Self-propelled Leidenfrost droplets on femtosecond-laser-induced surface with periodic hydrophobicity gradient

The controllable transfer of droplets on the surface of objects has a wide application prospect in the fields of microfluidic devices,fog collection and so on.The Leidenfrost effect can be utilized to significantly reduce motion resistance.However,the use of 3D structures limits the widespread application of self-propulsion based on Leidenfrost droplets in microelectromechanical system.To manipulate Leidenfrost droplets,it is necessary to create 2D or quasi-2D geometries.In this study,femtosecond laser is applied to fabricate a surface with periodic hydrophobicity gradient(SPHG),enabling directional self-propulsion of Leidenfrost droplets.Flow field analysis within the Leidenfrost droplets reveals that the vapor layer between the droplets and the hot surface can be modulated by the SPHG,resulting in directional propulsion of the inner gas.The viscous force between the gas and liquid then drives the droplet to move.

High performance micromachining of sapphire by laser induced plasma assisted ablation(LIPAA)using GHz burst mode femtosecond pulses

GHz burst-mode femtosecond(fs)laser,which emits a series of pulse trains with extremely short intervals of several hundred picoseconds,provides distinct characteristics in materials processing as compared with the conventional irradiation scheme of fs laser(single-pulse mode).In this paper,we take advantage of the moderate pulse interval of 205 ps(4.88 GHz)in the burst pulse for high-quality and high-efficiency micromachining of single crystalline sapphire by laser induced plasma assisted ablation(LIPAA).Specifically,the preceding pulses in the burst generate plasma by ablation of copper placed behind the sapphire substrate,which interacts with the subsequent pulses to induce ablation at the rear surface of sapphire substrates.As a result,not only the ablation quality but also the ablation efficiency and the fabrication resolution are greatly improved compared to the other schemes including single-pulse mode fs laser direct ablation,single-pulse mode fs-LIPAA,and nanosecond-LIPAA.

Evaluation of the Clinical Efficacy of Full Femtosecond Laser Surgery in the Treatment of Myopia

Objective:To evaluate the clinical effect of full femtosecond laser surgery in the treatment of myopia patients.Methods:120 myopia patients admitted to our hospital from January 2022 to June 2023 were selected.According to the random number table method,60 patients in the observation group underwent full femtosecond laser surgery,and 60 patients in the control group underwent femtosecond laser-assisted in situ keratomileusis(FS-LASIK)surgery.The clinical effects of the two groups were compared.Results:10 days postoperatively and 6 months after operation,the visual acuity level of the observation group was higher than that of the control group,the postoperative corneal asphericity coefficient and corneal full-thickness were lower than those of the control group,and the total effective rate 6 months after operation was higher than that of the control group(P<0.05).Conclusion:Full femtosecond laser surgical treatment can improve the postoperative visual acuity of patients with myopia,enhance the corneal asphericity coefficient(Q)and corneal full-thickness,and exert significant clinical effects.

Triboelectric‘electrostatic tweezers'for manipulating droplets on lubricated slippery surfaces prepared by femtosecond laser processing

The use of‘Electrostatic tweezers'is a promising tool for droplet manipulation,but it faces many limitations in manipulating droplets on superhydrophobic surfaces.Here,we achieve noncontact and multifunctional droplet manipulation on Nepenthes-inspired lubricated slippery surfaces via triboelectric electrostatic tweezers(TETs).The TET manipulation of droplets on a slippery surface has many advantages over electrostatic droplet manipulation on a superhydrophobic surface.The electrostatic field induces the redistribution of the charges inside the neutral droplet,which causes the triboelectric charged rod to drive the droplet to move forward under the electrostatic force.Positively or negatively charged droplets can also be driven by TET based on electrostatic attraction and repulsion.TET enables us to manipulate droplets under diverse conditions,including anti-gravity climb,suspended droplets,corrosive liquids,low-surface-tension liquids(e.g.ethanol with a surface tension of 22.3 mN·m^(-1)),different droplet volumes(from 100 nl to 0.5 ml),passing through narrow slits,sliding over damaged areas,on various solid substrates,and even droplets in an enclosed system.Various droplet-related applications,such as motion guidance,motion switching,droplet-based microreactions,surface cleaning,surface defogging,liquid sorting,and cell labeling,can be easily achieved with TETs.

Effect of sample temperature on femtosecond laser ablation of copper

We conduct an experimental study supported by theoretical analysis of single laser ablating copper to investigate the interactions between laser and material at different sample temperatures,and predict the changes of ablation morphology and lattice temperature.For investigating the effect of sample temperature on femtosecond laser processing,we conduct experiments on and simulate the thermal behavior of femtosecond laser irradiating copper by using a two-temperature model.The simulation results show that both electron peak temperature and the relaxation time needed to reach equilibrium increase as initial sample temperature rises.When the sample temperature rises from 300 K to 600 K,the maximum lattice temperature of the copper surface increases by about 6500 K under femtosecond laser irradiation,and the ablation depth increases by 20%.The simulated ablation depths follow the same general trend as the experimental values.This work provides some theoretical basis and technical support for developing femtosecond laser processing in the field of metal materials.

High-performance liquid metal electromagnetic actuator fabricated by femtosecond laser

Small-scale electromagnetic soft actuators are characterized by a fast response and simplecontrol,holding prospects in the field of soft and miniaturized robotics.The use of liquid metal(LM)to replace a rigid conductor inside soft actuators can reduce the rigidity and enhance the actuation performance and robustness.Despite research efforts,challenges persist in the flexible fabrication of LM soft actuators and in the improvement of actuation performance.To address these challenges,we developed a fast and robust electromagnetic soft microplate actuator based on a laser-induced selective adhesion transfer method.Equipped with unprecedentedly thin LM circuit and customized low Young’s modulus silicone rubber(1.03 kPa),our actuator exhibits an excellent deformation angle(265.25?)and actuation bending angular velocity(284.66 rad·s^(-1)).Furthermore,multiple actuators have been combined to build an artificial gripper with a wide range of functionalities.Our actuator presents new possibilities for designing small-scaleartificial machines and supports advancements in ultrafast soft and miniaturized robotics.

Clinical efficacy of femtosecond laser-assisted phacoemulsification in diabetic cataract patients

BACKGROUND Diabetic patients with cataracts encounter specific difficulties during cataract surgery due to alterations in microcirculation,blood supply,metabolism,and the microenvironment.Traditional phacoemulsification may not fully tackle these issues,especially in instances with substantial preoperative astigmatism.The utilization of femtosecond laser-assisted phacoemulsification,in conjunction with Toric intraocular lens(IOL)implantation,offers a potentially more efficient strategy.This research seeks to evaluate the efficacy and possible complications of this approach in diabetic cataract patients.AIM To investigate the clinical efficacy and complications of femtosecond laser-assisted phacoemulsification combined with Toric IOL implantation in diabetic cataract patients,comparing it with traditional phacoemulsification methods.METHODS This retrospective study enrolled 120 patients with diabetes cataract from May 2019 to May 2021.The patients were divided into two groups:the control group underwent traditional phacoemulsification and Toric IOL implantation,while the treatment group received Len Sx femtosecond laser-assisted treatment.Outcome measures included naked eye vision,astigmatism,high-level ocular phase difference detection,clinical efficacy,and complication.RESULTS There were no significant preoperative differences in astigmatism or naked eyesight between the two groups.However,postoperative improvements were observed in both groups,with the treatment group showing greater enhancements in naked eye vision and astigmatism six months after the procedure.High-level corneal phase difference tests also indicated significant differences in favor of the treatment group.CONCLUSION This study suggests that femtosecond laser-assisted phacoemulsification combined with Toric IOL implantation appears to be more effective in enhancing postoperative vision in diabetic cataract patients compared to traditional methods offering valuable insights for clinical practice.

Generation and regulation of electromagnetic pulses generated by femtosecond lasers interacting with multitargets

Ultrashort and powerful laser interactions with a target generate intense wideband electromagnetic pulses(EMPs).In this study,we report EMPs generated by the interactions between petawatt(30 fs,1.4×10^(20) W/cm^(2))femtosecond(fs)lasers with metal flat,plastic flat,and plastic nanowire-array(NWA)targets.Detailed analyses are conducted on the EMPs in terms of their spatial distribution,time and frequency domains,radiation energy,and protection.The results indicate that EMPs from metal targets exhibit larger amplitudes at varying angles than those generated by other types of targets and are enhanced significantly for NWA targets.Using a plastic target holder and increasing the laser focal spot can significantly decrease the radiation energy of the EMPs.Moreover,the composite shielding materials indicate an effective shielding effect against EMPs.The simulation results show that the NWA targets exert a collimating effect on thermal electrons,which directly affects the distribution of EMPs.This study provides guidance for regulating EMPs by controlling the laser focal spot,target parameters,and target rod material and is beneficial for electromagnetic-shielding design.

Corneal astigmatic outcomes after femtosecond laser-assisted cataract surgery combined with surface penetrating arcuate keratotomies

AIM:To evaluate corneal astigmatic outcomes of femtosecond laser-assisted arcuate keratotomies(FAKs)combined with femtosecond-laser assisted cataract surgery(FLACS)over 12mo follow-up.METHODS:Totally 145 patients with bilateral cataracts and no ocular co-morbidities were recruited to a singlecentre,single-masked,prospective randomized controlled trial(RCT)comparing two monofocal hydrophobic acrylic intraocular lenses.Eyes with corneal astigmatism(CA)of>0.8 dioptres(D)received unpaired,unopened,surface penetrating FAKs at the time of FLACS.Visual acuity,subjective refraction and Scheimpflug tomography were recorded at 1,6,and 12mo.Alpins vectoral analyses were performed.RESULTS:Fifty-one patients(61 eyes),mean age 68.2±9.6y[standard deviation(SD)],received FAKs.Sixty eyes were available for analysis,except at 12mo when 59 attended.There were no complications due to FAKs.Mean pre-operative CA was 1.13±0.20 D.There was a reduction of astigmatism at all post-operative visits(residual CA 1mo:0.85±0.42 D,P=0.0001;6mo:0.86±0.35 D,P=0001;and 12mo:0.90±0.39,P=0.0001).Alpins indices remained stable over 12mo.Overall,the cohort was under-corrected at all time points.At 12mo,61%of eyes were within±15 degrees of pre-operative astigmatic meridian.CONCLUSION:Unpaired unopened penetrating FAKs combined with on-axis phacoemulsification are safe but minimally effective.CA is largely under-corrected in this cohort using an existing unmodified nomogram.The effect of arcuate keratotomies on CA remained stable over 12mo.

Hot electron electrochemistry at silver activated by femtosecond laser pulses

A silver microelectrode with a diameter of 30μm in an aqueous K_(2)SO_(4) electrolyte was irradiated with 55 fs and 213 fs laser pulses.This caused the emission of electrons which transiently charged the electrochemical double layer.The two applied pulse durations were significantly shorter than the electron-phonon relaxation time.The laser pulse durations had negligible impact on the emitted charge,which is incompatible with multiphoton emission.On the other hand,the ob-served dependence of emitted charge on laser fluence and electrode potential supports the thermionic emission mechanism.

Microsphere femtosecond laser sub-50 nm structuring in far field via non-linear absorption

Creation of arbitrary features with high resolution is critically important in the fabrication of nano-optoelectronic devices.Here,sub-50 nm surface structuring is achieved directly on Sb2S3 thin films via microsphere femtosecond laser irradi-ation in far field.By varying laser fluence and scanning speed,nano-feature sizes can be flexibly tuned.Such small patterns are attributed to the co-effect of microsphere focusing,two-photons absorption,top threshold effect,and high-repetition-rate femtosecond laser-induced incubation effect.The minimum feature size can be reduced down to~30 nm(λ/26)by manipulating film thickness.The fitting analysis between the ablation width and depth predicts that the feature size can be down to~15 nm at the film thickness of~10 nm.A nano-grating is fabricated,which demonstrates desirable beam diffraction performance.This nano-scale resolution would be highly attractive for next-generation laser nano-lithography in far field and in ambient air.

Crack-free high-aspect ratio holes in glasses by top–down percussion drilling with infrared femtosecond laser GHz-bursts

We report novel results on top-down percussion drilling in different glasses with femtosecond laser GHz-bursts.Thanks to this particular regime of light–matter interaction,combining non-linear absorption and thermal cumulative effects,we obtained crack-free holes of aspect ratios exceeding 30 in sodalime and 70 in fused silica.The results are discussed in terms of inner wall morphology,aspect ratio and drilling speed.

Symmetrical femtosecond laser arc incision in correcting corneal astigmatism in cataract patients

AIM:To evaluate the effect of symmetrical arc incision correcting corneal astigmatism in femtosecond laserassisted phacoemulsification(FLACS).METHODS:This study enrolled patients with cataract combined with regular corneal astigmatism of>0.75 D,who underwent FLACS.Symmetrical arc incision was set at 8 mm diameter and 85%depth.The follow-up time was 3-24mo(4.92±3.49mo).Pentacam recorded the corneal astigmatism and higher-order aberration at pre-operation and post-operation.The changes in corneal astigmatism were analyzed by Alpins method.The correlation of astigmatism type,age,corneal horizontal diameter,corneal thickness,arc incision length,and correction index(CI)was analyzed,and the residual corneal astigmatism was compared with the residual whole eye astigmatism.RESULTS:Totally 79 patients(102 eyes)were enrolled,10 patients had corneal epithelial injury,1 patient occurred corneal epithelial hyperplasia.The corneal astigmatism was 1.23±0.38 D pre-operation,and decreased to 0.76±0.39 D post-operation(t=10.146,P=0.000).Corneal high-order aberration was 0.17±0.08μm pre-operation and 0.24±0.11μm post-operation(t=-5.186,P=0.000).The residual corneal astigmatism and residual whole eye astigmatism were no significant difference(t=-0.347,P=0.729).Using Alpin’s method,the following were determined:target-induced astigmatism(TIA)=1.23±0.38 D,surgeryinduced astigmatism(SIA)=0.77±0.45 D,difference vector(DV)=0.77±0.39 D,and CI=0.54±0.28.Age,astigmatism size,corneal horizontal diameter,corneal thickness,and arc incision length were not correlated with CI.The CI for against the rule astigmatism(ATR)was better than that for with the rule astigmatism(WTR;P=0.001).CONCLUSION:Femtosecond laser-assisted astigmatic keratotomy has better CI of ATR,but increase higher-order corneal aberration.CI is not ideal,it’s not a perfect choice if we pursue ideal correction effect.

Periodic transparent nanowires in ITO film fabricated via femtosecond laser direct writing

This paper reports the fabrication of regular large-area laser-induced periodic surface structures(LIPSSs)in indium tin oxide(ITO)films via femtosecond laser direct writing focused by a cylindrical lens.The regular LIPSSs exhibited good properties as nanowires,with a resistivity almost equal to that of the initial ITO film.By changing the laser fluence,the nanowire resistances could be tuned from 15 to 73 kΩ/mm with a consistency of±10%.Furthermore,the average transmittance of the ITO films with regular LIPSSs in the range of 1200-2000 nm was improved from 21%to 60%.The regular LIPSS is promising for transparent electrodes of nano-optoelectronic devices-particularly in the near-infrared band.

GHz bursts in MHz burst(BiBurst) enabling high-speed femtosecond laser ablation of silicon due to prevention of air ionization

For the practical use of femtosecond laser ablation, inputs of higher laser intensity are preferred to attain high-throughput material removal. However, the use of higher laser intensities for increasing ablation rates can have detrimental effects on ablation quality due to excess heat generation and air ionization. This paper employs ablation using BiBurst femtosecond laser pulses, which consist of multiple bursts(2 and 5 bursts) at a repetition rate of 64 MHz, each containing multiple intra-pulses(2–20 pulses) at an ultrafast repetition rate of 4.88 GHz, to overcome these conflicting conditions. Ablation of silicon substrates using the BiBurst mode with 5 burst pulses and 20 intra-pulses successfully prevents air breakdown at packet energies higher than the pulse energy inducing the air ionization by the conventional femtosecond laser pulse irradiation(single-pulse mode). As a result, ablation speed can be enhanced by a factor of23 without deteriorating the ablation quality compared to that by the single-pulse mode ablation under the conditions where the air ionization is avoided.

Small incision lenticule extraction and femtosecond-assisted laser in situ keratomileusis in patients with deep corneal opacity:case series

AIM:To report the safety,efficacy,and accuracy of small-incision lenticule extraction(SMILE)or femtosecondassisted laser in situ keratomileusis(FS-LASIK)for the correction of myopia or myopic astigmatism in patients with deep corneal opacity denoted by anterior segment optical coherence tomography(AS-OCT).METHODS:Four patients with monocular corneal opacity(3 due to mechanical injury,1 due to a firecracker wound)were recruited and treated with refractive surgery(3 for SMILE,1 for FS-LASIK combined with limbal relaxing incision(LRI).Preoperative ocular manifestations,surgical details,postoperative visual outcomes,corneal opacity parameters,and corneal topography were analyzed.RESULTS:Preoperatively,spherical diopter ranged from-3.0 D to-4.75 D with cylinder ranging from-0.75 to-5.0 D,and corrected distance visual acuity(CDVA)ranging from 20/25 to 20/20.One eye’s corneal opacity was located in the central zone and three were in the mid-peripheral optical zone.Three patients underwent uneventful SMILE in both eyes,whilst one patient underwent FS-LASIK for high astigmatism in both eyes and LRI in the right eye.CDVA of the eye with corneal opacity ranged from 20/22to 20/20 one to six weeks postoperatively.Two patients achieved better CDVA and no patients lost Snellen lines.The postoperative diopter was within±0.75 D for all eyes.Significant edema existed above the corneal opacity in one eye and dissipated soon.No eccentric corneal topography or morphological anomaly of the corneal cap or flap was observed.CONCLUSION:The cases demonstrate that SMILE or FS-LASIK is safe and effective to treat myopic astigmatism combined with deep corneal opacity lesions after comprehensive preoperative evaluation and appropriate candidate selection.FS-LASIK combined with LRI is also sufficient for correcting high astigmatism due to corneal scarring.

Comparison of visual performance with iTrace analyzer following femtosecond laser-assisted cataract surgery with bilateral implantation of two different trifocal intraocular lenses

AIM:To compare the postoperative binocular visual performance with an iTrace analyzer following femtosecond laser-assisted cataract surgery(FLACS)combined with bilateral implantation of two different types of diffractive trifocal intraocular lenses(IOL).METHODS:During this retrospective observational study,patients who received bilateral FLACS combined with implantation of two different types of diffractive trifocal IOLs were evaluated.According to the IOLs’different types and design,the patients were divided into AT LISA tri839MP group(tri839 group)and AcrySof PanOptix TFNT00 group(TFNT group).Study parameters included preoperative and postoperative uncorrected distance visual acuity(UDVA)at 5 m,uncorrected near visual acuity(UNVA)at 30 cm and 40 cm,uncorrected intermediate visual acuity(UIVA)at 60 cm and 80 cm,postoperative refractive status,objective visual qualities and total high order aberrations(HOAs)postoperatively.The postoperative complications were also recorded.RESULTS:Totally 56 eyes of 28 patients(tri839 group,n=26;TFNT group,n=30)were included.Preoperative baseline characteristics between groups were not statistically significantly different.UDVA was not significantly different between groups except for 1wk follow-up due to the postoperative corneal edema.TFNT group showed statistically significant better UNIA at 60 cm than tri839 group at the 1wk(0.05±0.19 vs 0.15±0.10 logMAR,P=0.013),1mo(0.05±0.12 vs 0.15±0.09 logMAR,P=0.001)and 3mo(0.04±0.12 vs 0.15±0.11 logMAR,P=0.001)follow-up,while tri839 group showed statistically significant better UNIA at 80 cm than TFNT group at the 1d(0.14±0.15 vs 0.20±0.14 logMAR,P=0.041)and 1mo(0.09±0.07 vs 0.14±0.10 logMAR,P=0.042)follow-up.Postoperative refractive status showed stable at every visit.Modulated transfer function(MTF)values and strehl ratio(SR)values were improved and HOAs were lower significantly after surgery.CONCLUSION:FLACS with bilateral implantations of both tri839 and TFNT00 can achieve satisfactory natural whole-course vision,high postoperative refractive stability and good visual quality but without significantly difference.iTrace aberration instrument can accurately evaluate the visual quality under different status.

Comparative study of functional optical zone:small incision lenticule extraction versus femtosecond laser assisted excimer laser keratomileusis

AIM:To investigate the size of functional optical zone(FOZ)after small incision lenticule extraction(SMILE)versus femtosecond laser assisted excimer laser keratomileusis(FS-LASIK)for myopia correction and potential associated factors for FOZ.METHODS:A total of 133 patients who received corneal refractive surgery in our hospital between November 2018 and July 2021 were retrospectively enrolled.There were 63 patients(123 eyes)in SMILE group and 70patients(139 eyes)in FS-LASIK group.The size of FOZ was measured using Pentacam 3-dementional anterior segment analyzer before and 3mo after surgery,so as to analyze postoperative achieved functional optical zone(AFOZ)and its contributing parameters.RESULTS:When planned functional optical zone(PFOZ)was 6.5 mm for both groups,AFOZ was 1.45±0.27 and 1.67±0.25 mm smaller than preoperative FOZ in SMILE group and FS-LASIK group 3mo after surgery.AFOZ in SMILE group was significantly larger than that in FS-LASIK group(P<0.001).Variation of FOZ was negatively correlated with preoperative spherical equivalent(SE)and positively correlated with variation of mean keratometry value(△Km),variation of spherical aberration(△SA),and variation of Q-value(△Q,all P<0.001)in both groups.Multiple variable linear regression equations were△FOZ=1.354-0.1×pre-SE+0.336×△Q+1.462×△SA in SMILE group and△FOZ=1.512+0.137×△Q+0.468×△SA in FS-LASIK group.CONCLUSION:AFOZ is significantly smaller than preoperative FOZ in both SMILE and FS-LASIK groups.With the same PFOZ,larger AFOZ is achieved in SMILE group than in FS-LASIK group.

Application of femtosecond laser in assisted cataract after ICL implantation with different vault

Dear Editor,We are writing this letter to report two unusual cases of femtosecond laser-assisted cataract surgery(FLACS)in two ICL-implanted patients with significant different vault.FLACS has been confirmed by accumulating evidence to improve the safety and precision of surgery from common cases to complicated cases in treating cataracts[1-3].Implantable collamer lens(ICL)implantation possesses a good performance in its predictability,reversibility,and the rapid visual recovery.

Numerical Simulation for the Efficiency of the Produced Terahertz Radiation by Two Femtosecond Laser Pulses: Above-Threshold-Ionization

The tunneling ionization (TI) is the most dominated ionization process in the production of terahertz radiation by two femtosecond lasers, although its validity above the ionization threshold of some gases is uncertain. In the present research, we employ a 1D fluid code to simulate the efficiency of the produced terahertz radiation by two femtosecond laser beams in air plasma. Two ionization models in the context of the TI process which are the Ammosov-Delone-Krainov (ADK) for noble gases and its developed molecular ADK (MO-ADK) model for molecular gases are intrinsically used to conduct this study. The main target of the present research is to examine the validity of these models Above-Threshold-Ionization (ATI) of these gases. For this purpose, we simulated the ionization rate and the power spectrum of the produced radiation, in addition we numerically evaluated the efficiency of the produced radiation as function of the input beams intensity at particular energy fraction factor, relative phase and initial pulse duration of these beams. These calculations conducted for a selected noble gas at varying energy levels and a chosen molecular air plasma gas at different quantum numbers. Numerical results near and above the ionization threshold of the selected gases have clarified that the ADK and MO-ADK model are successful valid to study the efficiency of the produced THz radiation at low energy levels and small quantum numbers of the selected gases, meanwhile, with any further increase in the energy level and the quantum number values of these gases, both of the ADK and MO-ADK are failed to correctly analyze the efficiency process and estimate its fundamental parameters.