Optical interference phase control method with single photodetector for interference lithography.

This study designs an optical phase control method for interference lithography system accompanied with severe disturbance. The system, which is designed based on the exponential reaching law of sliding mode control(SMCE), could adjust the interference phase with single photodetector. The model of system is derived and then the stability is proved through Lyapunov theorem. This paper also analyzes the behavior of the system under different reference voltages of photodetector. Both theoretical analysis and simulation experiment results suggest that this method can non-periodically achieve interference phase control with single photodetector by the switching module. Finally, the experimental device is set up, and the superiority of the SMCE method in transient response time and disturbance-resisting ability is demonstrated compared with the proportional-integral-derivative(PID) method.

Screening and Identification of a Novel Anti-Siglec-15 Human Antibody 3F1 and Relevant Antitumor Activity.

Sialic acid-binding Ig-like lectin-15 is an important immunosuppressive molecule considered to be a key target in next-generation tumor immunotherapy. In this study, we screened 22 high-affinity antibodies that specifically recognize human Siglec-15 by using a large human phage antibody library, and five representative sequences were selected for further study. The results showed the binding activity of five antibodies to Siglec-15 (EC50 ranged from 0.02368 µg/mL to 0.07949 µg/mL), and in two Siglec-15-overexpressed cell lines, three antibodies had the strongest binding activity, so the two clones were discarded for further study. Subsequently, the affinity of three antibodies were measured by bio-layer interferometry technology (5-9 × 10E-09M). As the reported ligands of Siglec-15, the binding activity of Siglec-15 and sialyl-Tn, cluster of differentiation 44, myelin-associated glycoprotein, and leucine-rich repeat-containing protein 4C can be blocked by three of the antibodies. Among these, 3F1 had a competitive advantage. Then, the antibody 3F1 showed an obvious antibody-dependent cell-mediated cytotoxicity effect (EC50 was 0.85 µg/mL). Further, antibody 3F1 can reverse the inhibitory effect of Siglec-15 on lymphocyte proliferation (especially CD4+T and CD8+T) and cytokine release Interferon-γ. Given the above results, 3F1 was selected as a candidate for the in vivo pharmacodynamics study. In the tumor model of Balb/c Nude mice, 3F1 (10 mg/kg) showed certain antitumor effects [tumor growth inhibition (TGI) was 31.5%], while the combination of 3F1 (5 mg/kg) and Erbitux (5 mg/kg) showed significant antitumor effects (TGI was 48.7%) compared with the PBS group. In conclusion, novel human antibody 3F1 has antitumor activity and is expected to be an innovative candidate drug targeting Siglec-15 for tumor immunotherapy. SIGNIFICANCE STATEMENT: Siglec-15 is considered as an important target in the next generation of tumor immunotherapy. 3F1 is expected to be the most promising potential candidate for targeting Siglec-15 for cancer treatment and could provide a reference for the development of antitumor drugs.

Localized tilted fiber Bragg gratings induced by femtosecond laser line-by-line inscription.

Localized tilted fiber Bragg gratings (TFBGs) with low insertion loss are reported. A series of second-order TFBGs with tilt angles of 0°, 7°, 14°, and 21° was inscribed line by line directly in a single-mode fiber. For the 7° TFBG, the Bragg resonance was 2.4 dB at 1550 nm, and the maximum cladding-mode resonance reached 24.6 dB with an insertion loss of 0.8 dB, the same level as that for TFBGs fabricated by the phase-mask method. The range in cladding-mode resonance for the TFBGs obtained was wider than 170 nm with an intensity exceeding 20 dB. Combined with microscope images, the formation of these localized TFBGs and their spectral performance are discussed. The effect of an inscription offset along the $y$-axis direction was further investigated. With increasing offset, the intensity of the cladding-mode resonance dropped rapidly. The refractive index response sensitivity of the 7° TFBG was measured at 507.54 nm/RIU.

Effect of Polystyrene Microplastics of Different Sizes to Escherichia coli and Bacillus cereus.

The toxicity of polystyrene (PS) particles of different sizes was investigated using Gram-negative Escherichia coli and Gram-positive Bacillus cereus. PS particles could inhibit the cell growth of E. coli but promote the cell growth of B. cereus, and this difference might be attributed to different composition in their cell walls and the different interactions between the two bacteria and PS particles. Direct adhesion of E. coli cells on the surface of 5 µm PS microbeads by flagella was observed, indicating the putative role of E. coli on biofilm formation of plastisphere. The regulations of malondialdehyde, lactate dehydrogenase and glutathione were similar between the two bacteria, so the difference in the toxicity effect of PS between the two bacteria was not caused by the antioxidant activity. The overall results of the present study could help to understand the responses of different bacteria to microplastic exposure.

Optimal Frequency and Amplitude of Vertical Viewpoint Oscillation for Improving Vection Strength and Reducing Neural Constrains on Gait.

Inducing self-motion illusions referred as vection are critical for improving the sensation of walking in virtual environments (VE). Adding viewpoint oscillations to a constant forward velocity in VE is effective for improving vection strength under static conditions. However, the effects of oscillation frequency and amplitude on vection strength under treadmill walking conditions are still unclear. Besides, due to the visuomotor entrainment mechanism, these visual oscillations would affect gait patterns and be detrimental for achieving natural walking if not properly designed. This study was aimed at determining the optimal frequency and amplitude of vertical viewpoint oscillations for improving vection strength and reducing gait constraints. Seven subjects walked on a treadmill while watching a visual scene. The visual scene presented a constant forward velocity equal to the treadmill velocity with different vertical viewpoint oscillations added. Five oscillation patterns with different combinations of frequency and amplitude were tested. Subjects gave verbal ratings of vection strength. The mediolateral (M-L) center of pressure (CoP) complexity was calculated to indicate gait constraints. After the experiment, subjects were asked to give the best and the worst oscillation pattern based on their walking experience. The oscillation frequency and amplitude had strong positive correlations with vection strength. The M-L CoP complexity was reduced under oscillations with low frequency. The medium oscillation amplitude had greater M-L CoP complexity than the small and large amplitude. Besides, subjects preferred those oscillation patterns with large gait complexity. We suggested that the oscillation amplitude with largest M-L CoP complexity should first be chosen to reduce gait constraints. Then, increasing the oscillation frequency to improve vection strength until individual preference or the boundary of motion sickness. These findings provide important guidelines to promote the sensation of natural walking in VE.

High purity optical vortex generation in a fiber Bragg grating inscribed by a femtosecond laser.

In this Letter, a method for orbital angular momentum (OAM) mode generation is proposed and experimentally demonstrated using a fiber Bragg grating (FBG) and off-axis incidence. The FBG fabricated by a femtosecond laser was used to couple the incidence beam into backward high-order modes. The generated modes were then reformed into ring-shaped OAM modes by adjusting the off-axis displacement of the input beam. The intensity distribution, phase vortex, and mode purity of the output light were experimentally investigated. Results indicates that the order of the generated OAM modes is dependent on the resonant wavelength of the FBG, and the sign of the OAM topological charge is determined by the displacement value of the off-axis incident light. In the experiment, ±1- and ±2-order OAM modes were achieved and confirmed, with purities as high as 90%, 91%, 89%, and 88%, respectively.

Local Dynamic Stability of Self-Paced Treadmill Walking Versus Fixed-Speed Treadmill Walking.

The purpose of this study was to assess the influence of gait stability induced by treadmill accelerations during self-paced treadmill walking (SPW). Local dynamic stability of three-dimensional (3D) upper body accelerations and hip angles were quantified. The results demonstrated that SPW was more unstable and had higher risk of falling than fixed-speed treadmill walking (FSW) under the impact of treadmill accelerations. The frequency domain analysis of treadmill speed indicated that intrastride treadmill speed variation was the dominating cause of the instability, and self-paced control strategies which can reduce the intrastride variation may achieve higher gait stability during SPW.

An Anisotropic Hydrogel Based on Mussel-Inspired Conductive Ferrofluid Composed of Electromagnetic Nanohybrids.

Anisotropic hydrogels with a hierarchical structure can mimic biological tissues, such as neurons or muscles that show directional functions, which are important factors for signal transduction and cell guidance. Here, we report a mussel-inspired approach to fabricate an anisotropic hydrogel based on a conductive ferrofluid. First, polydopamine (PDA) was used to mediate the formation of PDA-chelated carbon nanotube-Fe3O4 (PFeCNT) nanohybrids and also used as a dispersion medium to stabilize the nanohybrids to form a conductive ferrofluid. The ferrofluid can respond to an orientated magnetic field and be programed to form aligned structures, which were then frozen in a hydrogel network formed via in situ free-radical polymerization and gelation. The resulted hydrogel shows directional conductive and mechanical properties, mimicking an oriented biological tissue. Under external electrical stimulation, the orientated PFeCNT nanohybrids can be sensed by the myoblasts cultured on the hydrogel, resulting in the oriented growth of cells. In summary, the mussel-inspired anisotropic hydrogel with its aligned structural complexity and anisotropic properties together with the cell affinity and tissue adhesiveness is a potent multifunctional biomaterial for mimicking oriented tissues to guide cell proliferation and tissue regeneration.

Two-dimensional vector bending sensor based on seven-core fiber Bragg gratings.

We demonstrated a two-dimensional vector-bending sensor by use of fiber Bragg gratings (FBGs) inscribed in a homogeneous seven-core fiber. Seven FBGs were simultaneously inscribed in each of all seven cores using a modified Talbot interferometer and a lens scanning method. The vector bending response of six outer-core FBGs was investigated at all 360° directions with a step size of 15°. The bending sensitivities of the six outer-core FBGs display six perfect '8'-shaped patterns in a polar-coordinate system. That is, they exhibit strong bending-direction dependence with a maximum sensitivity of 59.47 pm/m-1. The orientation and amplitude of the vector bending can be reconstructed using measured Bragg wavelength shifts of any two off-diagonal outer-core FBGs. So, the six outer-core FBGs have 12 combinations for bend reconstruction, which can be averaged across multiple reconstructions to develop an accurate two-dimensional vector bending sensor. The average relative error was lower than 4.5% for reconstructed amplitude and less than 2.8% for reconstructed orientation angle θ. Moreover, the seven-core FBGs offer several advantages such as a compact structure, fabrication flexibility, and the temperature compensating ability of central-core FBG.

Femtosecond laser-inscribed fiber interface Mach-Zehnder interferometer for temperature-insensitive refractive index measurement.

A new fiber interface Mach-Zehnder interferometer has been fabricated, to the best of our knowledge, in coreless fiber by femtosecond laser-inscription for temperature-insensitive refractive index measurement. A straight waveguide was inscribed along the central axis of the coreless fiber as the reference arm, and the other curved waveguide (interface waveguide) was then inscribed bending toward the cladding interface to obtain a strong evanescent field sensitive to ambient refractive index. This fiber interface Mach-Zehnder interferometer exhibits a high refractive index (RI) sensitivity of ∼3000 nm/RIU at an RI value of 1.432. Moreover, with the significant advantages of high mechanical strength and temperature independence, such a fiber Mach-Zehnder interferometer may find many potential applications in biochemical sensing.

Sapphire fiber Bragg gratings inscribed with a femtosecond laser line-by-line scanning technique.

We propose and demonstrate the fabrication of single-crystal sapphire fiber Bragg gratings (SFBGs) using a femtosecond laser line-by-line scanning technique. This approach provides a robust method for producing SFBGs at various Bragg wavelengths with an acceptable reflectivity. The spectrum characteristics of the SFBGs with various fiber diameters, track lengths, and grating pitch quantities were investigated. An SFBG with a reflectivity of 6.3% was obtained via optimization of fabrication parameters. Additionally, a serial array consisting of five SFBGs at different wavelengths was successfully constructed. The high-temperature response of these SFBGs was tested and the experimental results showed the SFBGs could withstand a high temperature of 1612°C. Moreover, a temperature sensitivity of 36.5 pm/°C was achieved in the high-temperature region. Such SFBGs could be developed for promising high-temperature sensors in aero engines.

Fiber surface Bragg grating waveguide for refractive index measurements.

A fiber surface Bragg grating waveguide (BGW) fabricated in the surface of single-mode fiber by direct femtosecond laser inscription is demonstrated and successfully applied for refractive index (RI) measurements. Prior to laser inscription of the fiber surface BGW, an X-coupler is first inscribed across the fiber core to couple light from the core to the fiber surface. The light transmitted in the fiber surface BGW efficiently interacts with the surrounding medium due to a strong evanescent field, and obtains an acceptable RI sensitivity approaching ∼16 nm/RIU. The novel design efficiently couples the light guided in the core with the surrounding medium using a non-destructive, single-step micromachining process, and is expected to have potential applications in fiber biochemical sensing.

Highly-sensitive gas pressure sensor using twin-core fiber based in-line Mach-Zehnder interferometer.

A Mach-Zehnder interferometer based on a twin-core fiber was proposed and experimentally demonstrated for gas pressure measurements. The in-line Mach-Zehnder interferometer was fabricated by splicing a short section of twin-core fiber between two single mode fibers. A micro-channel was created to form an interferometer arm by use of a femtosecond laser to drill through one core of the twin-core fiber. The other core of the fiber was remained as the reference arm. Such a Mach-Zehnder interferometer exhibited a high gas pressure sensitivity of -9.6 nm/MPa and a low temperature cross-sensitivity of 4.4 KPa/°C. Moreover, ultra-compact device size and all-fiber configuration make it very suitable for highly-sensitive gas pressure sensing in harsh environments.

Highly birefringent phase-shifted fiber Bragg gratings inscribed with femtosecond laser.

We demonstrate a highly birefringent phase-shifted fiber Bragg grating (PS-FBG) inscribed in H2-free fiber with a near-infrared femtosecond Gaussian laser beam and uniform phase mask. The PS-FBG was fabricated from an ordinary fiber Bragg grating (FBG) in a case in which overexposure was applied. The spectral evolution from FBG to FS-FBG was observed experimentally with a decrease in transmission loss at dip wavelength, blueshift of the dip wavelength, decrease in the cladding mode loss, and an increase in the insertion loss. A high birefringence was demonstrated experimentally with the existence of PS-FBG only in TM polarization. The formation of the PS-FBG may be due to a negative index change induced by the higher intensity in the center of the Gaussian laser beam.

Simultaneous measurement of strain and temperature by employing fiber Mach-Zehnder interferometer.

We demonstrated a novel fiber in-line Mach-Zehnder interferometer (MZI) with a large fringe visibility of up to 17 dB, which was fabricated by misaligned splicing a short section of thin core fiber between two sections of standard single-mode fiber. Such a MZI could be used to realize simultaneous measurement of tensile strain and temperature. Tensile strain was measured with an ultrahigh sensitivity of -0.023 dB/µÉ› via the intensity modulation of interference fringes, and temperature was measured with a high sensitivity of 51 pm/°C via the wavelength modulation of interference fringe. That is, the MZI-based sensor overcomes the cross-sensitivity problem between tensile strain and temperature by means of different demodulation methods. Moreover, this proposed sensor exhibits the advantages of low-cost, extremely simple structure, compact size (only about 10 mm), and good repeatability.

Ultrasensitive refractive index sensor based on a Mach-Zehnder interferometer created in twin-core fiber.

We proposed and experimentally demonstrated a twin-core fiber (TCF)-based Mach-Zehnder interferometer (MZI) to develop an ultrasensitive refractive index (RI) sensor. This fiber MZI was constructed by splicing a short section of TCF between two sections of single mode fibers. A microchannel was drilled through one core of the TCF by means of femtosecond laser micromachining to create one arm of the proposed interferometer, and the other core worked as the second arm. Such a fiber interferometer exhibits an ultrahigh RI sensitivity of -10981 nm/RIU and a low temperature cross-sensitivity of 3.96×10(-6) RIU/°C. Moreover, the ultra-compact device size and all-fiber configuration make it very suitable for highly sensitive RI sensing at precise location.

High-sensitivity strain sensor based on in-fiber improved Fabry-Perot interferometer.

We demonstrated a high-sensitivity strain sensor based on an in-fiber Fabry-Perot interferometer (FPI) with an air cavity, which was created by splicing together two sections of standard single-mode fibers. The sensitivity of this strain sensor was enhanced to 6.0 pm/µÎµ by improving the cavity length of the FPI by means of repeating arc discharges for reshaping the air cavity. Moreover, such a strain sensor has a very low temperature sensitivity of 1.1 pm/°C, which reduces the cross sensitivity between tensile strain and temperature.

Compact tunable multibandpass filters based on liquid-filled photonic crystal fibers.

We demonstrated a compact tunable multibandpass filter with a short size of about 9 mm and a high wavelength-tuning sensitivity of up to -2.194 nm/°C by means of filling a liquid with a high refractive index of 1.700 into the air holes of a photonic crystal fiber (PCF). Such a PCF-based filter maintains an almost constant bandwidth and a large extinction ratio of more than 40 dB within the whole wavelength tuning range of more than 100 nm. Moreover, the transmission spectrum of the PCF-based filter is insensitive to the stretch force and the curvature of the fiber.

High-sensitivity strain sensor based on inflated long period fiber grating.

We demonstrated a high-sensitivity strain sensor based on an inflated long period fiber grating (I-LPFG). The I-LPFG was inscribed, for the first time to the best of our knowledge, by use of the pressure-assisted CO(2) laser beam scanning technique to inflate periodically air holes of a photonic crystal fiber. Such periodic inflations enhanced the sensitivity of the LPFG-based strain sensor to -5.62 pm/µÎµ. After high temperature annealing, the I-LPFG achieved a good repeatability and stability of temperature response with a sensitivity of 11.92 pm/°C.

Hyperbranched Dynamic Crosslinking Networks Enable Degradable, Reconfigurable, and Multifunctional Epoxy Vitrimer.

Degradation and reprocessing of thermoset polymers have long been intractable challenges to meet a sustainable future. Star strategies via dynamic cross-linking hydrogen bonds and/or covalent bonds can afford reprocessable thermosets, but often at the cost of properties or even their functions. Herein, a simple strategy coined as hyperbranched dynamic crosslinking networks (HDCNs) toward in-practice engineering a petroleum-based epoxy thermoset into degradable, reconfigurable, and multifunctional vitrimer is provided. The special characteristics of HDCNs involve spatially topological crosslinks for solvent adaption and multi-dynamic linkages for reversible behaviors. The resulting vitrimer displays mild room-temperature degradation to dimethylacetamide and can realize the cycling of carbon fiber and epoxy powder from composite. Besides, they have supra toughness and high flexural modulus, high transparency as well as fire-retardancy surpassing their original thermoset. Notably, it is noted in a chance-following that ethanol molecule can induce the reconstruction of vitrimer network by ester-exchange, converting a stiff vitrimer into elastomeric feature, and such material records an ultrahigh modulus (5.45 GPa) at -150 °C for their ultralow-temperature condition uses. This is shaping up to be a potentially sustainable advanced material to address the post-consumer thermoset waste, and also provide a newly crosslinked mode for the designs of high-performance polymer.