Single-Cell Synchro-Subtractive-Additive Nanoscale Surgery with Femtosecond Lasers.

Herein, an in situ "synchro-subtractive-additive" technique of femtosecond laser single-cell surgery (FLSS) is presented to address the inadequacies of existing surgical methods for single-cell manipulation. This process is enabled by synchronized nanoscale three-dimensional (3D) subtractive and additive manufacturing with ultrahigh precision on various parts of the cells, in that the precise removal and modification of a single-cell structure are realized by nonthermal ablation, with synchronously ultrafast solidification of the specially designed hydrogel by two photopolymerizations. FLSS is a minimally invasive technique with a post-operative survival rate of 70% and stable proliferation. It opens avenues for bottom-up synthetic biology, offering new methods for artificially synthesizing organelle-like 3D structures and modifying the physiological activities of cells.

Femtosecond Laser Fabrication of Three-Dimensional Bubble-Propelled Microrotors for Multicomponent Mechanical Transmission.

Inspired by the reverse thrust generated by fuel injection, micromachines that are self-propelled by bubble ejection are developed, such as microrods, microtubes, and microspheres. However, controlling bubble ejection sites to build micromachines with programmable actuation and further enabling mechanical transmission remain challenging. Here, bubble-propelled mechanical microsystems are constructed by proposing a multimaterial femtosecond laser processing method, consisting of direct laser writing and selective laser metal reduction. The polymer frame of the microsystems is first printed, followed by the deposition of catalytic platinum into the desired local site of the microsystems by laser reduction. With this method, a variety of designable microrotors with selective bubble ejection sites are realized, which enable excellent mechanical transmission systems composed of single and multiple mechanical components, including a coupler, a crank slider, and a crank rocker system. We believe the presented bubble-propelled mechanical microsystems could be extended to applications in microrobotics, microfluidics, and microsensors.

Photonic Molecule Approach to Multiorbital Topology.

The concepts of topology provide a powerful tool to tailor the propagation and localization of the waves. While electrons have only two available spin states, engineered degeneracies of photonic modes provide novel opportunities resembling spin degrees of freedom in condensed matter. Here, we tailor such degeneracies for the array of femtosecond laser written waveguides in the optical range exploiting the idea of photonic molecules: clusters of strongly coupled waveguides. In our experiments, we observe unconventional topological modes protected by the Z3 invariant arising due to the interplay of interorbital coupling and geometric dimerization mechanism. We track multiple topological transitions in the system with the change in the lattice spacings and excitation wavelength. This strategy opens an avenue for designing novel types of photonic topological phases and states.

Airflow Triggered Water Film Self-Sculpturing on Femtosecond Laser-Induced Heterogeneously Wetted Micro/Nanostructured Surfaces.

Liquid manipulation is essential for daily life and modern industry, and it is widely used in various fields, including seawater desalination, microfluidic robots, and biomedical engineering. Nevertheless, the current research focuses on the manipulation of individual droplets. There are a few projects for water film management. Here, we proposed a facile method of wind-triggered water film self-sculpturing based on a heterogeneous wettability surface, which is achieved by the femtosecond laser direct writing technology and femtosecond laser deposition. Under the conditions of various airflow velocities and water film thicknesses, three distinct behaviors of the water film were analyzed. As a result, when the water film thickness is lower than 4.9 mm, the self-sculpture process will occur until the whole superhydrophobic surface dewetting. Four potential applications are demonstrated, including encryption, oil containers, reconfigurable patterning, and self-splitting devices. This work provides a new approach for manipulating a water film of fluid control engineering.

High-Throughput Two-Photon 3D Printing Enabled by Holographic Multi-Foci High-Speed Scanning.

The emerging two-photon polymerization (TPP) technique enables high-resolution printing of complex 3D structures, revolutionizing micro/nano additive manufacturing. Various fast scanning and parallel processing strategies have been proposed to promote its efficiency. However, obtaining large numbers of uniform focal spots for parallel high-speed scanning remains challenging, which hampers the realization of higher throughput. We report a TPP printing platform that combines galvanometric mirrors and liquid crystal on silicon spatial light modulator (LCoS-SLM). By setting the target light field at LCoS-SLM's diffraction center, sufficient energy is acquired to support simultaneous polymerization of over 400 foci. With fast scanning, the maximum printing speed achieves 1.49 × 108 voxels s-1, surpassing the existing scanning-based TPP methods while maintaining high printing resolution and flexibility. To demonstrate the processing capability, functional 3D microstructure arrays are rapidly fabricated and applied in micro-optics and micro-object manipulation. Our method may expand the prospects of TPP in large-scale micro/nanomanufacturing.

Electrical Transport and Dynamics of Confined DNA through Highly Conductive 2D Graphene Nanochannels.

Confining DNA in nanochannels is an important approach to studying its structure and transportation dynamics. Graphene nanochannels are particularly attractive for studying DNA confinement due to their atomic flatness, precise height control, and excellent mechanical strength. Here, using femtosecond laser etching and wetting transfer, we fabricate graphene nanochannels down to less than 4.3 nm in height, with the length-to-height ratios up to 103. These channels exhibit high stability, low noise, and self-cleaning ability during the long-term ionic current recording. We report a clear linear relationship between DNA length and the residence time in the channel and further utilize this relationship to differentiate DNA fragments based on their lengths, ranging widely from 200 bps to 48.5 kbps. The graphene nanochannel presented here provides a potential platform for label-free analyses and reveals fundamental insights into the conformational dynamics of DNA and proteins in confined space.

Portable Triboelectric Electrostatic Tweezer for External Manipulation of Droplets within a Closed Femtosecond Laser-Treated Superhydrophobic System.

Controllable droplet manipulation has diverse applications; however, limited methods exist for externally manipulating droplets in confined spaces. Herein, we propose a portable triboelectric electrostatic tweezer (TET) by integrating electrostatic forces with a superhydrophobic surface that can even manipulate droplets in an enclosed space. Electrostatic induction causes the droplet to be subjected to an electrostatic force in an electrostatic field so that the droplet can be moved freely with the TET on a superhydrophobic platform. Characterized by its high precision, flexibility, and robust binding strength, TET can manipulate droplets under various conditions and achieve a wide range of representative fluid applications such as droplet microreactors, precise self-cleaning, cargo transportation, the targeted delivery of chemicals, liquid sorting, soft droplet robotics, and cell labeling. Specifically, TET demonstrated the ability to manipulate internal droplets from the outside of a closed system, such as performing cell labeling experiments within a sealed Petri dish without opening the culture system.

Large Field-of-View Nonlinear Holography in Lithium Niobate.

A nonlinear holographic technique is capable of processing optical information in the newly generated optical frequencies, enabling fascinating functions in laser display, security storage, and image recognition. One popular nonlinear hologram is based on a periodically poled lithium niobate (LN) crystal. However, due to the limitations of traditional fabrication techniques, the pixel size of the LN hologram is typically several micrometers, resulting in a limited field-of-voew (FOV) of several degrees. Here, we experimentally demonstrate an ultra-high-resolution LN hologram by using the laser poling technique. The minimal pixel size reaches 200 nm, and the FOV is extended above 120° in our experiments. The image distortions at large view angles are effectively suppressed through the Fourier transform. The FOV is further improved by combining multiple diffraction orders of SH fields. The ultimate FOV under our configuration is decided by a Fresnel transmission. Our results pave the way for expanding the applications of nonlinear holography to wide-view imaging and display.

Differences in change of post-operative antioxidant levels between laser-assisted lenticule extraction and femtosecond laser in situ keratomileusis.

To evaluate the change of total antioxidant capacity (TAC) and ascorbic acid (AA) between femtosecond laser in situ keratomileusis (FS-LASIK) and laser-assisted lenticule extraction (LALEX). A prospective non-randomized study was conducted, and 33 and 75 eyes that had undergone FS-LASIK or LALEX surgeries were enrolled, respectively. The tear films near corneal incisions were collected, and the concentrations of TAC and AA were determined. The generalized linear mixed model was adopted to calculate the adjusted odds ratio (aOR) with 95% confidence interval (CI) of TAC and AA between the two groups. The AA reduction was significant 1 month after the LALEX and FS-LASIK procedures (both p < 0.05), and the decrement in AA level was significantly larger in the FS-LASIK group compared to the LALEX group (p = 0.0002). In the subgroup analysis, the LALEX group demonstrated a lower decrement in TAC level in the individuals with dry eye disease (DED) than the FS-LASIK group (p = 0.0424), and the LALEX group demonstrated a significantly lower AA decrement in the participants with high myopia (p = 0.0165) and DED (p = 0.0043). The LALEX surgery causes lesser AA decrement compared to FS-LASIK surgery especially for the patients with DED.

Helical Micropillar Processed by One-Step 3D Printing for Solar Thermal Conversion.

Solar thermal utilization has broad applications in a variety of fields. Currently, maximizing the photo-thermal conversion efficiency remains a research hotspot in this field. The exquisite plant structures in nature have greatly inspired human structural design across many domains. In this work, inspired by the photosynthesis of helical grass, a HM type solar absorber made in graphene-based composite sheets is used for solar thermal conversion. The unique design promoted more effective solar energy into thermal energy through multiple reflections and scattering of solar photons. Notably, the Helical Micropillar (HM) is fabricated using a one-step projection 3D printing process based on a special 3D helical beam. As a result, the solar absorber's absorbance value can reach 0.83 in the 400-2500 nm range, and the surface temperature increased by ≈128.3% relative to the original temperature. The temperature rise rate of the solar absorber reached 22.4 °C min-1, demonstrating the significant potential of the HM in practical applications of solar thermal energy collection and utilization.

Printing 3D Metallic Structures in Porous Matrix.

The fabrication of metallic micro/nanostructures has great potential for advancing optoelectronic microdevices. Over the past decade, femtosecond laser direct writing (FsLDW) technology has played a crucial role in driving progress in this field. In this study, silica gel glass is used as a supporting medium, and FsLDW is employed to reduce gold and palladium ions using 7-Diethylamino-3-thenoylcoumarin (DETC) as a two-photon sensitizer, enabling the printing of conductive multilayered and 3D metallic structures. How the pore size of the silica gel glass affects the electrical conductivity of printed metal wires is systematically examined. This 3D printing method is versatile and offers expanded opportunities for applying metallic micro/nanostructures in optoelectronic devices.

Laser-Printed Photoanode: Femtosecond Laser-Induced Crystalline Phase Transformation of WO3 Nanorods for Space-Efficient and Flexible Thin-Film Solar Water-Splitting Cells.

Despite its potential for clean hydrogen harvesting, photoelectrochemical (PEC) water-splitting cells face challenges in commercialization, particularly related its harvesting performance and productivity at an industrial scale. Herein, a facile fabrication method of flexible thin-film photoanode for PEC water-splitting to overcome these limitations, based on laser processing technologies, is proposed. Laser-induced graphene, a carbon structure produced through direct laser writing carbonization (DLWC), plays a dual role: a flexible and stable current collector and a substrate for the hydrothermal synthesis of tungsten trioxide (WO3) nanorods (NRs). To facilitate water-splitting, a femtosecond-pulsed laser (fs laser) is focused on the WO3 NRs, converting their crystalline phase from pristine orthorhombic to monoclinic structure without thermal damage. With NiFe layered double hydroxide (LDH) catalyst, the flexible thin-film photoanode exhibits good PEC performance (1.46 mA cm-2 at 1.23 VRHE) and retains ≈90% of its performance after 3000 bending cycles. With its excellent mechanical properties, the flexible photoanode can be operated in various shapes with different curvatures, enabling space-efficient PEC water-splitting by loading larger photoanode within a given space. This study is expected to contribute to the advancement of large-scale solar water-splitting cells, introducing a new approach to enhance H2/O2 production and expand its application range.

Comparison of early changes in tear film protein profiles after small incision lenticule extraction (SMILE) and femtosecond LASIK (FS-LASIK) surgery.

BACKGROUND: Small incision lenticule extraction (SMILE) and femtosecond laser-assisted in situ keratomileusis (LASIK) are widely used surgical methods to correct myopia with comparable efficacy, predictability, and safety. We examined and compared the early changes of tear protein profiles after SMILE and FS-LASIK surgery in order to find possible differences in the initial corneal healing process. METHODS: SMILE operations for 26 eyes were made with Visumax femtosecond laser. In FS-LASIK surgery for 30 eyes, the flaps were made with Ziemer FEMTO LDV Z6 femtosecond laser and stromal ablation with Wavelight EX500 excimer laser. Tear samples were collected preoperatively, and 1.5 h and 1 month postoperatively using glass microcapillary tubes. Tear protein identification and quantification were performed with sequential window acquisition of all theoretical fragment ion spectra mass spectrometry (SWATH-MS). RESULTS: Immediately (1.5 h) after we found differences in 89 proteins after SMILE and in 123 after FS-LASIK operation compared to preoperative protein levels. Of these differentially expressed proteins, 48 proteins were common for both surgery types. There were, however, quantitative differences between SMILE and FS-LASIK. Upregulated proteins were mostly connected to inflammatory response and migration of the cells connected to immune system. One month after the operation protein expressions levels were returned to baseline levels with both surgical methods. CONCLUSIONS: Our study showed that immediate changes in protein profiles after SMILE and FS-LASIK surgeries and differences between the methods are connected to inflammatory process, and the protein levels quickly return to the baseline within 1 month. The differences in protein profiles between the methods are probably associated with the different size of the epithelial wound induced.

High throughput clogging free microfluidic particle filter by femtosecond laser micromachining.

In recent decades, driven by the needs of industry and medicine, researchers have been investigating how to remove carefully from the main flow microscopic particles or clusters of them. Among all the approaches proposed, crossflow filtration is one of the most attractive as it provides a non-destructive, label-free and in-flow sorting method. In general, the separation performance shows capture and separation efficiencies ranging from 70% up to 100%. However, the maximum flow rate achievable (µL/min) is still orders of magnitude away from those suitable for clinical or industrial applications mainly due to the low stiffness of the materials typically used. In this work, we propose an innovative hydrodynamic-crossflow hybrid filter geometry, buried in a fused silica substrate by means of the femtosecond laser irradiation followed by chemical etching technique. The material high stiffness combined with the accuracy of our manufacturing technique allows the 3D fabrication of non-deformable channels with higher aspect ratio posts, while keeping the overall device dimensions compact. The filter performance has been validated through experiments with both Newtonian (water-based solution of microbeads) and non-Newtonian fluids (blood), achieving separation efficiencies of up to 94% and large particles recovery rates of 100%, even at very high flow rates (mL/h).

Study on the biological properties of SMILE-derived corneal stromal lenticules after long-term cryopreservation in nutrient capsules.

PURPOSE: To investigate the long-term preservation effects of nutrient capsules on the physiological activity, collagen fiber structure and transmittance of corneal stromal lenticules derived from small incision lenticule extraction (SMILE). METHODS: A new nutrient capsule was constructed for long-term preservation of SMILE-derived corneal stromal lenticules. The lenticules were randomly divided into 99% anhydrous glycerol, and hydrogel nutrient capsules. After preserving for 1 year at -80 °C, lenticules were compared with fresh lenticules. The optical transmittance, tissue morphology, ultrastructure, cells activity and immunogenicity of the lenticules was detected and compared between different groups. RESULTS: The rate of apoptotic cells was significantly higher in the glycerol group compared with the nutrient capsule group (P < 0.0001). More viable cells were present in the lenticules after nutrient capsule preservation compared to the glycerol group (P = 0.0003). The mean transmittance of the lenticules in the glycerol group (50 ± 18%) was significantly lower (P = 0.0008) compared to the control group (75 ± 11%), and the lenticules transmittance of the nutrient capsule group (64 ± 15%) after long-term preservation was not significantly different (P = 0.23) compared to the control group. The structure of HE staining showed that the collagen fibers in the nutrient capsule group were arranged in parallel and neatly, and a few cavitation vesicles were visible inside the tissue. There was no significant difference in the number of lenticular collagen fibers in the nutritional capsule group compared to the fresh lenticule group (P = 0.06). HLA-DR, HLA-ABC, CD45, CD25 and CD69 expression was low in all groups of lenticules after preservation. CONCLUSIONS: Nutrient capsules can preserve lenticules for a long time and maintain the transmission structure and cells activity of lenticules.

Structural and chemical study of complex silver patterns additively manufactured by multi-photon reduction.

Multi-photon reduction (MPR) based on femtosecond laser makes rapid prototyping and molding in micro-nano scale feasible, but is limited in material selectivity due to lack of the understanding of the reaction mechanism in MPR process. In this paper, additively manufacturing of complex silver-based patterns through MPR is demonstrated. The effects of laser parameters, including laser pulse energies and scanning speeds, on the structural and chemical characteristics of the printed structures are systematically investigated. The results show that the geometric size of printed cubes deviates from the designed size further by increasing laser pulse energy or decreasing scanning speed. The reaction mechanism of MPR is revealed by studying the elemental composition and chemical structures of printed cubes. The evolution of Raman spectra upon the laser processing parameters suggests that the MPR process mainly includes two processes: reduction and decomposition. In the MPR process, silver ions are reduced and grow into particles by accepting the electrons from ethonal molecules; meanwhile carboxyl groups in polyvinylpyrrolidone are decomposed and form amorphous carbon that is attached on the surface of silver particles. The conductivity of silver wires fabricated by MPR reaches 2 × 105S m-1and stays relatively constant as varying their cross section area, suggesting excellent electrical conduction. The understanding of the MPR process would accelerate the development of MPR technology and the implementation of MPR in micro-electromechanical systems could therefore be envisioned.

Critical pulse in multi-shot femtosecond laser ablation on metallic surfaces.

Thermal effect remains a thorny issue for femtosecond-laser surface engineering and nanostructuring on metallic targets with high pulse energies or high repetition rates, which needs to be paid adequate attentions. Herein, we have experimentally investigated the heat diffusion and accumulations during single-shot and multi-shot femtosecond laser ablation on metallic surfaces. We have for the first time observed a novel phenomenon that the thermal effect was intensified abruptly when the laser-pulse number goes over a threshold (approximately between 10 and 20 for aluminum alloy with laser fluence of 6 J cm-2), accompanied with a dramatic reduction of ablated depth and complicated plasma dynamics. Based on both optical and thermodynamic analysis, we introduced a defocusing-dominated plasma-assistant model for this abnormal thermal effect. This work explored the critical experimental parameters for femtosecond-laser surface modification and processing in micro-scale engineering applications.

Specificity of Photochemical Energy Conversion in Photosystem I from the Green Microalga Chlorella ohadii.

Primary excitation energy transfer and charge separation in photosystem I (PSI) from the extremophile desert green alga Chlorella ohadii grown in low light were studied using broadband femtosecond pump-probe spectroscopy in the spectral range from 400 to 850 nm and in the time range from 50 fs to 500 ps. Photochemical reactions were induced by the excitation into the blue and red edges of the chlorophyll Qy absorption band and compared with similar processes in PSI from the cyanobacterium Synechocystis sp. PCC 6803. When PSI from C. ohadii was excited at 660 nm, the processes of energy redistribution in the light-harvesting antenna complex were observed within a time interval of up to 25 ps, while formation of the stable radical ion pair P700+A1- was kinetically heterogeneous with characteristic times of 25 and 120 ps. When PSI was excited into the red edge of the Qy band at 715 nm, primary charge separation reactions occurred within the time range of 7 ps in half of the complexes. In the remaining complexes, formation of the radical ion pair P700+A1- was limited by the energy transfer and occurred with a characteristic time of 70 ps. Similar photochemical reactions in PSI from Synechocystis 6803 were significantly faster: upon excitation at 680 nm, formation of the primary radical ion pairs occurred with a time of 3 ps in ~30% complexes. Excitation at 720 nm resulted in kinetically unresolvable ultrafast primary charge separation in 50% complexes, and subsequent formation of P700+A1- was observed within 25 ps. The photodynamics of PSI from C. ohadii was noticeably similar to the excitation energy transfer and charge separation in PSI from the microalga Chlamydomonas reinhardtii; however, the dynamics of energy transfer in C. ohadii PSI also included slower components.

A new technique to implant intracorneal ring-segments from the perilimbal region: one-year prospective pilot study report.

BACKGROUND: Recently a new surgical technique for intracorneal ring-segments (ICRS) assisted by femtosecond laser (FSL) called ByLimB was developed, involving the creation of the incision from a paralimbic region. This study aims to evaluate the safety and efficacy of the ByLimb technique following one year of follow-up. METHODS: A prospective, single-center study was conducted at the Zaldivar Institute in Buenos Aires, Argentina. Keratoconus patients with indication for ICRS-FSL assisted procedure, operated with the ByLimb technique were included. By using the ByLimb technique, the ICRS are placed without affecting the tunnel's roof, and the end of the ICRS is always away from the incision area. Visual acuity, topographic astigmatism, and the occurrence of complications were evaluated. Safety index was the main outcome and efficacy indes was a complimentary outcome. RESULTS: A total of 17 eyes completed the 12-month follow-up period. The safety index was 1.10 (mean postoperative corrected distance visual acuity (CDVA) in decimal: 0.76/preoperative CDVA: 0.69), while the efficacy index was 0.89 (mean postoperative uncorrected distance visual acuity UDVA in decimal: 0.62/preoperative CDVA: 0.69). Mean preoperative astigmatism was 5.3 ± 2.3, decreasing twelve months after surgery at 2.1 ± 1.2 (p < 0.001). No eye loss lines of vision and no intraoperative complications were observed. During the first month after surgery, an improper positioning of the ICRS based on topographic assessment was detected in five cases. A second procedure was performed, which consisted of opening the incision and introducing a Sinsky hook, through which the ICRS was mobilized and placed in its correct position. No incisional alterations, signs of infection, anterior segment anomalies, or fundus alterations were observed. CONCLUSION: FSL-assisted ICRS implantation through the perilimbal region has demonstrated an adequate safety index one year post-surgery. Additionally, this technique has facilitated accurate realignment of ICRS during secondary surgical interventions within one-month post-surgery. While the current findings are promising, continued follow-up of these cases is warranted.

Comparison of short-term clinical outcomes of a diffractive trifocal intraocular lens with phacoemulsification and femtosecond laser assisted cataract surgery.

PURPOSE: To evaluate short-term visual and refractive outcomes after implantation of a diffractive trifocal intraocular lens (IOL) in cataract patients with phacoemulsification (PHACO) and femtosecond laser assisted cataract surgery (FLACS). SETTING: Department of Ophthalmology, Shanghai Aier Eye Hospital, China. DESIGN: A retrospective, observational study. METHODS: Patients who underwent cataract surgery combined with Acrysoft IQ PanOptix trifocal IOL implantation were enrolled and divided into three groups: PHACO group, LAstig-FLACS group (astigmatism less then 1D) and HAstig-FLACS group (astigmatism more than 1D). Logarithm of the minimum angle of resolution (logMAR) visual acuity of uncorrected distance (UDVA), intermediate (UIVA), near visual (UNVA), defocus curve, surgically induced astigmatism (SIA) were evaluated in 1 months postoperatively and wavefront aberrations were evaluated in 6 months. RESULTS: 101 eyes of 60 patients were included with 31 eyes in PHACO group, 45 eyes in LAstig-FLACS group and 25 eyes in HAstig-FLACS group. Significant difference was found of internal Strehl Ratio (SR) between PHACO and LAstig-FLACS group (P = 0.026). In PHACO group, 79.31%, 86.21%, 72.41% of eyes gain visual acuity LogMAR 0.1 or more in UDVA, UIVA and UNVA, while 83.72%, 93.02%, 93.02% of those in LAstig-FLACS group and 92.00%, 84.00%, 76.00% in HAstig-FLACS group. CONCLUSIONS: Panoptix diffractive trifocal IOL provides satisfied visual outcome in no matter FLACS or PHACO. Besides, trifocal IOL implantation via FLACS can provide a better accumulative visual acuity outcome at all distance than PHACO in 1 month. Femtosecond laser assisted limbal relaxing incisions (FLLRIs) is an excellent way to reduce a patient's corneal astigmatism.