This study explores the effects of laser shock peening and deposition direction (uni-directional and bi-directional), evaluated with three different build regions, such as bottom (BR), middle (MR), and top regions (TR). In addition, the impact of LSP on microstructure and mechanical properties of SS308L material fabricated using directed energy deposition-Arc (DED-Arc) was studied. The novelty of this work lies in the comparative analysis of LSP-treated versus untreated SS308L samples and its impact on enhancing mechanical performance. LSP treatment significantly improved UTS, YS, hardness, and reduced porosity of the material, with bi-directional deposition samples showing the highest improvements. In the comparison analysis of two different depositions with LSP on top regions, it has been observed that the microstructure of the DED-Arc-created SS308L material was vertically growing columnar and equiaxed interdendritics, and further refined the grain structure by LSP process. Microstructural analysis revealed a refined grain structure with vertically growing columnar and equiaxed dendrites after LSP treatment, enhancing the material’s overall performance. These results suggest that LSP significantly enhances the mechanical properties of DED-Arc-manufactured SS308L, making it a promising technique for improving material quality in additive manufacturing.

In this growing technological world, laser decal transfer has emerged as a groundbreaking technique due to its ability to offer high precision, material versatility, and design freedom. While various combinations of metals have been explored for applications ranging from aerospace and biomedical devices to micro-electromechanical systems (MEMS), it works on conventional printing processes that rely on wire or powder as raw materials, which limit their applicability in certain end-use cases. In contrast, laser decal transfer enables the precise deposition of materials without phase changes, making it particularly suitable for advanced applications where chemical and functional integrity must be maintained. Most MEMS devices are fabricated using either lithography-based processes or microfabrication systems, both of which involve phase change during fabrication. This phase change often alters the chemical and functional properties of the devices, highlighting the need for a fabrication method that preserves the original material characteristics. With advancements in technologies, a thin film-based laser decal transfer setup is yet to be fully explored for printing thin-film materials in pixelated form over substrates, enabling substrate- and material-independent processes. The present work focuses on the development of a laser decal transfer-based printing process using thin film as feed material for the fabrication of MEMS devices for piezo-tribo hybrid applications. Surface modification is explored to enhance static charge retention over surfaces. Initially, a silicon wafer is coated with a sacrificial layer over which a piezo-ceramic (ZnO) is sputtered to develop a seed layer. A CO2 laser (λ=10.6 μm) is utilized in the proposed work, with a detailed investigation of laser processing parameters conducted for effective control over piezo-ceramic transfer and selective positioning. The influence of laser fluence and standoff distance is analyzed, and laser pulse overlap's effect on heat-affected zones and material transfer is thoroughly examined. Based on optimized parameters, the selective control and transfer of ceramic onto solid and flexible substrates are demonstrated. The selectively transferred nanoparticles in various patterns are further grown using a hydrothermal technique. Material characterization is performed to confirm the pixelated transfer of ceramic without phase transfer, and the surface adhesivity of transferred material is analyzed using a scotch tape test. Finally, a ZnO-FEP-based piezo-tribo hybrid device is fabricated, tested for both piezoelectric and triboelectric responses, and further explored for hybrid device applications. The proposed technology of laser decal transfer has significant potential for the complex printing of sensors without directly affecting the material, allowing for controlled gradient-based properties. This approach holds great promise for futuristic technologies enabling the selective printing of functional piezoelectric and triboelectric sensors.

Micro-manufacturing processes are a burgeoning field of research, especially as Industry 4.0 drives a trend towards miniaturization. Laser-assisted manufacturing has gained prominence for advanced and additive manufacturing, demonstrating significant potential for functional applications. Laser µ-3D printing, a subset of laser-assisted manufacturing, is notable for being a non-contact, one-step, and high-resolution process that efficiently saves time and cost. However, achieving optimal transfer quality deposits remains a challenge. This manuscript focuses on the critical parameter of laser wavelength and its processing parameters for effective material transfer. ZnO ceramic, an exceptional material for opto-electronics applications, is sputtered using RF sputtering on a PDMS sacrificial layer coated silicon wafer, with a 10.6 µm CO2 laser investigated for material ejection effects and functional variations on ZnO ceramic. Additionally, a 532 nm laser source is explored by sputtering ZnO over ITO-coated glass. Key parameters such as pulse overlap, laser fluence, and stand-off distance are studied. Optimal parameters of 11.5 cm SOD, 75 J/cm2 laser fluence, and 65% laser fluence were identified with the 10.6 µm CO2 laser, while short pulse lasers are being investigated. The impact of processing parameters on feature size and controllability is examined, highlighting their application in opto-electronics through UV-Visible outputs.

Nickel-Titanium (NiTi) alloys are well-known for their remarkable shape memory effect and superelasticity, making them highly desirable in various industrial applications such as smart actuators, adaptive valves, and precision fasteners. This study focuses on the thermo-mechanical and microstructural evolution of NiTi alloys produced using Wire Arc Additive Manufacturing (WAAM), a technology known for its ability to create complex geometries efficiently. The research examines the impact of annealing followed by furnace cooling on the mechanical behavior and structural integrity of WAAM-deposited NiTi alloys. Tensile testing was conducted to assess the static mechanical properties, including strength and ductility, crucial for industrial applications. Following a detailed analysis, the findings reveal that the heat treatment significantly enhances the properties of WAAM-produced NiTi parts. The transformation peaks associated with the Ti2Ni phase reduced significantly, indicating a higher formation of the desired NiTi phase. Mechanical properties improved notably, with the ultimate tensile strength (UTS) increasing from 199.13 MPa to 286.53 MPa in the austenite phase and from 237.53 MPa to 404.8 MPa in the martensite phase. Microstructural analysis revealed an increase in grain size from 9.04 µm in the as-deposited condition to 12.81 µm after annealing, while hardness decreased from 337.3 Hv to 302.54 Hv, suggesting improved ductility and strength. These findings highlight the effectiveness of heat treatment in controlling the mechanical, thermal and microstructural characteristics of NiTi components, making them more suitable for challenging industrial settings.

In this letter, we present a unique method to improve the output performance of ZnO-based flexible piezoenergy harvesters (FPEHs). Halide dopants (Cl, Br) are infused into ZnO nanorods (NRs) to increase lattice distortion along the c-axis. This facilitates charge separation, which improves the output performance of halide-doped ZnO FPEHs. This technique confirmed that the size and concentration of the dopants have a significant impact on lattice distortion along the c-axis in halogen-doped ZnO NRs. By doping the halide elements, the lattice distortion along the ZnO c-axis could be tuned from a contractive to an elastic state. This modulation was driven by the variation in ionic size and doping concentration of halide elements, which yielded an enhancement in the performance of ZnO FPEHs. The pristine ZnO NRs exhibited an output voltage of 2.24 V and a current of 272.68 nA, yielding a maximum power of 610.8 nW. In contrast, ZnO:Cl NRs demonstrated a piezoelectric voltage of 3.41 V and a piezoelectric current density of 323.43 nA/cm2, reaching a peak power output of 1.1 µW. ZnO:Br NRs exhibited an even higher piezoelectric voltage of 4.55 V and a current of 367.79 nA, achieving a maximum power of 1.67 µW. Further enhancement in piezoelectric performance was observed when the NaBr doping concentration was increased to 20 mM, resulting in a piezovoltage of 4.84 V, a piezoelectric current of 447.63 nA, and a peak power of 2.17 µW. This approach of inducing the lattice distortion via halide dopants could be applied to design piezoelectric devices with improved efficiency at a low cost.

3D printing or additive manufacturing has gained popularity due to its high innovation potential, process improvement, and design freedom in industries such as aerospace, dental, medical, and automotive. A detailed investigation into thin film as a feedstock for printing maskless MEMS structures is an important area of current research. In this work, we explore the selective positioning of ZnO ceramic over a NiTi interdigitated structure on an ITO-coated glass substrate using the laser decal transfer technique. A CO2 laser (λ = 10.6 µm) is employed, and the effects of laser processing parameters—including laser fluence, laser pulse overlaps, and stand-off distance—are systematically analyzed. Key experimental findings indicate that a laser fluence of 75 J/cm2 optimally facilitates ZnO transfer while avoiding material burning. A stand-off distance of 12.5 cm allows effective material transfer, whereas off-focus conditions hinder ZnO deposition. Additionally, an optimal laser pulse overlaps of 65% achieves a balance between continuous material transfer and minimal heat-affected zone. The transferred ZnO seed layer, approximately 5 µm thick, is further hydrothermally grown into well-structured ZnO nano-rods, confirmed through SEM and XRD analysis, which identifies a hexagonal wurtzite crystal structure. Finally, using optimized parameters, the feasibility of multi-material transfer is demonstrated, with successful ZnO deposition on a NiTi interdigitated structure (600 µm feature size), forming a layered structure. The proposed laser micro-3D printing via laser decal transfer offers significant advantages for fabricating complex sensors with controlled gradient-based properties.

In Laser decal transfer process, the materials are printed in micron-sized dots without changing its phase from thin film coated substrate (donor substrate). The pulsed laser irradiates the donor substrate opposite to the coated side and transfers the material in the same phase to another substrate kept very close to the donor substrate. The process has shown its potential for printing microsensors without any changes in physical and functional properties during the printing process for the electronics components. Generally, ZnO-based patterned structure is still challenging for the existing manufacturing techniques without hampering its functionality in the sensing application. In this work, an attempt has been made to print ZnO structure in solid phase using maskless µ-3D printing using a long-pulsed CO2 laser. A two-dimensional numerical model in COMSOL Multiphysics is developed to estimate the temperature induced by the laser irradiation on the sacrificial layer, and energy conservation is applied to estimate the particle’s velocity. A deformed mesh geometry is used to predict the ablation depth of the sacrificial layer after the laser irradiation. The deformed geometry shows the ablated area in the sacrificial layer, and the temperature induces a different time frame. The ZnO ceramic film is coated on the sacrificial layer followed by the laser µ-3D printing of ZnO on silicon wafer using CO2 laser at three laser fluence, i.e., 530 mJ/cm2, 1030 mJ/cm2, and 1530 mJ/cm2 with 90% pulse overlap. The ejection of ZnO from substrate is visualized using a high-speed camera by shadowgraphy techniques. The ejection mode is defined based on the deviation of the particle from the laser beam direction.

Self-powered sensors detect a variety of crucial parameters for industrial processes without any external power source for Industry 4.0. It has capabilities to acquire, analyze, and make decisions on real-time data, these sensors are essential for the advancement of automated production systems and smart factories. In this regard, Triboelectric nanogenerators (TENGs) have potential to provide effective solution as self-powered vibration sensor for continuous monitoring of machine tools. Different techniques have been used to enhance the performance of TENG such as material doping, chemical etching, ion injection, etc. However, laser surface texturing is a low-cost, contact less, efficient technique which can be used for improving the response of TENG-based self-powered vibration sensors. In this context, Laser Induced Backside Texturing is a laser micro texturing approach to improve the electrical performance. It induces waviness and surface roughness, which leads to increased surface charge density and triboelectrification capabilities. In this work, laser micro texturing was performed using with 405 nm wavelength semiconductor diode laser to generate line pattern texture on the Fluorinated Ethylene Propylene (FEP). Laser textures TENG (LT-TENG) was developed with laser textured FEP as tribonegative material and pristine Aluminium as tribopositive material, the open-circuit voltage, short-circuit current and power density achieved 23 %, 41 %, and 47 % enhancement respectively, generating 794 V, 44 µA, and 2371.6 µW/cm2. This increase in output leads to an increased sensitivity of the sensor. When mounted on the machines, LT-TENG was able to detect their working state, vibration frequency, and harmonics i.e. 46, 92, 184 Hz for the vacuum pump and 140, 280, 410 Hz for the heat gun. These detected vibration frequencies, and their harmonics were similar to the frequencies detected by the commercial accelerometer (CTC AC115), confirming potential use of LT-TENG as a low-frequency vibration sensor. The developed LT-TENGs was integrated with the Internet of Things (IoT) supported microcontroller, which collects real-time data for continuous monitoring and analysis for machine health monitoring in smart devices.

Bioimplants have emerged as transformative tools in modern healthcare, revolutionizing the treatment of various medical conditions and significantly improving patients' quality of life. In the realm of orthopaedics, joint replacements, including hip and knee implants, cardiovascular bioimplants, and dental implants have set new standards for durability and biological functionality. These implants are prone to fail due to inadequate loading conditions, mismatch in biocompatibilities, faster degradation by cell tissues, excessive wear by mating bones, and low corrosion resistance in long period of times which need to be resolved before implanting into in human bodies. The bio-implants are mainly fabricated by metallic materials or ceramics such as titanium, magnesium, stainless steels, zirconium oxide and aluminium oxide which shows similar strength to natural body parts. The functionalities of these structural materials can be improved by surface modification such as surface coating, texturing, and engraving to increase the durability of bioimplants when it is service. The surface coating is performed with thin layer of materials having high bio-integration capabilities that leads to increase in biocompatibility and bio-functionality while maintaining the promising properties of structural materials. The surface of the bioimplants plays significant contribution towards the interaction of human body tissues with bioimplants hence the biocompatibility, cell adhesions and its interaction can be improved by surface texturing without changing its desired geometrical structures and its structural strength. The surface engraving is deployed on the bioimplant provide the information about the materials, surface treatment and the fabrication process of the bioimplant before installing into the human bodies. In this chapter focusses on methods and other important details of surface coating, texturing, and engraving of bioimplants.

In this work, Laser-induced forward transfer (LIFT) is deployed for micro-3D printing to deposit NiTi alloy using CO2 laser (λ = 10.6 µm) in the form of the solid phase. The transparent silicon wafer (with laser wavelength) is used as the donor substrate and Polydimethylsiloxane (PDMS) as a sacrificial layer that absorbs the laser energy and induces a thrust force for the transfer mechanism. Over the sacrificial layer, NiTi alloy thin film is deposited with DC sputtering technique at working pressure 2 × 10–3 mbar and stand-off distance 5 cm. After the donor preparation, the micro-3D printing is deployed at laser fluences 1270 mJ/cm2 at different (100 mm, 130 mm, 160 mm) focusing distances from the lens (f = 100 mm). It is observed that due to the high energy density of the laser beam at 100 mm distance, the pixel gets ablated from the top surface while at 160 mm distance the energy is insufficient for the complete transfer. Then the spot overlap is varied with 30%, 60%, and 90%, and observed that with an increase in overlap % the pixel density increases leading to a continuous line pattern. The deposited geometry's surface morphology has been analyzed using a scanning electron microscope (SEM) and optical microscope. EDS is performed to confirm the elemental composition of the deposition and observed that Ni and Ti are nearly equal in wt % with Si, and C due to the dissociation of PDMS sacrificial layer.

Metal additive manufacturing deploys metallic powder or wire as a feedstock to fabricate metallic parts by direct fusion in a layer-by-layer manner. Wire feedstock-based additive manufacturing provides certain advantages such as a higher rate of deposition, high density, and lower material wastage with less capital required. This study reports the Wire Arc Additive Manufacturing (WAAM) of Commercially Pure Titanium (CP Ti) and its microstructure, mechanical properties, and biocompatibility. A single-track deposition is performed to know the optimum parameters for wall structure deposition. The heat treatment is carried out to achieve desired phase transformation followed by Laser Shock Peening (LSP) as post-processing. The as-built samples showed dominant α-phase + β-phase while the content of β-phase increased after heat treatment at 900 °C. the thickness of LSP affected layer is observed to be 43.4476 μm along the cross-section. The hardness reduced after heat treatment and increased after LSP post processing. LSPed zone exhibited higher average hardness of ∼225 HV while that of the 30 min and 90 min heat treated samples is ∼180 HV0.1and ∼160 HV0.1, respectively. A better antibacterial test is performed to study the inhibition zone on samples. The LSPed sample surface in the biocompatibility test. The LSPed samples showed better antibacterial effect.

Shape memory effects were studied in a NiTi / Kapton composite produced by deposition of a thin layer of NiTi on a Kapton substrate by electronic beam evaporation. It was shown that after preliminary deformation by bending at room temperature, the composite demonstrated strain recovery on heating. An increase in preliminary strain increased the recoverable strain the maximum value of which was 2.1 %. The two-way shape memory effect was not observed due to a small thickness of the NiTi layer that did not exceed 300 nm. It was shown that the recoverable strain variation on cooling and heating under a stress was not observed due to the polymer creep on heating. The functional properties of the NiTi / Kapton composite produced by e-beam evaporation were compared to the behaviour of the NiTi / Kapton composite produced by the flash evaporation technique. It was shown that the value of the shape memory effect was comparable for both composites, whereas the irreversible strain was smaller in the samples produced by e-beam evaporation.

Laser-induced graphene is one of the advanced manufacturing techniques for transforming a non-biodegradable thermoset plastic (i.e., polyimide) to useful three-dimensional graphene. To analyze its effectiveness and improve usefulness of the novel technique it is essential to analyze the laser interaction and its variations that affects the associated properties. The present work focuses on developing carbon dots by Gaussian laser beam at varying irradiation time at constant spot diameter of ~ 567 µm to examine the modified structural relationships and their consequences on its functional properties. The development of highly localized and non-uniform energy distribution induces functional gradients across the laser spot as observed from the simulation and experimental results. The maximum observed temperatures from simulation results are 1913 °C, 2077 °C, and 2799.93 °C, respectively, at the center of the spot and the temperature varies spatially across the spot. Raman Mapping presents the modification in synthesized graphene spatially suggesting laser irradiation time having a significant effect in the functional properties. Spatial spot variation suggests that defect-to-graphitization ratio reduces for all laser irradiation from end of spot to the center. The properties of synthesized graphene also varied in average in-plane crystalline size increased from 34.5 ± 5 to 43.5 ± 17 nm in samples A and B, respectively. However, the crystallite size decreases to 37 ± 9 nm in sample C due to high temperature over the surface that leads to vaporization of carbon atom from the surface. These findings hold direct relevance for electro-chemical and flexible-electronics applications. Graphical abstract: [Figure not available: see fulltext.].

In this work, zinc oxide–based piezoelectric nanogenerator (PENG) over the flexible Kapton polyimide (PI) substrate is developed. The device performance is improved by laser texturing of PI substrate, which increases the effective surface area of PI and adhesivity of ZnO thin film with PI substrate to improve the reliability and life span of the device. The untextured PI-based PENG generates a peak-to-peak output voltage, current, and power of 6 V, 420 nA, 2.42 μW, respectively, which increases to 15.8 V, 790 nA, and 12.51 μW, respectively, on using textured PI obtained by 60% laser spot overlap. On further increasing the laser spot overlap to 80%, the peak-to-peak output voltage, current, and power improve to 22.2 V, 1210 nA, and 26.88 μW, respectively. Therefore, as compared to the untextured-PI-based PENG, laser-textured-PI-based PENG is a promising candidate for energy-harvesting applications.

Graphene, is one of the prominent materials in device fabrication due to its high conductive and high flexural strength for electrodes/device applications. The latest technique for graphene synthesis i.e. carbonization of polyimide by laser patterning has received much attention because of its capability to create various functional materials and flexible devices. The requirement of graphene demands larger volume production where laser-induced graphene (LIG) by consideration of pulse overlap could prove to be the solution if a recipe is prepared through appropriate optimization. The present study focused on the CO2 laser (λ = 10.6 µm) interaction with polyimide by generating raster pattern with varying pulse overlap in linear direction. The raster pattern is fabricated at different laser energies and pulse overlap with a constant 30% line overlap between two consecutive lines, in the lateral direction, for synthesizing LIG at relatively low laser power. Various combinations of laser fluences (46 J cm−2, 56 J cm−2, 66 J cm−2) and pulse spot overlap (60%, 70%, and 80%) were used for the polyimide carbonization. Both experimental and numerical simulation (using ComsolTM) results present an insight that optimal control of laser pulse overlap shows significant effect on crystallinity and electrical resistivity of synthesized graphene. The macroscopic quality of the raster pattern is investigated through the optical microscope. Detailed Raman spectro-microscopic analysis is carried out to study the defect to graphenization ratio and its impact on the properties of graphene synthesized. Through Raman analysis, the average in-plane crystallite length of graphene synthesis was observed from 27.732 ± 4-37.132 ± 6 nm. At last, a resistive type strain sensor was fabricated to check the stability of LIG and its reliability for repetitive loading conditions. The pulse overlap photo-thermal model, and its finite element analysis implementation presents better understanding towards optimizing the promising technique towards synthesizing LIG.

In this work, Shape Memory Alloy (SMA) based flexible mirrors were fabricated using the E-beam evaporation technique with varying pre-strain on the Kapton polyimide substrate during deposition. The mirrors are crucial for scanning and light beam deflection in MEMS applications. The fabricated bimorphs were investigated for actuation characteristics and reflectance as a mirror in the visible light range. The maximum displacement observed was 75 µm for 1% pre-strained bimorph. The study of shape recovery ratio revealed that bimorph without any pre-strain has the highest shape recovery of 1.637. For mirror application, the reflectance of the bimorph is of prime importance, which was determined by the UV-Visible study of fabricated samples. The maximum reflectance observed was 98.3% for both unstrained and 1% pre-strained samples. Energy Dispersive X-ray Spectroscopy (EDS) study displays the compositional variation of the deposited film.

Laser decal transfer based µ-3D printing is a new technique for microscale fabrication of the MEMS devices. The freedom towards the thin metal film, polymers, biomolecules, nanoparticles set off the new direction for fabrication of sensors and actuators. In this work, a NiTi based strain sensor is printed on PET substrate using µ-3D printing. Three and five-layer of strain gauge are printed, and its response are analysed by tensile loading. The resistance of the printed strain gauge are 220 ± 10 kΩ and 88 ± 8 kΩ while the gauge factor found to be 9 ± 3 and 13.5 ± 1.5 respectively.

The paper is aimed to study the functional properties in the layered NiTi sample produced by wire arc additive manufacturing (WAAM). The experimental studies were carried out using two types of samples: including the Ti–rich and Ni-rich layers or including Ni-rich layers only. The obtained results showed that the existence of the Ti–rich NiTi layer affected the two-way shape memory effect, which was two times higher than the sample including the Ni-rich NiTi layers only. This was due to the additional internal stress formed during preliminary deformation on the border between the Ti–rich and Ni-rich NiTi layers. It was found that the existence of the Ti–rich NiTi layer suppressed the initiation of superelastic response because the stress-induced martensite remained stable on unloading. It was observed that excluding the Ti–rich NiTi layer from the deformation allowed to reveal the superelasticity effect. It was also noticed that the value of the maximum recoverable strain did not exceed 4%, which was 2–2.5 times less than in the NiTi samples produced by conventional technologies. It was assumed that a small recoverable stain was caused by the texture and a small strain up to failure.

Laser-induced forward transfer (LIFT)-based micro-3D printing is a process in which the pulsed laser beam is used to transfer the material from thin-film deposited substrate (donor substrate) to the target substrate by inducing a high-pressure gas between the thin film and substrate. This study is focused on printing NiTi shape memory alloy using micro-3D printing for the continuous line pattern deposition. NiTi material is coated in the thin film via sputtering process, and the line pattern is deposited by CO2 laser at a wavelength of 10.6 μm for the transfer process. Numerical simulation is performed to analyze the interface temperature between the thin film and sacrificial layer. The optimized laser fluences for 1.5 μm and 3 μm sacrificial layer thicknesses are 770 mJ/cm2 and 2300 mJ/cm2, respectively. The printed pixel size decreases with an increase in the overlap, and the adhesion of pixels (with substrate) increases with an increase in the target substrate temperature. The transferred pixels are characterized using energy dispersive spectroscopy analysis and X-ray diffraction techniques. The study paves a way for the successful micro-3D printing of NiTi for potential microdevice fabrication.

Laser-induced forward transfer (LIFT) is a non-lithography, nozzle-free printing technique widely used to transfer different materials with high resolutions. It can deposit functional material without phase change to fabricate actuators, transducers, and other MEMS devices. In this work, LIFT is deployed to deposit NiTi shape memory alloy using CO2 laser (λ = 10.6 µm) in the form of the solid phase. The silicon wafer is used as the donor substrate since it is transparent to the CO2 laser wavelength, while the silica glass is used as an acceptor substrate. The donor substrate is coated with the Polydimethylsiloxane (PDMS) as a sacrificial layer that absorbs the laser energy and induces a thrust force for the transfer mechanism. Over the sacrificial layer, NiTi Shape memory alloy thin film is deposited with DC sputtering technique at working pressure 2 × 10–3 mbar and standoff distance 5 cm. After the donor preparation, the LIFT is deployed at various laser fluences and SOD to transfer NiTi on the silica glass substrate. The deposited geometry’s surface morphology has beenanalyzed using a scanning electron microscope (SEM) and optical microscope. The functionality of the deposited materials has been analyzed using Differential Scanning Calorimetry (DSC).

Wire Arc Additive Manufacturing (WAAM) is an emerging field of manufacturing due to its degree of freedom for large-size components with complex geometry and high deposition rate. However, owing to higher heating and sudden cooling cycles during the deposition, tensile residual stress is generated in the fabricated sample. In this work, WAAM and Laser Shock Peening (LSP) are deployed to improve the mechanical and functional properties of Ni–Ti shape memory alloy. Ni–Ti wall structure was fabricated in five layers with a voltage of 16.5 V and wire feed rate of 5.5 m/min for 10 s delay after each layer. Laser shock peening was performed with the laser power of 1 W. The as-deposited WAAM and LSP samples were appraised its mechanical and functional properties using an optical microscope, microhardness, and Differential scanning calorimetry (DSC). The optical microscope images of LSP samples revealed the grain refinement compare to the as-deposited sample. During the LSP process, the generated laser-plasma induces the compressive residual stress that enhances the microhardness values of the laser peened examples.

In the present study, a novel technique to replace conventional honing with a laser hatch patterning accompanied by nitriding called pulsed laser hatch patterning and nitriding (PLHN) process has been identified and reported in detail. Effect of process parameters like laser wavelength (532 and 1064 nm) and N2 gas flow rate (5–35 L/min) on the nitride layer quality, average roughness, hardness, and elevated temperature tribological performance of A356 cast Al alloy has been investigated. The formation of a thin AlN layer was confirmed from (GIXRD and XPS) analysis. The crack-free nitride layer was produced with a maximum thickness of 13.48 ± 0.53 µm, and 11.35 ± 0.34 µm using laser wavelengths 532 nm (at 15 L/min) and 1064 nm (at 25 L/min), respectively. At these optimized process parameters, the PLHN specimen processed at 532 and 1064 nm laser wavelengths showed a maximum of 212.57 and 144.73% increment hardness values as compared to the base material (1.52 Gpa). While the wear rate (200 °C) was reduced by 43.25% and 36.48% for the PLHN specimen processed at 532 nm and 1064 nm, respectively in comparison with the base material.

This paper aimed to study the influence of the substrate and the arc voltage on the structure and functional properties of the NiTi shape memory alloy produced by wire arc additive manufacturing (WAAM). The gas metal arc based WAAM process was used for the deposition of 3-layered NiTi walls on a titanium or steel substrate at different arc voltages using a Ni50.9Ti49.1 wire. It was found that in the sample deposited on the Ti substrate, the Ti2Ni phase appeared and the Ti concentration in the NiTi phase increased to 50.5 at.%. An increase in the arc voltage influenced the volume fraction of Ti2Ni precipitates in the 1st layer but hardly affected the chemical composition of the NiTi phase in all layers as a result, the martensitic transformation temperatures do not depend on the arc voltage. Therefore, the deposition of the Ni-rich NiTi wire on a Ti substrate allowed for the production of the Ti-rich NiTi walls undergoing the martensitic transformation and demonstrated the shape memory behaviour at high temperatures. An increase in the arc voltage hardly affected the shape memory behaviour but decreased the strain up to failure due to an increase in the volume fraction of the brittle Ti2Ni phase, which in turn facilitated the formation of cracks during deformation. In the sample deposited on the steel substrate, the NiTiFe solid solution and Ti-C, Ni3Ti4, and Ni3Ti2 precipitates formed in the 1st layer. An increase in the arc voltage led to an increase in the Fe concentration in the NiTiFe solid solution from 17 at.% to 42 at.% in the 1st layer. From layer to layer, the Fe concentration decreased; however, it remained larger than 1.5 at.% and completely suppressed the martensitic transformation and the shape memory effects in the NiTi sample deposited on the steel substrate.

ZnO nanostructures gained much attention for the micro/nano devices fabrication, but it is facing challenges in the deposition on the flexible substrate for optoelectronics applications. In the present work, Laser-Induced Forward Transfer (LIFT) was deployed for the deposition of the ZnO nanostructures on the flexible polyethylene terephthalate (PET) sheet using Indium Tin Oxide (ITO) sacrificial layer. The process window was developed for the laser parameters in COMSOL Multiphysics simulation for estimating the temperature distribution. Three different laser wavelengths (355 nm, 532 nm, and 1064 nm) and laser fluence ranging from 100 to 550 mJ/cm2 were used in the numerical simulation. Subsequent to the numerical simulation, the LIFT process was deployed at three different laser fluence (100, 250, and 550 mJ/cm2) with 355 nm wavelength for the transfer of ZnO nanorods. SEM images reveal that the higher fluence (550 mJ/cm2) melts the donor materials and degrades the quality of deposition. During the experiments, the time-resolved imaging measured the velocity of the deposited materials and observed that the velocity of 960 m/s, 200 m/s, and 90 m/s is achieved at a laser fluence of 550, 250 and 100 mJ/cm2, respectively. The XRD analysis and PL analysis show better structural and optical properties of deposited ZnO nanostructures as compared to previously published work available in the literature.

The gas metal arc welding (GMAW) based wire arc additive manufacturing (WAAM) process has been employed to deposit 5-layered NiTi alloy on the Titanium substrate using Ni50.9Ti49.1 wire as the feedstock. The heterogeneity of the piled up layers has been evaluated in terms of the variation in microstructure, composition and phases present. The melting of the Ti substrate under the first layer led to a substantial increase in Ti concentration in the melt during the deposition of the first layer and facilitated the formation of Ti-rich NiTi/Ti2Ni mixture during the solidification. In the 2nd – 5th layers columnar grains appeared in the inner space, whereas equiaxed grains formed on the top of the layers. The chemical composition of the 1st – 3rd layers differed from the nominal composition of the feedstock wire i.e. the layers in proximity of the substrate had lesser Ni concentration. As the result, the temperatures of the B2 ↔ B19’ martensitic transformation were different across the layers and the start temperature of the forward transformation changed from 73 °C (1st layer) to −16 °C (5th layer). Using the EDX and calorimetric data, the Ni distribution in each layer was determined and its influence on the martensitic transformation temperatures was discussed in detail. The difference in Ni concentration has made various layers to be present in different states (martensite or austenite) at room temperature. In this case, the layers (2–4) were deformed by different mechanisms during tension at room temperature. The deformation of the layers by reversible mechanisms was confirmed by the shape memory effect on heating of the pre-deformed NiTi sample produced by WAAM.