Calculation and measurement of trapping stiffness in femtosecond optical tweezers.

Due to the characteristics of ultra-short pulse width and ultra-high peak power, femtosecond pulse laser can effectively induce nonlinear optical effects in trapped objects. As a result, it holds great value in the fields of micro and nano manipulation, microfluidics, and cell biology. However, the nonlinear optical effects on the stiffness of femtosecond optical traps remain unclear. Calibration of trap stiffness is crucial for accurately measuring forces and manipulating small particles. In this paper, we compare the stiffness between femtosecond optical traps and continuous wave optical traps. Experimental results demonstrate that the stiffness of the femtosecond optical trap in the splitting direction is greater than that in other directions and the stiffness of the continuous wave optical trap under the same laser power condition. Additionally, as the laser power increases, the stiffnesses of both the femtosecond optical trap and the continuous wave optical trap gradually increases. In contrast to a linear increase of the continuous wave optical trap, the stiffness of the femtosecond optical trap exhibits an exponential rise with increasing laser power. This research provides guidance and reference for improving the force measurement accuracy of femtosecond optical tweezer system.

Programmable photoacoustic manipulation of microparticles in liquid.

Particle manipulation through the transfer of light or sound momentum has emerged as a powerful technique with immense potential in various fields, including cell biology, microparticle assembly, and lab-on-chip technology. Here, we present a novel method called Programmable Photoacoustic Manipulation (PPAM) of microparticles in liquid, which enables rapid and precise arrangement and controllable transport of numerous silica particles in water. Our approach leverages the modulation of pulsed laser using digital micromirror devices (DMD) to generate localized Lamb waves in a stainless steel membrane and acoustic waves in water. The particles undergo a mechanical force of about several µN due to membrane vibrations and an acoustic radiation force of about tens of nN from the surrounding water. Consequently, this approach surpasses the efficiency of optical tweezers by effectively countering the viscous drag imposed by water and can be used to move thousands of particles on the membrane. The high power of the pulsed laser and the programmability of the DMD enhance the flexibility in particle manipulation. By integrating the benefits of optical and acoustic manipulation, this technique holds great promise for advancing large-scale manipulation, cell assembly, and drug delivery.

Programmable spin and transport of a living shrimp egg through photoacoustic pressure.

In the fields of biomedicine and microfluidics, the non-contact capture, manipulation, and spin of micro-particles hold great importance. In this study, we propose a programmable non-contact manipulation technique that utilizes photoacoustic effect to spin and transport living shrimp eggs. By directing a modulated pulsed laser toward a liquid-covered stainless-steel membrane, we can excite patterned Lamb waves within the membrane. These Lamb waves occur at the interface between the membrane and the liquid, enabling the manipulation of nearby particles. Experimental results demonstrate the successful capture, spin, and transport of shrimp eggs in diameter of 220 µm over a distance of about 5 mm. Calculations indicate that the acoustic radiation force and torque generated by our photoacoustic manipulation system are more than 299.5 nN and 41.0 nN·mm, respectively. The system surpasses traditional optical tweezers in terms of force and traditional acoustic tweezers in terms of flexibility. Consequently, this non-contact manipulation system significantly expands the possibilities for applications in various fields, including embryo screening, cell manipulation, and microfluidics.

Ultra-sensitive amplitude engineering and sign reversal of circular dichroism in quasi-3D chiral nanostructures.

Circular dichroism (CD), as one of the most representative chiroptical effects, provides a simple strategy for the detection and characterization of the molecular chirality. The enhancement and sign reversal of CD are of great importance for its practical applications in chiral bio-sensing, chirality switching and optical filtering, etc. Here, we realize considerable adjustments and the sign reversal of CD in quasi-three-dimensional (quasi-3D) combined Archimedean spiral nanostructures. With special local and lattice configurations, the nanostructures have both right-handed and left-handed geometric chirality, which are designed based on the proximity effect of stencil lithography. We find that the CD response of the nanostructures becomes obvious once its height exceeds 200 nm and can be adjusted by the further increase of the height or the change of the blade spacing of the nanostructures. The CD reversal is achieved by utilizing the competition of two chiral centers when the height or blade spacing exceeds a critical value. Further analysis of the scattering power of multipole moments reveals that the CD modulation is determined by both magnetic dipole moment and electric quadrupole moment. Benefiting from the highly sensitive CD response to the height, the extreme sign reversal of CD is achieved when a sub-10-nm ultrathin medium layer is anchored on the surface of the nanostructures, which provides a promising strategy for ultra-sensitive chiral bio-sensing.

High-quality multiple-working-wavelength photonic crystal diodes based on the Fano resonance of nonlinear defects.

All-optical photonic crystal diodes based on the Fano resonance of nonlinear defects are studied. The diodes can achieve nonreciprocal transmission ratios of 31.7 dB and 33.9 dB at working wavelengths of 1534.83 nm and 1536.02 nm, respectively. The function of two defects' coupling to the performance of unidirectional light transmission is also analyzed. When two Fano cavities are cascaded to form a two-branch-channel diode, unidirectional light propagation at 1536.88, 1538.76, 1612.80, and 1616.78 nm wavelengths is achieved along two opposite forward directions, and the nonreciprocal transmission ratios are 36.5, 30.3, 23.9, and 19.6 dB, respectively.

Generating arbitrary photoacoustic fields with a spatial light modulator.

Ultrasound fields have broad applications in imaging, sensing, medical therapy, etc. In these applications, it is of great importance to generate desired ultrasound fields. The generation of arbitrary ultrasound fields is challenging using phased array transducers or a monolithic acoustic hologram. In this work, by taking advantage of the photoacoustic effect and spatial light modulating technique, we demonstrate that dynamic and high-resolution arbitrary acoustic fields in liquid can be realized. We clearly show ultrasonic vortex and arbitrary 2D/3D ultrasonic fields in our photoacoustic system. All the measured pressure fields agree well with the desired ones. We anticipate these rapidly tunable photoacoustic fields will find applications in dynamic acoustic tweezers and ultrasonic imaging.

Three-output-channel photonic crystal splitter and switch based on nonlinear resonators and the self-collimation characteristics of a light beam.

Based on the nonlinear resonators and self-collimation characteristics of light beams, we designed an all-optical photonic crystal beam splitter and switch. The proposed device consists of an input waveguide and three output waveguides connected to different ring resonators. Three pump beams transmit through different resonators via the self-collimation effect, and eight output states are realized by altering the intensity of the pump light. The proposed device works at the wavelength of 1629.57 nm, and the pump wavelength is located at 1240.00 nm. The transmittance contrast between the "on" and "off" states reached a maximum value of 124.0 and a minimum of 17.6. The minimal pump light intensity required to implement the performance is only ${0.162}\,\,{\rm W/}\unicode{x00B5}{\rm m}^2$0.162W/µm2, while the maximal value is about ${0.497}\,\,{\rm W/}\unicode{x00B5}{\rm m}^2$0.497W/µm2. Due to the small size of our proposed device and also its insensitivity to the pump light beams' incident location and spatial width within a certain degree, it has great potential application value in all-optical communications.

High-sensitivity quasi-periodic photonic crystal biosensor based on multiple defective modes.

The sensitivities of the octagonal quasi-periodic photonic crystal (QPC) defective modes are theoretically studied. The octagonal QPC biosensors are composed of silicon columns arranged in a liquid background. By designing a defect structure, a variety of localized modes with different spatial symmetries and field profiles are obtained, and a maximum refractive index sensitivity 800 nm/RIU is achieved around 1500 nm transmission peak when the central rod's size equals 100 nm, and the corresponding detection limit reaches 0.00042. The liquid can flow freely among the rods through the entire structure, so it is convenient to monitor the concentration of protein in the liquid environment dynamically. The influence of the protein's thickness to the shift of the resonant wavelength is also studied, where a minimum protein's thickness of less than 10 nm can be detected by optimizing the central column's size to be 400 nm, and the spatial field profiles of different resonant modes are analyzed to explain the corresponding sensitivities.

Comparative study on fermentation performance in the genome shuffled Candida versatilis and wild-type salt tolerant yeast strain.

BACKGROUND: The fermentation performance of a genome-shuffled strain of Candida versatilis S3-5, isolated for improved tolerance to salt, and wild-type (WT) strain were analysed. The fermentation parameters, such as growth, reducing sugar, ethanol, organic acids and volatile compounds, were detected during soy sauce fermentation process. RESULTS: The results showed that ethanol produced by the genome shuffled strain S3-5 was increasing at a faster rate and to a greater extent than WT. At the end of the fermentation, malic acid, citric acid and succinic acid formed in tricarboxylic acid cycle after S3-5 treatment elevated by 39.20%, 6.85% and 17.09% compared to WT, respectively. Moreover, flavour compounds such as phenethyl acetate, ethyl vanillate, ethyl acetate, isoamyl acetate, ethyl myristate, ethyl pentadecanoate, ethyl palmitate and phenylacetaldehyde produced by S3-5 were 2.26, 2.12, 2.87, 34.41, 6.32, 13.64, 2.23 and 78.85 times as compared to WT. CONCLUSIONS: S3-5 exhibited enhanced metabolic ability as compared to the wild-type strain, improved conversion of sugars to ethanol, metabolism of organic acid and formation of volatile compounds, especially esters, Moreover, S3-5 might be an ester-flavour type salt-tolerant yeast. © 2016 Society of Chemical Industry.

Single-molecule observation of helix staggering, sliding, and coiled coil misfolding.

The biological functions of coiled coils generally depend on efficient folding and perfect pairing of their α-helices. Dynamic changes in the helical registry that lead to staggered helices have only been proposed for a few special systems and not found in generic coiled coils. Here, we report our observations of multiple staggered helical structures of two canonical coiled coils. The partially folded structures are formed predominantly by coiled coil misfolding and occasionally by helix sliding. Using high-resolution optical tweezers, we characterized their energies and transition kinetics at a single-molecule level. The staggered states occur less than 2% of the time and about 0.1% of the time at zero force. We conclude that dynamic changes in helical registry may be a general property of coiled coils. Our findings should have broad and unique implications in functions and dysfunctions of proteins containing coiled coils.

Major Role of NAD-Dependent Lactate Dehydrogenases in the Production of l-Lactic Acid with High Optical Purity by the Thermophile Bacillus coagulans.

Bacillus coagulans 2-6 is an excellent producer of optically pure l-lactic acid. However, little is known about the mechanism of synthesis of the highly optically pure l-lactic acid produced by this strain. Three enzymes responsible for lactic acid production-NAD-dependent l-lactate dehydrogenase (l-nLDH; encoded by ldhL), NAD-dependent d-lactate dehydrogenase (d-nLDH; encoded by ldhD), and glycolate oxidase (GOX)-were systematically investigated in order to study the relationship between these enzymes and the optical purity of lactic acid. Lactobacillus delbrueckii subsp. bulgaricus DSM 20081 (a d-lactic acid producer) and Lactobacillus plantarum subsp. plantarum DSM 20174 (a dl-lactic acid producer) were also examined in this study as comparative strains, in addition to B. coagulans. The specific activities of key enzymes for lactic acid production in the three strains were characterized in vivo and in vitro, and the levels of transcription of the ldhL, ldhD, and GOX genes during fermentation were also analyzed. The catalytic activities of l-nLDH and d-nLDH were different in l-, d-, and dl-lactic acid producers. Only l-nLDH activity was detected in B. coagulans 2-6 under native conditions, and the level of transcription of ldhL in B. coagulans 2-6 was much higher than that of ldhD or the GOX gene at all growth phases. However, for the two Lactobacillus strains used in this study, ldhD transcription levels were higher than those of ldhL. The high catalytic efficiency of l-nLDH toward pyruvate and the high transcription ratios of ldhL to ldhD and ldhL to the GOX gene provide the key explanations for the high optical purity of l-lactic acid produced by B. coagulans 2-6.

Effect of salt-tolerant yeast of Candida versatilis and Zygosaccharomyces rouxii on the production of biogenic amines during soy sauce fermentation.

BACKGROUND: This study aimed to enhance and improve the quality and safety of soy sauce. In the present work, the change of biogenic amines, such as histamine, tyramine, cadaverine, spermidine, was examined by the treatment of Candida versatilis and Zygosaccharomyces rouxii, and the influence of salt-tolerant yeast on biogenic amines was analysed during the whole fermentation process. RESULTS: The results showed that the content of biogenic amines was elevated after yeast treatment and the content of biogenic amines was influenced by using yeast. The dominating biogenic amine in soy sauce was tyramine. At the end of fermentation, the concentrations of biogenic amines produced by Zygosaccharomyces rouxii and Candida versatilis in the soy mash were 122.71 mg kg(-1) and 69.96 mg kg(-1) . CONCLUSIONS: The changes of biogenic amines in high-salt liquid soy mash during fermentation process indicated that a variety of biogenic amines were increased in the fermentation ageing period, which may be due to amino acid decarboxylation to form biogenic amines by yeast decarboxylase. The fermentation period of soy sauce should be longer than 5 months because biogenic amines began to decline after this time period.

Programmable photoacoustic patterning of microparticles in air.

Optical and acoustic tweezers, despite operating on different physical principles, offer non-contact manipulation of microscopic and mesoscopic objects, making them essential in fields like cell biology, medicine, and nanotechnology. The advantages and limitations of optical and acoustic manipulation complement each other, particularly in terms of trapping size, force intensity, and flexibility. We use photoacoustic effects to generate localized Lamb wave fields capable of mapping arbitrary laser pattern shapes. By using localized Lamb waves to vibrate the surface of the multilayer membrane, we can pattern tens of thousands of microscopic particles into the desired pattern simultaneously. Moreover, by quickly and successively adjusting the laser shape, microparticles flow dynamically along the corresponding elastic wave fields, creating a frame-by-frame animation. Our approach merges the programmable adaptability of optical tweezers with the potent manipulation capabilities of acoustic waves, paving the way for wave-based manipulation techniques, such as microparticle assembly, biological synthesis, and microsystems.

Synergetic enhancement of CsPbI3 nanorod-based high-performance photodetectors via PbSe quantum dot interface engineering.

The advancement of optoelectronic applications relies heavily on the development of high-performance photodetectors that are self-driven and capable of detecting a wide range of wavelengths. CsPbI3 nanorods (NRs), known for their outstanding optical and electrical properties, offer direct bandgap characteristics, high absorption coefficients, and long carrier diffusion lengths. However, challenges such as stability and limited photoluminescence quantum yield have impeded their widespread application. By integrating PbSe colloidal quantum dots (CQDs) with CsPbI3 NRs, the hybrid nanomaterial harnesses the benefits of each component, resulting in enhanced optoelectronic properties and device performance. In this work, a self-powered and broadband photodetector, ITO/ZnO/CsPbI3:PbSe/CuSCN/Au, is fabricated, in which CsPbI3 NRs are decorated with PbSe QDs as the photoactive layer, ZnO as the electron-transporting layer and CuSCN as the hole-transporting layer. The device performance is further improved through the incorporation of Cs2CO3 into the ZnO layer, resulting in an enhancement of its overall operational characteristics. As a result, a notable responsivity of 9.29 A W-1 and a specific detectivity of 3.17 × 1014 Jones were achieved. Certainly, the TCAD simulations closely correlate with our experimental data, facilitating a comprehensive exploration of the fundamental physical mechanisms responsible for the improved performance of these surface-passivated heterojunction photodetectors. This opens up exciting possibilities for substantial advancements in the realm of next-generation optoelectronic devices.

The properties of gold nanospheres studied with dark field optical trapping.

We demonstrate trapping and characterization of multiple gold nanospheres with a setup composed of dark field imaging and optical tweezers. The number of trapped nanospheres is quantified by the overall dark-field scattering intensity. The spectra of the scattering intensity show that there is no interparticle coupling among trapped nanospheres when the density of nanospheres in the trap is low enough (less than 10 particles), while the density of nanosphere increases the interparticle coupling of nanospheres becomes obvious. In addition, the trapping potential of a single gold nanosphere is obtained by trapping an ensemble of gold nanospheres.

Application of proteomics to determine the mechanism of ozone on sweet cherries (Prunus avium L.) by time-series analysis.

This research investigated the mechanism of ozone treatment on sweet cherry (Prunus avium L.) by Lable-free quantification proteomics and physiological traits. The results showed that 4557 master proteins were identified in all the samples, and 3149 proteins were common to all groups. Mfuzz analyses revealed 3149 candidate proteins. KEGG annotation and enrichment analysis showed proteins related to carbohydrate and energy metabolism, protein, amino acids, and nucleotide sugar biosynthesis and degradation, and fruit parameters were characterized and quantified. The conclusions were supported by the fact that the qRT-PCR results agreed with the proteomics results. For the first time, this study reveals the mechanism of cherry in response to ozone treatment at a proteome level.

Smart hydrothermally responsive microneedle for topical tumor treatment.

Locoregional therapy has attracted increasing attention for subcutaneous tumors owing to its merits of minimally invasive operation and negligible systematic toxicity. However, to accelerate clinical translation, further promotions in deep-seated penetration, temporal-spatial controllability, personalized adaptability, as well as easy operation are still urgently needed. This work proposed a self-heating-cooking-package-inspired hydrothermally responsive multi-round acturable microneedle (HRMAM) system, which loaded docetaxel (DTX) in the polycaprolactone (PCL), to serve as deeply penetrable, hydrothermal-chemotherapy synergetic, on-demand and self-service anti-tumor treatment. The optimized hydrothermally responsive formulation served as base components for water-based self-heating responsive drug release with synergistic anti-tumor thermal therapy, and simultaneously in combination with well-designed grooved-structure needle tips for directional deep delivery and enhanced transfer efficiency. To satisfy spatial precision and flexible controllability, this engineering-based detachable HRMAM system was divided into three relatively independent segments, which were fitted perfectly with an original-designed applicator for ensuring easy operation in a smart self-service manner. Impressively, the HRMAM system achieved encouraging tumor growth inhibition of 75.11% and 72.29% in animal model of melanomas and breast carcinoma, respectively, much higher than those of other groups receiving traditional treatment, without obvious side effects. It was anticipated that the HRMAM system would manifest great promise to combat unreachable and deep-seated subcutaneous tumors, bellowing clinical values upon locoregional therapy products with high efficiency, low toxicity, flexible controllability, temporal-spatial precision, easy operation, as well as patient's painless, comfort and compliance.

Optical trapping of gold nanoparticles by cylindrical vector beam.

Optical trapping of gold nanoparticles is experimentally demonstrated using radially and azimuthally polarized beams. The transverse optical trapping stiffness of gold nanoparticles is measured. The radially polarized beam exhibits a higher trapping efficiency than the azimuthally polarized beam and the Gaussian beam. The transverse stiffness of particles with different diameters is measured experimentally and calculated via the discrete-dipole approximation method, and good agreement between theory and experiment is found.

Manipulation of gold nanorods with dual-optical tweezers for surface plasmon resonance control.

Gold nanorods are too tiny to be manipulated using conventional mechanical methods. In this paper, we demonstrate the trapping, transferring, positioning and patterning of gold nanorods with dual-optical tweezers. The convenient manipulations are achieved by taking advantage of the longitudinal surface plasmon resonance of gold nanorods and the anisotropic optical trapping forces formed by two linearly polarized Gaussian beams. The trapped gold nanoparticles are positioned extremely firmly and quickly on a substrate compared with randomly dispersed ones. It is observed that gold nanorods show advantages over gold nanospheres with regard to positioning speed and stability. More importantly, versatile plasmon coupling effects have been achieved in some patterned nanorods.

Light-induced tumor theranostics based on chemical-exfoliated borophene.

Among 2D materials (Xenes) which are at the forefront of research activities, borophene, is an exciting new entry due to its uniquely varied optical, electronic, and chemical properties in many polymorphic forms with widely varying band gaps including the lightest 2D metallic phase. In this paper, we used a simple selective chemical etching to prepare borophene with a strong near IR light-induced photothermal effect. The photothermal efficiency is similar to plasmonic Au nanoparticles, with the added benefit of borophene being degradable due to electron deficiency of boron. We introduce this selective chemical etching process to obtain ultrathin and large borophene nanosheets (thickness of ~4 nm and lateral size up to ~600 nm) from the precursor of AlB2. We also report first-time observation of a selective Acid etching behavior showing HCl etching of Al to form a residual B lattice, while HF selectively etches B to yield an Al lattice. We demonstrate that through surface modification with polydopamine (PDA), a biocompatible smart delivery nanoplatform of B@PDA can respond to a tumor environment, exhibiting an enhanced cellular uptake efficiency. We demonstrate that borophene can be more suitable for safe photothermal theranostic of thick tumor using deep penetrating near IR light compared to gold nanoparticles which are not degradable, thus posing long-term toxicity concerns. With about 40 kinds of borides, we hope that our work will open door to more discoveries of this top-down selective etching approach for generating borophene structures with rich unexplored thermal, electronic, and optical properties for many other technological applications.