This study introduces a novel strategy for fabricating flexible nitrogen dioxide (NO₂) gas sensors based on Indium Oxide (In₂O₃) nanoparticles (NPs) employing selective reduction laser sintering (SRLS) technology. The SRSL technology utilizes ultraviolet (UV) laser selective reduction sintering to precisely and rapidly create oxygen vacancy (OV) defects in In₂O₃ NPs. These oxygen vacancies (OVs) enhance the active adsorption sites and contribute additional free electrons, significantly improving sensor performance at room temperature. The sensors demonstrate excellent response (S = 460.9 at 10 ppm), rapid response/recovery times (τ_resp/τ_reco = 27/570 s), and superior selectivity (response ratio > 400), in addition to robust resistance to light and humidity (under ppm-level NO₂ gas). The sensors also exhibit a low detection limit (200 ppb), a high signal-to-noise ratio (94.8 dB), and good long-term stability (25 days). Moreover, under photo-assisted conditions, the recovery speed of the sensors is further improved. This technology not only provides an innovative strategy for the development of high-performance flexible NO₂ gas sensors but also broadens the application potential of laser direct writing (LDW) technology in advanced materials and sensor fabrications.

This study introduces an innovative approach for fabricating flexible nitrogen dioxide (NO₂) gas sensors based on In2O3 nanoparticles (NPs) using selective reduction laser sintering (SRLS) technology. The SRLS technology enables specific chemical reduction reactions during the sintering process, achieving fabrication and control of oxygen vacancy defects and the porous structure in the In₂O₃ sintering region. The sensor exhibits exceptionally high sensitivity, fast response/recovery times, and superior selectivity for NO₂ gas detection, particularly at room temperature. Compared with traditional NO₂ gas sensor fabrication methods, this technology not only provides a potential way to fabricate highperformance NO₂ gas sensors but also further expands the application potential of laser direct writing (LDW) technology in the fields of advanced materials and sensor fabrication.

In this study, a convenient chitosan oligosaccharide laser lithograph (COSLL) technology was developed to fabricate laser-induced graphene (LIG) electrodes and flexible on-chip microsupercapacitors (MSCs). With a simple one-step CO₂ laser, the pyrolysis of a chitosan oligosaccharide (COS) and in situ welding of the generated LIGs to engineering plastic substrates are achieved simultaneously. The resulting LIG products display a hierarchical porous architecture, excellent electrical conductivity (6.3 Ω sq^-1), and superhydrophilic properties, making them ideal electrode materials for MSCs. The pyrolysis-welding coupled mechanism is deeply discussed through cross-sectional analyses and finite element simulations. The MSCs prepared by COSLL exhibit considerable areal capacitance of over 4 mF cm^-2, which is comparable to that of the polyimide-LIG-based counterpart. COSLL is also compatible with complementary metal-oxide-semiconductor (CMOS) and micro-electro-mechanical system (MEMS) processes, enabling the fabrication of LIG/Au MSCs with comparable areal capacitance and lower internal resistance. Furthermore, the as-prepared MSCs demonstrate excellent mechanical robustness, long-cycle capability, and ease of series-parallel integration, benefiting their practical application in various scenarios. With the use of eco-friendly biomass carbon source and convenient process flowchart, the COSLL emerges as an attractive method for the fabrication of flexible LIG on-chip MSCs and various other advanced LIG devices.

This study introduces a high-performance flexible temperature sensor prepared using laser-induced graphene (LIG) doped with nickel oxide (NiO) nanoparticles (NPs). Unlike conventional LIG surface doping methods, we developed a nickel oxide-doped LIG flexible temperature sensor by introducing NiO NPs into a polyimide (PI) precursor solution cured into a film followed by ultraviolet (UV) laser treatment. This approach achieves a more stable and uniform doping process while further improving the sensing performance of LIG-based temperature sensors. Over a prospective temperature detection range (30-100 °C), the sensitivity of the NiO-doped LIG temperature sensor is significantly improved from -0.064% °C-¹ to -0.079% °C-¹, an improvement of 19.3%, compared to that of the intrinsic LIG temperature sensor, while maintaining high linearity (R2 = 0.999) as well as excellent temperature stability and reliability. This research not only enhances the performance of flexible temperature sensors based on LIG but also paves new pathways for its industrial production in various application fields.

Flexible strain sensors play a crucial role in health monitoring, smart wearable devices, and human–machine interaction. Three-dimensional surface evaluation methods for strain sensors offer advantages by being closer to actual strain, featuring a larger working range, and being more suitable for multidirectional strain. In this study, a three-dimensional (3D) surface strain sensor based on polydimethylsiloxane/laser-induced graphene (PDMS/LIG) composite films has been developed. The electromechanical properties of this sensor, encompassing 3D strain range and sensitivity, can be adjusted by manipulating laser parameters and LIG patterns. The key to attaining these specific characteristics lies in the intentional design of crack types and orientations on the sensor's surface. Remarkably, the line-vertical (LV) sensor exhibits outstanding sensitivity with a GF of 211.3. The line-parallel (LP) sensor achieves a GF of 115.1. Additionally, it demonstrates a stretching range of 25% and maintains stable performance over an extensive number of strain/release test cycles (more than 3000 cycles). With these advantages, the 3D strain sensor can not only be applied in human activity monitoring but also monitoring pressure within microchannels in microfluidic chips, suggesting promising applications in the health and medical fields.

The fabrication of flexible pressure sensors with low cost, high scalability, and easy fabrication is an essential driving force in developing flexible electronics, especially for high-performance sensors that require precise surface microstructures. However, optimizing complex fabrication processes and expensive microfabrication methods remains a significant challenge. In this study, we introduce a laser pyrolysis direct writing technology that enables rapid and efficient fabrication of high-performance flexible pressure sensors with a micro-truncated pyramid array. The pressure sensor demonstrates exceptional sensitivities, with the values of 3132.0, 322.5, and 27.8 kPa^-1 in the pressure ranges of 0-0.5, 0.5-3.5, and 3.5-10 kPa, respectively. Furthermore, the sensor exhibits rapid response times (loading: 22 ms, unloading: 18 ms) and exceptional reliability, enduring over 3000 pressure loading and unloading cycles. Moreover, the pressure sensor can be easily integrated into a sensor array for spatial pressure distribution detection. The laser pyrolysis direct writing technology introduced in this study presents a highly efficient and promising approach to designing and fabricating high-performance flexible pressure sensors utilizing micro-structured polymer substrates.

In recent years, metal crack-based stretchable flexible strain sensors have attracted significant attention in wearable device applications due to their extremely high sensitivity. However, the tradeoff between sensitivity and detection range has been an intractable dilemma, severely limiting their practical applications. Herein, we propose a laser transmission pyrolysis (LTP) technology for fabricating high-performance flexible strain sensors based on (Au) metal cracks with the microchannel array on the polydimethylsiloxane (PDMS) surface. The fabricated flexible strain sensors exhibit high sensitivity [gauge factor (GF) of 2448], wide detection range (59% for tensile strain), precise strain resolution (0.1%), fast response and recovery times (69 and 141 ms), and robust durability (over 3000 cycles). In addition, experiment and simulation results reveal that introducing a microchannel array enables the stress redistribution strategy on the sensor surface, which significantly improves the sensing sensitivity compared to conventional flat surface sensors. Based on the excellent performance, the sensors are applied to detect subtle physiological signals, such as pulse and swallowing, as well as to monitor large-scale motion signals, such as knee flexion and finger bending, demonstrating their potential applications in health monitoring, human-machine interactions, and electronic skin.