Local Laser Ablation Research Articles

Non-surgical treatment of hidradenitis suppurativa: the role of cryotherapy.

Hidradenitis suppurativa is a chronic and recurrent inflammatory disease with a great impact on a patient's quality of life, due to the painful involvement of very sensitive areas, such as the groin, mammary area, and genitals, with malodourous discharge. Multiple treatment options are available; however, no single treatment is effective for all patients, and usually, a combination of medical therapy with various surgical and physical procedures is provided. Cryotherapy is not a routine technique to treat HS, although usually available in the majority of medical clinics, and is cheaper than laser and surgical treatments. The aim of this study was to evaluate the effectiveness of cryotherapy on persistent HS nodules, to reduce the burden of local disease. Retrospective observational study in all patients treated with liquid nitrogen cryotherapy for persistent nodules of hidradenitis suppurativa in the last 2 years, with at least 6 months of follow-up after the procedure. Disease severity was assessed with Hurley staging and sonographic staging according to SOS-HS (18 MHz probe, Esaote-MyLab™). The results were scored with a 0-3 points scale, as complete remission (3), partial response (2 to 1), or no response (0), after one session of treatment. Local cleansing and antiseptic treatment after the procedure was the same as previously performed in each patient, not to influence recovery. In total, 23 patients were included, with a total of 71 persistent nodules treated with a single cryotherapy session. The treatment has been effective in 63 out of 71 nodules treated (88.7%), and the patients attested that they recommend the treatment, the discomfort during recovery was minimal, and the management was not different from daily routine. Persistence was considered as having a failure rate (11.3% overall) and occurred in 7.5% of the nodules of the axillary region, 18.2% on the groin, and 11.2% for nodules of the gluteal region. Cryotherapy is a simple and effective procedure for the treatment of persistent nodules of HS not responding to medical therapy, and it is a valid alternative to local surgery or laser ablation.

Substrate-Induced Dissipative and Non-Linear Effects in RF Switches: Probing Ultimate Performance Based on Laser-Machined Membrane Suspension

With the evolution of radio frequency (RF)/microwave technology, there is a demand for circuits that are able to meet highly challenging RF front end specifications. Silicon-on-insulator (SOI) technology is one of the leading platforms for upcoming wireless generation. The degradation of performance due to substrate coupling is a key problem to address for telecommunication circuits, especially for the high throw count switches in RF front ends. In this context, a fast, flexible and local laser ablation technique of the silicon handler allows for the membrane suspension of large millimeter-scale circuits. This approach enables the evaluation of the ultimate performance in the absence of the substrate, i.e., without dissipative losses and substrate-induced non-linear effects, on capacitive comb coupling structures and RF switches. Compared to high-resistivity SOI substrates, the high frequency characterization of RF membrane switches reveals a superior linearity performance with a reduction in second and third harmonics by 17.7 dB and 7.8 dB, respectively. S-parameter analysis also reveals that membrane suspension entails insertion losses that are improved by 0.38 dB and signal reflection lowered by 4 dB due to a reduced off-state capacitance. With reference to a trap-rich substrate, the membrane suspension also achieves an additional 7.8 dB reduction in the second harmonic, indicating that there is still scope for improvement in this figure of merit. The obtained results demonstrate a new way to evaluate optimized circuit performance using post-fabrication substrate engineering.

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.

Improving the conductivity of graphite-based films by rapid laser annealing.

We present a method to anneal devices based on graphite films on paper and polycarbonate substrates. The devices are created using four different methods: spray-on films, graphite pencil-drawn films, liquid-phase exfoliated graphite films, and graphite powder abrasion-applied films. We characterize the optical properties of the films before and after laser annealing and report the two-terminal resistance of the devices for increased laser power density. We find the greatest improvement (16× reduction) in the resistance of spray-on film devices starting from 25.0 kΩ and reaching 1.6 kΩ at the highest annealing power densities. These improvements are attributed to local laser ablation of binders, stabilizers, and solvent residues left in the film after fabrication. This work highlights the utility of focused laser annealing for spray-on, drawn, printed, and abrasion fabricated films on substrates sensitive to heat/thermal treatments.

Slow speed friction behaviour of a-C:H with different fs-laser micro-patterns against diamond tip in hyaluronic acid

Slow speed and different normal forces were chosen for investigation of the friction under short impact sliding. The base material is a hydrogenated diamond-like carbon coating (a-C:H). The coating was modified by femtosecond laser micro-patterning (µ-patterning). Three different µ-patterns were generated in the hydrogenated diamond-like carbon (DLC) coating and compared with a-C:H in the “as-deposited” condition. The sliding behaviour was demonstrated without an intermediate medium and with fluid addition. In the latter case, hyaluronic acid gel (HYA) was added. Gentle or deep dimpling by local femtosecond laser ablation resulted in a significantly more variable coefficient of friction (COF) curvature. During dry sliding of the diamond tip against the laser µ-patterned a-C:H, a zig-zag shape of the COF curve was observed. For deep laser µ-patterned DLC under high normal force of 10 N, sudden switches to very low COF down to 0.02 occurred when HYA was added. For hydrogenated DLC with gentle laser µ-patterning, the lowest COF were observed in this study under hyaluronic gel lubrication and low normal forces of 1 N. A volume expansion of the DLC and negative coefficients of friction were observed after loading with 1 N for some coating variants. For laser-induced periodic surface structured (LIPSS) DLC, at low loads of 1 N the COF became higher while at high normal forces like 10 N, a positive trend of LIPSS on the friction behaviour were seen under hyaluronic gel addition. Laser µ-patterning effected graphitization of small or large regions of the a-C:H coating. The defect-rich graphite sections on laser µ-patterned DLCs influenced the crystallisation behaviour of HYA and its distribution.

Current approaches to cleft lip revision

Cleft lip repair requires multidisciplinary follow-up throughout a child's life and often requires lip revision surgery in adolescence to restore function and symmetry of the lip. There is significant variability in the approaches taken for lip repair and therefore a review of current techniques and subsequent guidance to secondary cleft lip repair is warranted. New methods of secondary reconstruction can be divided into superficial or muscle related. Recent suggestions for superficial reconstruction include botulinum toxin injection, silicone gel sheeting, local flap reconstruction, fat grafting, and CO2 laser ablation. Suggestions for muscular reconstruction include pedicled prolabial flaps, modified Abbe flap, and orbicularis oris eversion. Secondary cleft lip deformities can be classified as superficial or muscle related. Superficial problems require relatively minor treatments such as laser, local scar revisions, small local flaps, mucosal excision, or fat grafting. Muscle deformities generally require total lip revision and rerepair as a first step to achieving longstanding improvements in lip esthetics and function. Cleft lip revision should only be considered in concert with the patient, be based on the patient's concerns and desires, and offered at the appropriate timeline to improve social integration and/or psychosocial wellbeing.

21% efficient screen-printed n-type silicon wafer solar cells with implanted phosphorus front surface field

In this paper n-type PERT (Passivated Emitter and Rear Totally diffused) silicon wafer solar cells with a diffused boron rear emitter and an implanted phosphorus front surface field are investigated. A key feature of the n-PERT rear emitter cell is that it uses the same sequence of surface passivation, rear local laser ablation and screen-printing processes as a commercial p-type PERC (Passivated Emitter and Rear Contact) cell. Therefore, this cell structure is very industrially relevant as it could simplify a production line upgrade from p-type cells to n-type cells. Additionally, ion implantation provides an elegant single-side doping process that further simplifies the processing sequence of n-PERT cells. Ion implantation also provides excellent control over the doping profile via a variation of post-implant annealing time. The effect of annealing time on the implanted phosphorus surface was evaluated in this study in terms of the front surface field dopant profile and its impact on the solar cells’ electrical characteristics. A shallower front surface doping profile resulted in better short wavelength response. Additionally, the performance of two different Al pastes (with and without Si content in the paste) was compared. The better-performing Al-Si paste generates a homogeneous Al-p+ region under the contacts, which reduces the recombination at the contacts. By tailoring the phosphorus front surface field profiles and by minimising the recombination during the rear Al contact formation, efficiencies of up to 21% on large area 244 cm2n-type wafers were achieved so far.

Actin Disassembly: How to Contract without Motors?

Contractile actin networks take on various functions in cells. How disordered actin networks contract is still poorly understood. A recent study proposes a contractile mechanism that is driven by actin disassembly and required to prevent chromosome losses in starfish oocytes.

Interface oxides in femtosecond laser structured plated Ni-Cu-Ag contacts for silicon solar cells

Light-induced plating of a Ni-Cu-Ag stack allows for high efficient and potentially low cost solar cell metallization. The definition of the contact structure is performed by local laser ablation of the solar cells surface passivation layer. By using a femtosecond pulsed UV laser the crystal damage due to ablation is minimized in respect to any other approach of laser-structuring. Within the study presented plated contacts on femtosecond structured silicon are evaluated regarding electrical and mechanical properties. The results show that contact resistance is determined by a highly inhomogeneous interface oxide layer that is formed while femtosecond pulsed laser ablation on textured solar cell surfaces. Silicidation of the silicon/nickel contact interface is assumed to be essential for adhesion and low contact resistances. However, the results presented indicate that mechanical adhesion of contacts plated on femtosecond laser structured surfaces is ensured by the laser-induced microstructure and that low contact resistance and high fill-factors are reached when interface oxides are fully dissolved. Therefore, controlling the surface properties before metal-deposition is essential for plated contacts on femtosecond pulse laser structured silicon while silicide formation may be superfluous.

Mechanistic study on black and grey spot growth in OLEDs performed on laser-ablated pinholes in the cathode

Local laser ablation of the cathode of OLEDs has been applied to create a population of pinholes of the same size. This enables the direct comparison at different conditions of black spots and grey spots in the emission of OLEDs as a result of water ingress into the device. We confirmed earlier observations on the operational effect of black spot growth as determined in a sequential test on particle induced pinholes. Furthermore, we measured the operational effect in parallel, providing data that are test independent. With the same population of pinholes we studied the operational effect of grey spot growth. The observed larger operational effect of grey spot growth with respect to that of black spot growth is attributed to a lateral flow of protons to the centre of the black spot. In this part of the black spot a depletion region is present which is created by transport of H3O+ to the cathode under the influence of the applied electric field. This proposal is supported by the observation of black and grey spot growth in polymer LEDs on basis of PEDOT:PSS with increased pH.

Management of Vaginal Intraepithelial Neoplasia

Vaginal intraepithelial neoplasia (VaIN) accounts for 0.4% of the lower genital tract intraepithelial disease. Various treatments have been reported often as small case series or reports. An electronic search of the Ovid MEDLINE (from 1948 to present) and PubMed was performed, and only articles written in English were reviewed. All articles ranging from case reports to randomized controlled trials were included. This review critically appraises the published evidence for different treatment modalities and gives an overview of these options. The 3 main modalities reported were surgery, brachytherapy, and medical management. Surgery included local excision, laser ablation, vaginectomy, and cavitational ultrasonic ablation. Medical management included topical 5% imiquimod, 5-fluorouracil, and tricholoroacetic acid. All treatments had good success rates for disease clearance with low rates of progression to cancer. Prerequisites for ablative treatments are the lesion is fully visible and adequately examined by biopsy to exclude invasion. Where invasion is suspected or cannot be excluded (e.g., at the vault suture line), surgical excision is essential. Brachytherapy and vaginectomy, although effective, have a limited place because of their related morbidity. Treatment choice may depend on the availability of equipment and expertise. Conservative options in the form of laser ablation and topical agents are useful as first-line treatment methods especially in young women and for multifocal disease. Radical options like brachytherapy and vaginectomy should be reserved for highly selected cases. Evidence from a randomized controlled trial of first-line treatment with surgical and medical therapies is needed to compare treatment success and impact on quality of life.

Towards 20% efficient large‐area screen‐printed rear‐passivated silicon solar cells

ABSTRACTWe have implemented a baseline solar cell process based on today's standard industrially manufactured silicon solar cells. Using this process, we achieve conversion efficiencies up to 18.5% applying 125 × 125 mm² pseudo‐square p‐type 2–3 Ω cm boron‐doped Czochralski silicon wafers featuring screen‐printed front and rear contacts and a homogenously doped 70 Ω/□ n+‐emitter. Optimizing a print‐on‐print process for the silver front side metallization, we reduce the finger width from 110 to 70 µm, which increases the conversion efficiency up to 18.9% due to the reduced shadowing loss. In order to further increase the efficiency, we implement two different dielectric rear surface passivation stacks: (i) a silicon dioxide/silicon nitride stack and (ii) an aluminium oxide/silicon nitride stack. The rear contacts to the silicon base are formed by local laser ablation of the passivation stack and aluminium screen printing. The dielectric layer stacks at the rear decrease the surface recombination velocity from Seff,rear = 350 cm/s for a full‐area Al back surface field down to Seff,rear = 70 cm/s and increase the internal reflectance from 61% up to 91%. The improved solar cell rear increases the conversion efficiency η up to an independently confirmed value of 19.4%, the short‐circuit current density Jsc up to 38.9 mA/cm² and the open‐circuit voltage Voc up to 662 mV. The detailed solar cell analysis reveals potential to further increase the conversion efficiency towards 20% in the near future. Copyright © 2011 John Wiley & Sons, Ltd.

Contact Formation and Recombination at Screen-Printed Local Aluminum-Alloyed Silicon Solar Cell Base Contacts

We study recombination properties and the formation of base contacts, which are realized by local laser ablation of a dielectric stack and the subsequent full-area screen printing of an Al paste. Based on charge-carrier lifetime measurements using the camera-based calibration-free dynamic infrared lifetime mapping technique, we determine contact reverse saturation current densities as low as J0, cont = 9 X102 fA/cm2 on 1.5-Ωcmp-type float-zone silicon (FZ-Si) and J0, cont = 2X104 fA/cm2 on 200- Ωcmp-type FZ-Si. Scanning electron microscopy images reveal that the thickness of the highly Al-doped (Al-p+) layer considerably depends on the contact size and the contact layout (e.g., point or line contacts). Based on this finding, we show that Al-p+ layer thickness WAl-p+ significantly affects the contact recombination. As a result, we show which local contact geometry is most appropriate for the lowest contact recombination employing local Al-alloyed contacts.

Micro-structuring of CIGS thin-film coated on Mo back contact by ultrafast laser ‘rail-roading’ patterning

We report selective patterning process, laser 'rail-roading' scribing method, of which operating principle is based on transient force balance between the material properties including cohesion and adhesion forces subjected to underlying substrate and laser-induced shock compression and shear forces. By using dual fs-laser beam lines with an interval larger than laser spot size, we provide a proof of the concept by patterning the photovoltaic modules based on CIGS (Cu(In,Ga)Se2) coated on Mo electrode. With varying the interval between the two laser beam tracks, we can provide intact Mo back contact surface without any residues in a manner of more facile, high-speed and high scribing efficiency. We have interpreted the effect of the ambient gases and grooving width on the scribing performance in terms of the cohesion forces between the grains of CIGS thin films as well as adhesion force between underlying Mo layer and CIGS, which are mainly governed by local laser ablation and peening process followed by laser-induced shock compression, respectively.

Induction of Th1Immune responses following laser ablation in a murine model of colorectal liver metastases

BackgroundPreliminary experimental studies have suggested that the in situ destruction of tumor tissue by local laser ablation (LA) may also stimulate host immunity against cancer. We investigated local and systemic induction of immune responses after laser ablation in the setting of residual tumor.MethodsA murine colorectal cancer (CRC) liver metastasis model was used. Selected tumors of liver CRC bearing mice and livers of mice without tumor induction were treated with LA. Liver and tumor tissues from the ablation sites and from distant sites were collected at various time points following LA and changes in CD3+ T cells and Kupffer cells (F4/80 marker) infiltration and the expression of interferon gamma (IFNγ) were investigated by immunohistochemistry and ELISpot. Base line levels of CD3+ T cells and Kupffer cells were established in untreated mice.ResultsThe presence of tumor induced significant accumulation of CD3+ T cells and Kupffer cells at the tumor-host interface, within the tumor vascular lakes and increased their baseline concentration within the liver parenchyma. LA of the liver induced accumulation of CD3+ T-cells and Kupffer cells at the site of injury and systemic induction of immune responses as discerned by the presence of IFNγ secreting splenocytes. LA of liver tumors induced significant increase of CD3+ T-cells at site of injury, within normal liver parenchyma, and the tumor-host interface of both ablated and distant tumors. In contrast Kupffer cells only accumulated in ablated tumors and the liver parenchyma but not in distant tumors. IFNγ expression increased significantly in ablated tumors and showed an increasing trend in distant tumors.ConclusionLaser ablation in addition to local tumor destruction induces local and systemic Th1 type immune responses which may play a significant role in inhibiting tumor recurrence from residual micrometastases or circulating tumor cells.

Recombination at local aluminum-alloyed silicon solar cell base contacts by dynamic infrared lifetime mapping

The application of local aluminum (Al)-alloyed contacts to the p-type base of silicon solar cells reduces minority charge carrier recombination due to the formation of a local back surface field (LBSF). We study the recombination properties and formation of base contacts, which are realized by local laser ablation of a dielectric stack (laser contact opening - LCO) and subsequent full area screen printing of Al paste. Based on charge carrier lifetime measurements using the camera-based and calibration-free dynamic infrared lifetime mapping (ILM) technique, we determine contact recombination velocities at the contacts as low as Scont = 65 cm/s on 200 Ωcm float-zone silicon (FZ-Si) and corresponding reverse saturation current densities of J0,cont = 900 fA/cm² on 1.5 Ωcm FZ-Si. As a result we show that local contact geometries with point contact radii r > 100 µm and line contact widths a > 80 µm are appropriate for lowest contact recombination employing local Al alloyed contacts. Furthermore, complete and high quality laser ablation of the dielectric stack is necessary for the formation of a sufficiently thick LBSF. © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of SiliconPV 2011. local back surface field; carrier lifetime; laser ablation; silicon solar cells

Therapy for Unresectable Recurrent and In-Transit Extremity Melanoma

Unresectable recurrent and in-transit extremity melanoma presents a dilemma for the treating physician. While the disease is confined to the involved limb, the survival mimics that of multiple nodal metastases, with a 10-year survival rate of approximately 40%. This represents late-stage disease for which curative treatment options are limited. To review the current treatment strategies for stage IIIB (N2c) in-transit and recurrent melanoma focusing on the options for unresectable disease, MEDLINE was searched for studies of known and experimental treatments for in-transit and recurrent extremity melanoma. Further results were obtained after review of the initial citations. For unresectable recurrences and in-transit metastases, therapies are limited to palliative (radiation), local (intratumoral injection, laser ablation and electroporation), regional (isolated limb perfusion/infusion), and systemic (chemotherapy) when local or regional techniques are not feasible. In this patient population, intratumoral techniques have a limited role with current treatment regimens, but with the development of new drugs, these techniques may have more utility. If not contraindicated, regional techniques provide the greatest control and have minimal operative morbidity. Until new regimens are available, systemic therapy continues to be associated with considerable toxicity and only marginal response rates.

Fabrication of a cell array on ultrathin hydrophilic polymer gels utilising electron beam irradiation and UV excimer laser ablation

Most of the surface patterning methods currently applied are based on lithography techniques and microfabrication onto silicon or glass substrates. Here we report a novel method to prepare patterned surfaces on polystyrene substrates by grafting ultrathin cell-repellent polymer layers utilising both electron beam (EB) polymerisation and local laser ablation techniques for microfabrication. Polyacrylamide was grafted onto tissue culture polystyrene (TCPS) dishes using EB irradiation. Water contact angles for these PAAm-grafted TCPS surfaces were less than 10° ( cos θ = 0.99 ) with PAAm grafted amounts of 1.6 μg/cm 2 as determined by ATR/FT-IR. UV excimer laser (ArF: 193 nm) ablation resulted in the successful fabrication of micropatterned surfaces composed of hydrophilic PAAm and hydrophobic basal polystyrene layers. Bovine carotid artery endothelial cells adhered only to the ablated domains after pretreatment of the patterned surfaces with 15 μg/mL fibronectin at 37 °C. The ablated domain sizes significantly influenced the number of cells occupying each domain. Cell patterning functionality of the patterned surfaces was maintained for more than 2 months without loss of pattern fidelity, indicating that more durable cell arrays can be obtained compared to those prepared by self-assembled monolayers of alkanethiols, as described in previous reports. The surface fabrication techniques presented here can be utilised for the preparation of cell-based biosensors as well as tissue engineering constructs.

Fast selective metal deposition on polymers by using IR and excimer VUV photons

The major advantages of infra-red (IR) lamp induced decomposition of metal organic films for large-area deposition of metal films on substrate surfaces, local excimer laser ablation of thin metal films, and subsequent electroless metal plating were combined to develop a novel fast selective metallisation technique for thermally stable polymers. With the new method, metal structures with high edge quality on different types of polyimide (PI) foils can be produced easily. Without damaging the underlying PI substrate, the metal organic film (e.g. palladium acetate, PdAc) can be decomposed by infra-red irradiation in only about one second. The precise etching capability of ArF excimer laser ablation at λ=193nm allows the IR-induced palladium (Pd) layers to be removed from the PI surface with one excimer laser pulse, selectively. The residual patterned Pd film on the PI surface then acts as an excellent catalyst for conventional electroless copper plating.

Cancer of the anus.

Cancers of the anus, whether keratinizing squamous, nonkeratinizing, clear-cell, or melanoma, are infrequent neoplasms. Small keratinizing (<4 cm2) with no deep invasion can be controlled by local excision or laser ablation, but larger ones may be treated by chemoirradiation, restricting abdominoperineal resection to recurrences. Neither melanomas nor clear-cell cancers are curable, and local control is the surgical objective. Prophylactic groin dissection is not required but, for enlarged nodes or in the presence of a positive sentinel node biopsy, may be curative in many cases and palliative in all.