Selective Laser Ablation Research Articles

Label-Free Exosome Analysis by Surface-Enhanced Raman Scattering Spectroscopy with Laser-Ablated Silver Nanoparticle Substrate.

Early diagnostics of breast cancer is crucial to reduce the risk of cancer metastasis and late relapse. Exosome, which contains distinct information of its origin, can be the target object as a liquid biopsy. However, its low sensitivity and inadequate diagnostic tools interfere with the point-of-care testing (POCT) of the exosome. Recently, Surface-enhanced Raman Scattering (SERS) spectroscopy, which amplifies the Raman scattering, has been proved as a promising tool for exosome detection. However, the fabrication process of SERS probe or substrate is still inefficient and far from large-scale production. This study proposes rapid and label-free detection of breast cancer-derived exosomes by statistical analysis of SERS spectra using silver-nanoparticle-based SERS substrate fabricated by selective laser ablation and melting (SLAM). Employing silver nanowires and optimizing laser process parameters enable rapid and low-energy fabrication of SERS substrate. The functionalities including sensitivity, reproducibility, stability, and renewability are evaluated using rhodamine 6G as a probe molecule. Then, the feasibility of POCT is examined by the statistical analysis of SERS spectra of exosomes from malignant breast cancer cells and non-tumorigenic breast epithelial cells. The presented framework is anticipated to be utilized in other biomedical applications, facilitating cost-effective and large-scale production performance.

High-resolution dynamic thermal programming platform based on micro thermoelectric device assisted by laser integrated manufacturing

Thermoelectric devices (TEDs) exhibit much application potential in thermal camouflage and encrypted display recently, requiring that TEDs possess large responsivity, high resolution and rapid response with flexible configuration design, which are hardly realized by the traditional complex fabrication process. In this work, an innovative laser integrated manufacturing technology including double-side-printing selective laser melting (D-SLM) and selective laser ablation (SLA) is developed for the construction of the dynamic thermal platform based on micro TEDs. Through experimentally determining the laser process window assisted by external temperature field regulation, a flat p-type film can be directly transformed from n-type Bi2Te3 film by D-SLM. Thus, high-precision p-n patterns without metal joints are obtained from a single locally modified film, whose thermoelectric properties are further boosted by increasing energy density and introducing a post-annealing process. Then, a dynamic thermal platform with designable shapes and small dimensions can be fabricated rapidly whose working principle is also demonstrated. The thermal platform with 4*4 arrays exhibits imaging function with a pixel size of 2 mm×2 mm, a temperature difference of ∼3 K, and a fast response time of 0.143 s. This work offers an exciting yet effective approach to fabricating TEDs for dynamic thermal programmable information displays.

Laser layered scanning strategy for fractal Ag mesh transparent conductive electrodes using selective laser ablation and its application to transparent heaters

In this study, 800 nm-thick silver (Ag) films were deposited on glass substrates via radio frequency (RF) magnetron sputtering. Based on a laser layered scanning strategy during selective laser ablation (SLA), periodic (1–4) and pattern-combined (4–9) fractal Ag mesh transparent conductive electrodes (TCEs) with two layered mesh thicknesses were prepared to investigate the influences of mesh thickness matching on their optical and electrical properties. The results revealed that constructing the layered mesh thickness by selectively removing the thick Ag layer could enhance the TCE optical transmittance without greatly sacrificing its electrical conductivity. The two kinds of fractal layered Ag mesh TCEs with mesh thickness matching of 800 nm: 500 nm were confirmed to have high performance uniformity, and respectively exhibited the highest figure of merit value of 16.03 × 10–2 Ω−1 and 15.23 × 10–2 Ω−1. Moreover, the best periodic (1–4) fractal layered Ag mesh TCE was adopted to fabricate a transparent heater (TH), which exhibited excellent heating performance (a maximum temperature of 143.1 ℃ with a response time of ∼ 80 s under a lower voltage of 1.3 V), switching cycle stability and deicing ability. The sheet resistance stability of the TH under different test conditions was also demonstrated. This work has a certain reference value for the preparation of high-performance TCEs and THs.

Laser-textured biomimetic copper leaf with structural-wettability dual gradient for efficient fog harvesting

Water collection has gradually become research hot topic owing to its potential for alleviating water shortages in arid areas. To date, numerous artificial materials with hierarchical structure have been fabricated to improve water-collecting efficiency. Here, a multi-bioinspired fog-harvesting artificial Cu-Leaf, deriving from Leaf skeletons, Namib desert beetle, and Cactus spines, is fabricated by ultrafast laser selective ablation, chemical etching and chemical vapor deposition, which achieve efficient water-collecting by combining fog capture, droplet growing and directional transportation together. The four-level wedge-shaped tracks of Cu-Leaf skeleton and its wetting property were finely adjusted and their correlations with the fog-harvesting capability were systematically studied. Force analysis related to fog capture, droplet growing and the droplet directional transportation on the hydrophobic/hydrophilic patterned skeleton surfaces have been highlighted. The optimal biomimetic Cu-Leaf performed superior fog-harvesting property with harvesting rate of 544.03 mg/h cm2, which is 2.5 times that of the original Cu sheet. Moreover, we designed an integrated fog-harvesting device (FHD) that could realize the dynamic fog-harvesting and efficient water storage. Therefore, this work enhances the understanding of the fundamental research and provides valuable strategy for design and preparation of sustainable and efficient fog harvesting systems.

Selective laser ablation for in situ fabrication of enclosed channel porous-media microfluidic analytical devices.

This work describes a new method for fabrication of enclosed channel porous-media microfluidic analytical devices using selective laser ablation. Microfluidic structures can be readily produced inside the enclosed devices within two fabrication steps. A sheet of porous material was first sandwiched and bonded between two sheets of polymeric film. The porous substrate inside the film layers was then selectively ablated using a laser cutter to create hollow barriers for microfluidic channels. Selective ablation of only the porous layer was achieved because the porous substrate layer is susceptible to ablation by the laser beam, whereas the film layer is resistant to laser ablation due to its light transmission properties. This selective laser ablation processing is not limited by laser type. As a proof-of-concept, two different laser systems, a 10.6 μm CO2 laser and a 455 nm diode laser, were employed for this purpose. A variety of porous materials, including cellulose, nitrocellulose, and glass microfiber, were combined with a wide variety of polymeric films to fabricate enclosed microfluidic devices. The developed method is versatile; depending on material combination and number of layers of materials in the devices, enclosed microfluidic devices with 2D, passive 3D, or compression-activated 3D fluid flow can be created. Quantitative assays for albumin, glucose, and cholesterol in human serum performed using devices produced via this method demonstrated the utility of this fabrication approach. This unique, simple, and scalable method for fabrication of enclosed microfluidic devices not only ensures protection of devices from contamination and prevention of fluid evaporation, but also offers a method for commercial fabrication of porous-media analytical devices.

Solomon technique of fetoscopic laser ablation is associated with improved perinatal outcomes

Fetoscopic laser ablation of pathogenic vascular connections between twin circulations is the mainstay of treatment for twin-twin transfusion syndrome (TTTS). Laser photocoagulation can be performed in either a selective manner or by utilizing the Solomon technique. The purpose of this study was to assess differences in perinatal and neonatal outcomes between fetuses undergoing either selective laser ablation or laser photocoagulation using the Solomon technique for treatment of TTTS.

Highly Conductive and Compliant Silver Nanowire Nanocomposites by Direct Spray Deposition

The silver nanowire (Ag NW)/elastomer nanocomposite represents a prototypical form of a compliant conductor for flexible and stretchable electronic devices. The widespread implementations are currently hindered by the complicated procedures to effectively disperse Ag NWs into elastomer matrices. In this study, we report a facile and scalable coating process to create Ag NW nanocomposites on various flexible/stretchable substrates. As-synthesized Ag NWs from the high-yield polyol-reduction approach are homogeneously dispersed into a variety of dilute elastomer solutions, thereby enabling direct spray deposition into highly compliant conductors. The as-prepared nanocomposite exhibits excellent conductivity (∼11,000 S/cm) and high deformability to 100% strain. The stable electrical properties are largely retained under repetitive mechanical manipulations including stretching, bending, and folding. The patterned features of conductive nanocomposites are conveniently accessed using shadow masks or selective laser ablation. The practical suitability is demonstrated by the successful implementations of a stretchable sensing patch and a flexible light-emitting diode display.

Current Treatments of Post-traumatic Stress Disorder and Amygdala Ablation as a Potential Cutting-Edge Therapy in Its Refractory Cases.

Post-traumatic stress disorder (PTSD)is a very common psychiatric disorder occurring in an individual of any age, gender, or racewho underwent trauma, with women being twice more at risk than men. It is generally seen more in American Indians, United States Latinos, and African American ethnic groups. A patient is diagnosed with PTSD if the symptoms of intrusion, avoidance, changes in cognition and emotions, arousal, and mood reactivity changes persist for more than a month and cause the individual severe difficulty in their everyday cognitive and psychological functioning. The psychological treatment includes numerous therapies including trauma-focused therapies such as cognitive behavioral therapy, cognitive processing therapy, prolonged exposure therapy, eye movement desensitization and reprocessing, and non-trauma-focused therapies such as relaxation techniques, interpersonal therapy, and mindfulness. Various pharmacological measures have also been tried with mixed results such as selective serotonin reuptake inhibitors, benzodiazepines, adrenergic drugs, atypical antipsychotics, and mood stabilizers like lithium and valproate. As numerous studies have proven, PTSD is linked with right-side stimulation of the amygdala. The purpose of this article is to highlight the use of extremely selective laser ablation of the amygdala-hippocampal unit as a successful surgical intervention for medically unresponsive PTSD and as a revolutionary solution and prospective cutting-edge therapy in the near future.

Preparation of liquid metal circuits on flexible polymers by selective laser ablation: Essential mechanism of non-conductivity in ablation part

This work prepared liquid metal films by roll coating on various flexible substrates and then selectively ablated unwanted areas using near-infrared or ultraviolet lasers. The ablated regions lost their conductivity, while the remaining areas remained highly conductive, resulting in the successful fabrication of high-precision liquid metal circuits on various flexible and stretchable substrates. Mechanism of non-conductivity of liquid metal after laser ablation was investigated in detail. First, under the action of laser, most of Galinstan is evaporated. Second, although very small amounts of liquid metal still remain, they exist in the isolated state and cannot form continuous conductive paths. Finally, a continuous porous network material appears in the residue after laser ablation, which is the non-conductive oxidation products of metallic gallium, indium, and tin. Due to the above three reasons, the liquid metal film after laser ablation can realize the transition from conductive to non-conductive, and the patterning of the liquid metal can be achieved. The application of liquid metal circuits prepared by this method in wearable sensors (electronic skin) was explored. This study contributes to the mechanism of selective laser ablation to fabricate liquid metal circuits, promoting a better understanding of this method in the field of flexible electronics.

Selective laser ablation preparation of Ag grid transparent electrodes with fractal-combined structures and optimization of fractal grid pitch

New fractal-structured patterns with different grid period combinations were designed and applied to Ag grid transparent electrodes (TEs). Based on the principle of decreasing or increasing Ag grid line densities in local areas, the optical transmittance or electrical conductivity of the resulting Ag grid TEs could be selectively enhanced, thus effectively improving its comprehensive performance. Fractal-combined Ag grid TEs with different combined periods were firstly prepared by selective laser ablation of sputtered Ag films, and compared with the corresponding regular periodic Ag grid TEs to determine the optimal combined periods. The results indicated that the combined periods of 4 and 9 enabled the Ag grid TE to have a relatively high figure of merit of 4.92 × 10–2 Ω−1. This optimal fractal-combined Ag grid TE was chosen to optimize grid pitch for further comprehensive performance improvement. Using a large grid pitch of 1.1 mm could achieve the best trade-off between optical transmittance and electrical conductivity, and produced the best comprehensive performance with the maximum figure of merit of 5.17 × 10–2 Ω−1. The fractal-combined structure provides a unique scheme for flexibly designing and preparing grid patterns in metal TEs.

Far‐Field Parallel Direct Writing of Sub‐Diffraction‐Limit Metallic Nanowires by Spatially Modulated Femtosecond Vector Beam

AbstractMetallic nanowires have exhibited paramount importance in achieving functional electrical, electrochemical, and optical performances due to their unique physicochemical properties. Efficient fabrication of the nanowires with controllable geometry and line width is highly required in related applications. Here a new far‐field laser parallel direct writing approach for fabricating nanowire array far beyond the diffraction limit by a modulated vector beam with dual‐peak intensity distribution is reported. Such a modulated beam can perform selective laser ablation to fabricate nanowires, whose line width can be largely reduced by tuning the dual‐peak orientation relative to the laser scanning direction. As a demonstration, a 157 nm‐wide (less than λ/3) gold nanowire, reaching ≈1/20 of the diffraction limit, has been fabricated in far field by using a low numerical aperture microscope objective (NA = 0.1). The nanowire fabrication efficiency is also largely improved by applying multifocal modulated vector beams for parallel processing.

Construction of Graphene-Based "In-Paper" 3D Interdigital Microelectrodes for High Performance Metal-Free Flexible Supercapacitors.

Flexible micro-supercapacitors (MSCs) are promising power sources of portable/wearable electronic devices. Electrodes are the key components determining performance of the MSCs, but it still remains a big challenge in either materials or fabrication methods to achieve both high charge storage capability and robust mechanical flexibility. Herein, a novel water-cooling assisted selective laser ablation (WASLA) technique is demonstrated for scale-fabrication of "embedded-in-paper" 3D graphene-cellulose composite interdigital electrodes (3D GCCIEs) in a mask-free and chemical-free manner. The obtained electrodes are endowed with 3D charge storage geometry, high electrical conduction, freely designed patterns, and the inherent advantages of paper substrate. Therefore, the 3D GCCIEs-based MSC exhibits excellent overall performance including large specific capacitances, high rate performance, impressive cyclic stability, and remarkable mechanical flexibility. Moreover, metal-free 3D GCCIE-MSC integrated arrays with diverse shapes composed of linear/curved interdigital electrodes are also fabricated, and a letter-shaped MSC array successfully lit a light emitting diode light in both flat and folded status demonstrating excellent device flexibility. The as-fabricated 3D GCCIE-MSCs have shown great application potential as power sources of flexible electronic devices, and the WASLA method proves to be an effective strategy for scale-manufacturing high performance paper-based charge storage devices not limited to supercapacitors.

Selective Passivation of Three-Dimensional Carbon Microelectrodes by Polydopamine Electrodeposition and Local Laser Ablation

In this article, a novel approach for selective passivation of three-dimensional pyrolytic carbon microelectrodes via a facile electrochemical polymerization of a non-conductive polymer (polydopamine, PDA) onto the surface of carbon electrodes, followed by a selective laser ablation is elaborated. The 3D carbon electrodes consisting of 284 micropillars on a circular 2D carbon base layer were fabricated by pyrolysis of lithographically patterned negative photoresist SU-8. As a second step, dopamine was electropolymerized onto the electrode by cyclic voltammetry (CV) to provide an insulating layer at its surface. The CV parameters, such as the scan rate and the number of cycles, were investigated and optimized to achieve a reliable and uniform non-conductive coating on the surface of the 3D pyrolytic carbon electrode. Finally, the polydopamine was selectively removed only from the tips of the pillars, by using localized laser ablation. The selectively passivated electrodes were characterized by scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy methods. Due to the surface being composed of highly biocompatible materials, such as pyrolytic carbon and polydopamine, these 3D electrodes are particularly suited for biological application, such as electrochemical monitoring of cells or retinal implants, where highly localized electrical stimulation of nerve cells is beneficial.

Feasibility analysis and process characteristics of selective laser ablation assisted milling Inconel 718

Feasibility analysis and process characteristics of selective laser ablation assisted milling Inconel 718

Laser direct patterning induced the tunable optical properties of indium tin oxide micro-hole arrays films

Here we introduce a facile method to fabricate patterned indium tin oxide (ITO) thin films via selective laser ablation at ambient conditions. By scanning the ITO thin films with focused Nd: YAG pulsed laser, the ITO thin films were selective ablated and patterned without using any conventional chemical etching or photolithography steps. Then we investigated the effects of scanning rate for the structure, morphology and optical properties of patterned ITO thin film. These results indicate that the epsilon-near-zero (ENZ) wavelength of ITO thin films can be tuned from 1100 nm to 1340 nm by adjusting the period of the micro-hole array in microstructure. The nonlinear absorption response of patterned ITO films was about 2.85 time than of the as-deposited ITO thin film. Additionally, the results of the Finite-Difference Time-Domain (FDTD) simulation are in good agreement with those of the experiments.

Wireless Humidity Sensor for Smart Packaging via One‐step Laser‐Induced Patterning and Nanoparticle Formation on Metallized Paper

AbstractIn this work, a scalable and rapid process is developed for creating a low‐cost humidity sensor for wireless monitoring of moisture levels within packaged goods. The sensor comprises a moisture‐sensitive interdigitated capacitor connected to a planar spiral coil, forming an LC circuit whose resonant frequency is a function of environmental humidity. The sensor is fabricated on a commercially available metallized parchment paper through selective laser ablation of the laminated aluminum (Al) film on the parchment paper substrate. The laser ablation process provides a unique one‐step patterning of the conductive Al layer on the paper while simultaneously creating high surface area Al2O3nanoparticles within the laser‐ablated regions. The intrinsic humidity‐responsive characteristics of the laser‐induced Al2O3nanostructures provide the wireless sensor with a tenfold higher sensitivity to humidity than a similar LC resonant sensor prepared by conventional photolithography‐based processes on FR‐4 substrates. The frequency change of the sensor is observed to be a linear function within the range of 0−85% RH, providing an average sensitivity of −87 kHz RH−1with good repeatability and stable performance. Furthermore, the employment of scalable laser fabrication processes using commercially available inexpensive materials renders these technologies viable for roll‐to‐roll manufacturing of low‐cost wireless sensors for smart packaging applications.

Fabrication and performance improvement of Ag grid transparent conducting films using selective laser ablation

Fabrication and performance improvement of Ag grid transparent conducting films using selective laser ablation

Superior Verbal Memory Outcome After Stereotactic Laser Amygdalohippocampotomy.

Objective: To evaluate declarative memory outcomes in medically refractory epilepsy patients who underwent either a highly selective laser ablation of the amygdalohippocampal complex or a conventional open temporal lobe resection.Methods: Post-operative change scores were examined for verbal memory outcome in epilepsy patients who underwent stereotactic laser amygdalohippocampotomy (SLAH: n = 40) or open resection procedures (n = 40) using both reliable change index (RCI) scores and a 1-SD change metric.Results: Using RCI scores, patients undergoing open resection (12/40, 30.0%) were more likely to decline on verbal memory than those undergoing SLAH (2/40 [5.0%], p = 0.0064, Fisher's exact test). Patients with language dominant procedures were much more likely to experience a significant verbal memory decline following open resection (9/19 [47.4%]) compared to laser ablation (2/19 [10.5%], p = 0.0293, Fisher's exact test). 1 SD verbal memory decline frequently occurred in the open resection sample of language dominant temporal lobe patients with mesial temporal sclerosis (8/10 [80.0%]), although it rarely occurred in such patients after SLAH (2/14, 14.3%) (p = 0.0027, Fisher's exact test). Memory improvement occurred significantly more frequently following SLAH than after open resection.Interpretation: These findings suggest that while verbal memory function can decline after laser ablation of the amygdalohippocampal complex, it is better preserved when compared to open temporal lobe resection. Our findings also highlight that the dominant hippocampus is not uniquely responsible for verbal memory. While this is at odds with our simple and common heuristic of the hippocampus in memory, it supports the findings of non-human primate studies showing that memory depends on broader medial and lateral TL regions.

Effects of static and dynamic femtosecond laser modifications of Ti/Zr multilayer thin films

The experimental study of the static and dynamic femtosecond laser ablation of the multilayer 15x(Ti/Zr)/Si system is reported. The layer-by-layer selective laser ablation mechanism was studied by analysis of the surface morphology and elemental composition in static single pulse irradiation in a range of pulse energy from 10 to 17 upmu J. The selective ablations, as number of concentric circles in modified spots are increased with the pulse energy. The boundary between the circles was shown a change in the depth, comparable to the thickness of the individual layers. Changes in the elemental composition at the edges are associated with the removal of the layer by layer. The dynamic multipulse irradiation was observed via the production of lines with laser-induced periodic surface structures (LIPSS) at different laser parameters (scan velocities and laser polarization). The spatial periodicity of the formed LIPSS depends on changes in the effective number of pulses and laser polarization, as well as the nature of the material. For better interpretation of the experimental results, simulations have been conducted to explore the thermal response of the multiple layered structure 15x(Ti/Zr) after static single pulse irradiation.Graphic

Clinical Outcomes of Laser Asymmetric Keratectomy to Manage Postoperative Adverse Effects–A Retrospective Clinical Trial

Background: Laser asymmetric keratectomy reduces the regional asymmetry of corneal thickness. Objective: We aimed to describe the clinical outcomes of laser asymmetric keratectomy keratectomy with laser refractive surgery performed to resolve the adverse effects following ophthalmic surgeries. Methods: We compared the preoperative and postoperative outcomes and complaints of blurring after performing laser asymmetric keratectomy with laser refractive surgery in 24 eyes of 16 patients with a deviation sum in corneal thickness in four directions >80 µm. Laser asymmetric keratectomy with laser refractive surgery, with full integration of the Vision Up software, was used to analyze the corneal thickness deviation, employed selective laser ablation to create central symmetry on the thicker cornea to reduce regional asymmetry of corneal thickness, simultaneously correcting the refractive power and myopic shift. The pre-and postoperative clinical and topographic findings were analyzed. Results: The patients’ age was 37.57±22.30 (range, 23–65) years. The follow-up period was 16.56±3.23 months. The spherical equivalent (p=0.026), sphere (p=0.022), uncorrected distance visual acuity (LogMAR, p=0.045), blurring score (p=0.000), central corneal thickness (p=0.024), sum of deviations in corneal thickness in four directions (p=0.02), distance between the maximum posterior elevation and visual axis (p=0.04), and kappa angle (p=0.031), significantly decreased postoperatively. The efficiency and safety indices were 0.96±0.11 and 1.00, respectively. There was no myopic regression or blurred vision postoperatively. Conclusion: Performing laser asymmetric keratectomy with laser refractive surgery improved corneal symmetry and visual acuity and reduced blurring.