Laser Scribing Process Research Articles

Electrodeposition on laser induced graphene dual conductive substrate as a free-standing electrode for asymmetric supercapacitors

Herein, combing laser-induced graphene (LIG) obtained by laser scribing on polyethersulfone (PES) films with carbon cloth (CC) forming novel dual conductive networks can cause the well-designed electrode materials possessing strong electric conductivity in favor of electron transferring. The free-standing NiCo/L-CC@PES-IG or Fe/L-CC@PES-IG have been prepared through laser scribing and electrodeposition processes at mild conditions. Fe/L-CC@PES-IG exhibits a high areal specific capacitance of 1544 mF cm−2 at a current density of 1 mA cm−2, which matches well with NiCo/L-CC@PES-IG (1840 mF cm−2). It is worth mentioning that the capacitance retention of NiCo/L-CC@PES-IG can reach 80 % at 10 mA cm−2, ca. 16 times that of NiCo/L-CC-IG (only 5 %) just adding small amount PES, which indicate that the dual conductive network synergistic effect of the external conductive graphene and the internal CC. The asymmetric supercapacitor (ASC) device is constructed using NiCo/L-CC@PES-IG as a positive electrode and Fe/L-CC@PES-IG as a negative electrode, which delivers a high areal energy density of 381 μWh cm−2 at the areal power density of 825.8 μW cm−2. This work provides a unique insight into the design of hybrid supercapacitor assembled with matching positive and negative electrodes, which will achieve the desired superhigh performance.

Picosecond pulsed laser scribing of Cd2SnO4-based CdTe thin-film solar cells on flexible glass

CdTe photovoltaic modules are the most commercially successful thin-film solar cells. In particular, flexible CdTe modules are a promising development in photovoltaic architecture. Cd2SnO4 (CTO) is a low-cost transparent conductive material with excellent optical and electrical properties. Although laser scribing is commonly used to produce cell interconnects in the manufacturing of thin-film PV modules, the laser scribing process window for CTO-based CdTe cells is narrow, and more research is needed on direct laser scribing of flexible CdTe solar cells. In this study, the picosecond pulsed laser scribing of CdTe solar cells with CTO front electrodes and flexible glass substrates was investigated using lasers with the wavelengths of 355 and 532 nm. The flexible cells were suctioned onto a working platform, and a direct ablation method was adopted. The damage and removal thresholds of the CTO, CdTe, and Ni layers were studied and the effects of the spot spacing, multilayer conditions, and laser polarization state were investigated. A method for determining the scribing parameters was proposed. Very smooth scribing grooves were obtained using the optimized laser scribing process. The series and shunt resistances of the cells after laser scribing showed no significant differences compared to those of the control cells.

Exploring charge regeneration effect in interdigitated array electrodes-based TENGs for a more than 100-fold enhanced power density

The vast potential of harnessing high entropy and abundantly available mechanical energy through triboelectric nanogenerators (TENGs) has attracted significant attention in recent years. However, the cost of harvesting this energy has often outweighed the energy collected. Recent advancements in TENGs for blue energy harvesting from water flow have shown great promise. In this study, we present a novel approach to optimize the performance of interdigitated electrode array-based TENGs operating in free-standing mode (IDA-FTENG) by introducing a gap-to-width ratio (GWR) relationship for the electrodes and its impact on the charge regeneration effects. We investigate the dependence of the charge regeneration effect on GWRs and the number of electrode pairs to enhance the performance of IDA-FTENGs, employing a rapid and industrially scalable laser scribing process for fabricating the devices. An optimized device, featuring a maximum of 34 interdigitated electrode grids, demonstrates a 140-fold increase in power density compared to conventional single electrode pair TENGs (SEP-TENGs). Furthermore, power density projections indicate that the optimized IDA-FTENGs can compete with current solar cells, if designed suitably. We showcase the applicability of the proposed IDA-FTENG devices in self-powered sensors, autonomous wireless operations, security monitoring, and smart home systems.

Size-dependent electrochemistry of laser-induced graphene electrodes

Laser-induced graphene (LIG) electrodes have become popular for electrochemical sensor fabrication due to their simplicity for batch production without the use of reagents. The high surface area and favorable electrocatalytic properties also enable the design of small electrochemical devices while retaining the desired electrochemical performance. In this work, we systematically investigated the effect of LIG working electrode size, from 0.8 mm to 4.0 mm diameter, on their electrochemical properties, since it has been widely assumed that the electrochemistry of LIG electrodes is independent of size above the microelectrode size regime. The background and faradaic current from cyclic voltammetry (CV) of an outer-sphere redox probe [Ru(NH3)6]3+ showed that smaller LIG electrodes had a higher electrode roughness factor and electroactive surface ratio than those of the larger electrodes. Moreover, CV of the surface-sensitive redox probes [Fe(CN)6]3– and dopamine revealed that smaller electrodes exhibited better electrocatalytic properties, with enhanced electron transfer kinetics. Scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy showed that the physical and chemical surface structure were different at the electrode center versus the edges, so the electrochemical properties of the smaller electrodes were improved by having rougher surface, more density of the graphitic edge planes, and more oxide-containing groups. The difference could be explained by the different photothermal reaction time from the laser scribing process that causes different stable carbon morphology to form on the polymer surface. Our results give a new insight on relationships between surface structure and electrochemistry of LIG electrodes and are useful for designing miniaturized electrochemical devices.

GaN Drift Layers on Sapphire and GaN Substrates for 1.2 kV Class Vertical Power Devices

The development of processes for epitaxial growth of vertical gallium nitride (GaN) drift layers enabling 1.2 kV breakdown voltage on low‐cost sapphire substrates is presented in comparison to GaN bulk substrates. The targeted blocking capability demands drift layers with a thickness of 10 μm and low but controllable n‐type doping. Using a growth rate of 2.5 μm h−1 the concentration of unintentionally incorporated carbon is sufficiently low to adjust the n‐type carrier concentration to ≈1 × 1016 cm−3 for all types of substrates. To assess GaN drift region properties in terms of forward bias conductivity and reverse bias blocking strength, a quasi‐vertical p‐n‐diode structure is utilized. Bow reduction of GaN‐on‐sapphire structures is achieved using a stealth laser scribing process. Breakdown voltages higher than 1600 V and a specific on‐state resistance as low as 0.7 mΩ cm2 are obtained with diodes fabricated on GaN substrates. Similar structures grown on sapphire show breakdown voltages of about 1300 V due to higher levels of current leakage. Comparing different types of substrates, a direct correlation between dislocation density in the drift layer with the leakage current in p‐n diodes is deduced.

Enhanced mitigation of cavitation erosion by means of femtosecond pulsed laser-induced hierarchical surface structures

Hierarchical structures were fabricated on brass surfaces by means of a straightforward 2-step laser-scribing process. We tested the ability of these surface structures to withstand cavitation erosion and compared their performance to untreated brass samples. We found that hierarchical surface structures reduced the eroded volume by a factor between 7.2 and 22.7 times when compared to untreated samples after 800,000 cavitation events. Additionally, the hierarchical surface structures reduced the erosion by a factor between 1.1 and 1.5 times when compared to samples patterned with only microchannel surface structures, for the same amount of cavitation events. Up to 800,000 laser-induced cavitation bubbles were generated at a fixed standoff distance of 0.5 to test the mitigation effect of the scribed surface structures on the eroded volume. The eroded volume was computed by means of confocal microscopy. The results show that additional roughness imposed by the hierarchical surface structure acts as an energy dissipator as observed by comparing the sizes of the higher order rebound cavitation bubbles. These findings provide a promising solution for protecting equipment from cavitation erosion.

Enhanced performance of solution‐processed carbon nanotube transparent electrodes in foldable perovskite solar cells through vertical separation of binders by using eco‐friendly parylene substrate

AbstractThe successful utilization of an eco‐friendly and biocompatible parylene‐C substrate for high‐performance solution‐processed double‐walled carbon nanotube (CNT) electrode‐based perovskite solar cells (PSCs) was demonstrated. Through the use of a novel inversion transfer technique, vertical separation of the binders from the CNTs was induced, rendering a stronger p‐doping effect and thereby a higher conductivity of the CNTs. The resulting foldable devices exhibited a power conversion efficiency of 18.11%, which is the highest reported among CNT transparent electrode‐based PSCs to date, and withstood more than 10,000 folding cycles at a radius of 0.5 mm, demonstrating unprecedented mechanical stability. Furthermore, solar modules were fabricated using entirely laser scribing processes to assess the potential of the solution‐processable nanocarbon electrode. Notably, this is the only one to be processed entirely by the laser scribing process and to be biocompatible as well as eco‐friendly among the previously reported nonindium tin oxide‐based perovskite solar modules.

A Rapid, Scalable Laser-Scribing Process to Prepare Si/Graphene Composites for Lithium-Ion Batteries.

Silicon has gained significant attention as a lithium-ion battery anode material due to its high theoretical capacity compared to conventional graphite. Unfortunately, silicon anodes suffer from poor cycling performance caused by their extreme volume change during lithiation and de-lithiation. Compositing silicon particles with 2D carbon materials, such as graphene, can help mitigate this problem. However, an unaddressed challenge remains: a simple, inexpensive synthesis of Si/graphene composites. Here, a one-step laser-scribing method is proposed as a straightforward, rapid (≈3min), scalable, and less-energy-consuming (≈5W for a few minutes under air) process to prepare Si/laser-scribed graphene (LSG) composites. In this research, two types of Si particles, Si nanoparticles (SiNPs) and Si microparticles (SiMPs), are used. The rate performance is improved after laser scribing: SiNP/LSG retains 827.6mAhg-1 at 2.0AgSi+C -1, while SiNP/GO (before laser scribing) retains only 463.8mAhg-1. This can be attributed to the fast ion transport within the well-exfoliated 3D graphene network formed by laser scribing. The cyclability is also improved: SiNP/LSG retains 88.3% capacity after 100 cycles at 2.0AgSi+C -1, while SiNP/GO retains only 57.0%. The same trend is found for SiMPs: the SiMP/LSG shows better rate and cycling performance than SiMP/GO composites.

Laser-induced graphene-based digital microfluidics (gDMF): a versatile platform with sub-one-dollar cost.

Digital microfluidics (DMF), is an emerging liquid-handling technology, that shows promising potential in various biological and biomedical applications. However, the fabrication of conventional DMF chips is usually complicated, time-consuming, and costly, which seriously limits their widespread applications, especially in the field of point-of-care testing (POCT). Although the paper- or film-based DMF devices can offer an inexpensive and convenient alternative, they still suffer from the planar addressing structure, and thus, limited electrode quantity. To address the above issues, we herein describe the development of a laser-induced graphene (LIG) based digital microfluidics chip (gDMF). It can be easily made (within 10 min, under ambient conditions, without the need of costly materials or cleanroom-based techniques) by a computer-controlled laser scribing process. Moreover, both the planar addressing DMF (pgDMF) and vertical addressing DMF (vgDMF) can be readily achieved, with the latter offering the potential of a higher electrode density. Also, both of them have an impressively low cost of below $1 ($0.85 for pgDMF, $0.59 for vgDMF). Experiments also show that both pgDMF and vgDMF have a comparable performance to conventional DMF devices, with a colorimetric assay performed on vgDMF as proof-of-concept to demonstrate their applicability. Given the simple fabrication, low cost, full function, and the ease of modifying the electrode pattern for various applications, it is reasonably expect that the proposed gDMF may offer an alternative choice as a versatile platform for POCT.

A Systematic Study on the Processing Strategy in Femtosecond Laser Scribing via a Two-Temperature Model.

Balancing quality and productivity, especially deciding on the optimal matching strategy for multiple process parameters, is challenging in ultrashort laser processing. In this paper, an economical and new processing strategy was studied based on the laser scribing case. To reveal the temperature evolution under the combination of multiple process parameters in the laser scribing process, a two-temperature model involving a moving laser source was developed. The results indicated that the peak thermal equilibrium temperature between the electron and lattice increased with the increase in the laser fluence, and the temperature evolution at the initial position, influenced by subsequent pulses, was strongly associated with the overlap ratio. The thermal ablation effect was strongly enhanced with the increase in laser fluence. The groove morphology was controllable by selecting the overlap ratio at the same laser fluence. The removal volume per joule (i.e., energy utilization efficiency) and the removal volume per second (i.e., ablation efficiency) were introduced to analyze the ablation characteristics influenced by multiple process parameters. The law derived from statistical analysis is as follows; at the same laser fluence with the same overlap ratio, the energy utilization efficiency is insensitive to changes in the repetition rate, and the ablation efficiency increases as the repetition rate increases. As a result, a decision-making strategy for balancing quality and productivity was created.

Effect of Ambient Environment on Laser Reduction of Graphene Oxide for Applications in Electrochemical Sensing.

Electrochemical sensors play an important role in a variety of applications. With the potential for enhanced performance, much of the focus has been on developing nanomaterials, in particular graphene, for such sensors. Recent work has looked towards laser scribing technology for the reduction of graphene oxide as an easy and cost-effective option for sensor fabrication. This work looks to develop this approach by assessing the quality of sensors produced with the effect of different ambient atmospheres during the laser scribing process. The graphene oxide was reduced using a laser writing system in a range of atmospheres and sensors characterised with Raman spectroscopy, XPS and cyclic voltammetry. Although providing a slightly higher defect density, sensors fabricated under argon and nitrogen atmospheres exhibited the highest average electron transfer rates of approximately 2 × 10-3 cms-1. Issues of sensor reproducibility using this approach are discussed.

Fabrication of flexible planar micro-supercapacitors using laser scribed graphene electrodes incorporated with MXene

The surge in demand for personalized electronic products has fueled the emergence and development of flexible electronic technology, giving rise to flexible energy storage devices. An integral component in these devices is planar micro-supercapacitors (MSCs), which hold immense promise for compatibility with flexible electronic products, especially in terms of their miniaturization, flexibility, integration, and customization. In this study, a fast, efficient, and environmentally friendly laser scribing technique has been employed to pattern MXene and graphene oxide (MXene/GO) composite films to prepare shape-controllable MXene and laser scribed graphene (MXene/LSG) patterned electrodes on a flexible substrate, which were then constructed into flexible MSCs. Based on the synergistic effect of these two-dimensional materials, MXene and LSG, the resulting adaptable devices exhibit exceptional electrochemical performance, including high areal capacitance, long cycle stability, superior flexibility, and mechanical stability. Furthermore, the use of a laser scribing process has pivotal implications for the scalable production of patterned electrodes and modular integration.

Laser Scribing Turns Plastic Waste into a Biosensor via the Restructuration of Nanocarbon Composites for Noninvasive Dopamine Detection.

The development of affordable and compact noninvasive point-of-care (POC) dopamine biosensors for the next generation is currently a major and challenging problem. In this context, a highly sensitive, selective, and low-cost sensing probe is developed by a simple one-step laser-scribing process of plastic waste. A flexible POC device is developed as a prototype and shows a highly specific response to dopamine in the real sample (urine) as low as 100 pmol/L in a broad linear range of 10-10-10-4 mol/L. The 3D topological feature, carrier kinetics, and surface chemistry are found to improve with the formation of high-density metal-embedded graphene-foam composite driven by laser irradiation on the plastic-waste surface. The development of various kinds of flexible and tunable biosensors by plastic waste is now possible thanks to the success of this simple, but effective, laser-scribing technique, which is capable of modifying the matrix's electronic and chemical composition.

Feather-like Gold Nanostructures Anchored onto 3D Mesoporous Laser-Scribed Graphene: A Highly Sensitive Platform for Enzymeless Glucose Electrochemical Detection in Neutral Media.

The authors present a novel sensing platform for a disposable electrochemical, non-enzymatic glucose sensor strip at physiological pH. The sensing material is based on dendritic gold nanostructures (AuNs) resembling feather branches, which are electrodeposited onto a laser-scribed 3D graphene electrode (LSGE). The LSGEs were fabricated via a one-step laser scribing process on a commercially available polyimide sheet. This study investigates several parameters that influence the morphology of the deposited Au nanostructures and the catalytic activity toward glucose electro-oxidation. The electrocatalytic activity of the AuNs-LSGE was evaluated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and amperometry and was compared to commercially available carbon electrodes prepared under the same electrodeposition conditions. The sensor demonstrated good stability and high selectivity of the amperometric response in the presence of interfering agents, such as ascorbic acid, when a Nafion membrane was applied over the electrode surface. The proposed sensing strategy offers a wide linear detection range, from 0.5 to 20 mM, which covers normal and elevated levels of glucose in the blood, with a detection limit of 0.21 mM. The AuNs-LSGE platform exhibits great potential for use as a disposable glucose sensor strip for point-of-care applications, including self-monitoring and food management. Its non-enzymatic features reduce dependence on enzymes, making it suitable for practical and cost-effective biosensing solutions.

Facile synthesis of MoS2 nanoflower-Ag NPs grown on lignin-derived graphene for Troponin I aptasensing

This article presents the development and application of a green lignin-derived graphene biosensor for Troponin I, a biomarker for Acute Myocardial Infarction (AMI). The graphene was synthesized from oil palm lignin through an optimized laser scribing process. While the three-dimensional nature of the laser-scribed lignin-derived graphene (3D LSG) is advantageous, it suffers from poor electrical conductivity due to the amorphous nature of lignin. Therefore, semi-conductive molybdenum disulphide (MoS2) precursor with conductive green silver nanoparticles (Ag NPs) was added to 0.5, 1.0, 1.5, and 2.0 g of 3D LSG to synthesize 3D LSG_MoS2_Ag NPs hybrids via an aqueous hydrothermal process. Morphological, physical, and structural analyses showed the presence of petal-like MoS2 nanoflower with Ag NPs on the 3D LSG surface. The strong interrelation between 3D LSG, MoS2, and Ag NPs was confirmed by X-ray spectroscopy, Raman spectroscopy and energy dispersive spectroscopy (EDS). Specifically, X-ray spectroscopy revealed the formation of O1s, Ag 3d, C1s, Mo 3d, and S2p in the 3D LSG_MoS2_Ag NPs-2.0 hybrid. Raman spectroscopy revealed an enhancement in the surface area of the 3D LSG_MoS2_Ag NPs-2.0 hybrid, which enhances the detection sensitivity. The 3D LSG_MoS2_Ag NPs hybrid was subsequently chemically modified and immobilised with an aptamer to interact with Troponin I on an impedimetric sensor. The 3D LSG_MoS2_Ag NPs hybrid showed high analytical performance, high specificity, and a ∼ 4-fold increment in selectivity, with a detection limit of 100 attomolar. This biosensor has a sensitivity of 31.45 µA mM−1 cm−2, stability of 87%, with a relative standard deviation for reproducibility of 3.8%.

Facile Methods for the Assembly of Large-Area Perovskite Solar Cells and Mini‑Module: A Step-by-Step Description of Layers Processing

Hybrid organic-inorganic perovskites have attracted interest in photovoltaic applications due to their excellent optoelectronic properties and low-temperature processability. From 2009 to 2021, lab-scale perovskite solar cells (PSC) reached a power conversion efficiency (PCE) of 25.7%, and a PCE of 17.9% for perovskite solar modules with an area of 800 cm2. Here, we present an investigation using three deposition techniques, spin-coating, blade-coating, and spraycoating, to process the charge transport layers and the active layer of perovskite solar cells onto 5 cm × 5 cm sized substrates, with device structure glass/fluorine-doped tin oxide (FTO)/c-TiO2/ meso-TiO2+Perovskite/2,2’,7,7’-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9’-spirobifluorene (spiro-OMeTAD) or poly(3-hexylthiophene) (P3HT)/Au. Large-area PSC achieved an opencircuit voltage of around 1.1 V and PCE of 6%. The power generated was sufficient to start a fan. Furthermore, the connection in series of two large-area PSCs generated a voltage of 1.9 V. Then, we developed a simple method for manufacturing a monolithic perovskite mini-module containing two series-connected PSCs without using laser-scribing processes (usually named P1, P2, and P3 processes). This mini-module delivered a voltage of 1.52 V. Both voltages (1.9 and 1.52 V) were enough to turn on a red (or yellow) light-emitting diode (LED). To our knowledge, this is the first scientific report describing the assembly of a large-area n-i-p perovskite single cell and mini-module in Brazil.

Zero-bias Bi-based perovskite image sensor arrays with direct laser-scribing process

We presented a 25 × 25 array imaging sensor based on Cs3Bi2Br9 photodetectors using a laser-scribing technique, which has the advantages of low cost, high accuracy, and being lithography-free.

On-the-Fly Short-Pulse R2R Laser Patterning Processes for the Manufacturing of Fully Printed Semitransparent Organic Photovoltaics.

Ultrafast laser patterning is an essential technology for the low-cost and large area production of flexible Organic Electronic (OE) devices, such as Organic Photovoltaics (OPVs). In order to unleash the potential of ultrafast laser processing to perform the selective and high precision removal of complex multilayers from printed OPV stacks without affecting the underlying nanolayers, it is necessary to optimize its parameters for each nanolayer combination. In this work, we developed an efficient on-the-fly picosecond (ps) laser scribing process (P1, P2 and P3) using single wavelength and single step/pass for the precise and reliable in-line patterning of Roll-to-Roll (R2R) slot-die-coated nanolayers. We have investigated the effect of the key process parameters (pulse energy and overlap) on the patterning quality to obtain high selectivity on the ablation of each individual nanolayer. Finally, we present the implementation of the ultrafast laser patterning process in the manufacturing of fully R2R printed flexible semitransparent OPV modules with a 3.4% power conversion efficiency and 91% Geometric Fill Factor (GFF).

Lightweight and flexible Cu(In,Ga)Se2 solar minimodules: toward 20% photovoltaic efficiency and beyond

Lightweight and flexible photovoltaic solar cells and modules are promising technologies that may result in the wide usage of light-to-electricity energy conversion devices. This communication presents the prospects of Cu(In,Ga)Se2 (CIGS)-based lightweight and flexible photovoltaic devices. The current status of flexible CIGS minimodules with photovoltaic efficiency values greater than 18% and future directions to enhance their efficiency values toward >20% are discussed. The effects of cell separation edges, which are formed through a mechanical, laser, or photolithography scribing process used to fabricate solar cells and modules, on the device performance are also discussed. We found that mechanically scribed CIGS device edges, which are present in conventional solar cells and modules, cause deterioration of device performance. In other words, further improvement is expected with appropriate passivation/termination treatment of the edges or replacing mechanical scribing with a damage-free separation process.

A laser-scribed wearable strain sensing system powered by an integrated rechargeable thin-film zinc-air battery for a long-time continuous healthcare monitoring

Wearable sensors with long cruising times without the need for an external wire-connected power supply are urgently required for a continuous physiological signal monitoring. Herein, we report the design and fabrication of a wearable all-in-one sensing system that integrates a sensitive strain sensor and a rechargeable zinc-air battery on the same laser-induced graphene (LIG) platform. The sensing electrode of the strain sensor, the catalytic air electrode of the zinc-air battery and the interconnection lines between the two are simultaneously fabricated through the same laser-scribing process on polyimide (PI) followed by pattern transfer to a flexible and stretchable polydimethylsiloxane (PDMS) substrate. In the sensor, the conductive porous LIG exhibits a high gauge factor (~2710.95), a wide detection range (~40%), and a well cyclic loading-unloading stability (>20,000 cycles). In the zinc-air battery, Co3O4 nanoparticles are in-situ laser-sintered on LIG to form an excellent electrode/electrolyte/air three-phased interfacing structure for a high catalytic performance, and a moisturized tetraethyl ammonium hydroxide (TEAOH)-KOH/polyvinyl alcohol (PVA) gel electrolyte tightly binds the Co3O4/LIG air electrode and zinc foil electrode together into an integrate thin-film energy device, which provides a high open-circuit voltage (~1.39 V) and a high specific capacity (712 mAh g−1 at 0.2 mA cm−2). For a proof-of-concept, an intelligent wristband based on the sensing system was fabricated and worn on the wearer’s wrist for a long-time continuous pulse monitoring of up to 10 h. The health state of the wearer can be depicted upon the acquired pulse waveforms. The developed LIG-based sensing system with a high internal powering capability will be promising in wearable sensing applications.