, and 5% MCT. The mean droplet size of these nanoemulsions increased over time, but the droplet growth rate was reduced appreciably after dilution. These results have important implications for the design and utilization of nanoemulsions as delivery systems in the food and other industries.

ɛ-Polylysine (ɛ-PL) is a potent food-grade cationic antimicrobial but its application within foods and beverages is currently limited because of its tendency to associate with anionic substances, thereby increasing product turbidity or forming sediments. In this study, we examined a potential means of overcoming these problems by forming electrostatic complexes between cationic ɛ-PL and anionic gum arabic (GA). The nature of the complexes formed depended on the mass ratio of gum arabic-to-ɛ-PL (RGA–PL), since this determined their electrical charge, aggregation stability, and antimicrobial efficacy. The electrical charge on the complexes went from positive to negative with increasing RGA–PL, with the point of zero charge being around RGA–PL ∼15. Soluble complexes were formed at low and high RGA–PL levels, but insoluble complexes were formed at intermediate levels (i.e. 5

The distribution and survival of Listeria monocytogenes (L. monocytogenes) in food processing environment is linked to its ability to form biofilms, however the genetic mechanisms remain unclear. In our previous study, a Himar1 mariner-based transposon mutagenesis was performed and 42 mutants were confirmed to have reduced biofilm formation. Among the 42 biofilm deficient mutants, two isolates (s25-10C and s55-1D) harbored single insertion in lmo1386, a gene encoding a putative DNA translocase. The lmo1386 mutants had impaired biofilm formation in both static and flow conditions. The mutant strain s55-1D was complemented by cloning the entire lmo1386 gene into pPL2-gtcAP, a derivative of the integration vector pPL2 with the L. monocytogenes gtcA promoter. The genetically complemented mutant restored its biofilm phenotype, demonstrating the role of lmo1386 in the biofilm formation of L. monocytogenes. The lmo1386 mutant had reduced initial adhesion ability, which could at least partially contribute to the impaired biofilm phenotype. Additionally, the lmo1386 mutant formed elongated cell chains when grown in a nutrient TSBYE media, while no obvious cell morphology changes were observed when grown in the minimal MWB media. Overall, our findings suggest that the disruption of lmo1386, a putative DNA translocase gene affects the biofilm formation of L. monocytogenes on abiotic surfaces, which may further advance the understanding of the complicated process of biofilm formation.

We experimentally report the bidirectional reconfiguration of an out-of-plane deformable microcantilever based metamaterial for advanced and dynamic manipulation of terahertz waves. The microcantilever is made of a bimaterial stack with a large difference in the coefficient of thermal expansion of the constituent materials. This allows for the continuous deformation of microcantilevers in upward or downward direction in response to positive or negative temperature gradient, respectively. The fundamental resonance frequency of the fabricated microcantilever metamaterial is measured at 0.4 THz at room temperature of 293 K. With decreasing temperature, the resonance frequency continuously blue shifts by 30 GHz at 77 K. On the other hand, with increasing temperature, the resonance frequency gradually red shifts by 80 GHz and saturates at 0.32 THz for 400 K. Furthermore, as the temperature is increased above room temperature, which results in the downward actuation of the microcantilever, a significant resonance line-narrowing with an enhanced quality factor is observed due to tight field confinement in the metamaterial structure. The thermal control of the microcantilever possesses numerous inherent advantages such as enhanced tunable range (∼37.5% in this work compared to previously reported microcantilever metamaterials), continuous tunability, and repeatable operations. The microcantilever metamaterial also shows high robustness to operate at cryogenic conditions and hence opens up the possibility of using meta-devices in harsh environments such as space, polar, and deep sea applications. Published version