Ultrafast Laser Plasmonic Fabrication of Nanocrystals by Molecule Modulation for Photoresponse Multifunctional Structures

Thermally Stable Oxide-Capsulated Metal Nanoparticles Structure for Strong Metal-Support Interaction via Ultrafast Laser Plasmonic Nanowelding

Strong metal-support interaction (SMSI) has drawn much attention in heterogeneous catalysts due to its stable and excellent catalytic efficiency. However, construction of high-performance oxide-capsulated metal nanostructures meets great challenge in materials thermodynamic compatibility. In this work, dynamically controlled formation of oxide-capsulated metal nanoparticles (NPs) structures is demonstrated by ultrafast laser plasmonic nanowelding. Under the strong localized electromagnetic field interaction, metal (Au) NPs are dragged by an optical force toward oxide NPs (TiO2). Intense energy is simultaneously injected into this heterojunction area, where TiO2 is precisely ablated. With the embedding of metal into oxide, optical force on Au gradually turned from attractive to repulsive due to the varied metal-dielectric environment. Meanwhile, local ablated oxides are redeposited on Au NP. Upon the whole coverage of metal NP, the implantation behavior of metal NP is stopped, resulting in a controlled metal-oxide eccentric structure with capsulated oxide layer thickness ≈0.72-1.30 nm. These oxide-capsulated metal NPs structures can preserve their configurations even after thermal annealing in air at 600 °C for 10 min. This ultrafast laser plasmonic nanowelding can also extend to oxide-capsulated metal nanostructure fabrication with broad materials combinations (e.g., Au/ZnO, Au/MgO, etc.), which shows great potential in designing/constructing nanoscale high-performance catalysts.

Ultrafast Laser 3D Nanolithography of Fiber-Integrated Silica Microdevices

Fiber-integrated micro/nanostructures play a crucial role in modern industry, mainly owing to their compact size, high sensitivity, and resistance to electromagnetic interference. However, the three-dimensional manufacturing of fiber-tip functional structures beyond organic polymers remains challenging. It is essential to construct fiber-integrated inorganic silica with designed functional nanostructures for microsystem applications. Here, we develop a strategy for the 3D nanolithography of fiber-integrated silica from hybrid organic-inorganic materials by ultrafast laser-induced multiphoton absorption. Without silica nanoparticles and polymer additives, the acrylate-functionalized precursors can be locally cross-linked through a nonlinear effect. Followed by annealing at low temperature, the as-printed micro/nanostructures are transformed to high-quality silica with sub-100 nm resolution. Silica microcantilever probes and microtoroid resonators are directly integrated onto the optical fiber, showing strong thermal stability and quality factors. This work provides a promising strategy for fabricating desired fiber-tip silica micro/nanostructures, which is helpful for the development of integrated functional device applications.

Flexible Copper-Based Thermistors Fabricated by Laser Direct Writing for Low-Temperature Sensing

With the flexibilization tendency of traditional electronics, developing sensing devices for the low-temperature field is demanding. Here, we fabricated a flexible copper-based thermistor by a laser direct writing process with Cu ion precursors. The copper-based thermistor performs with excellent temperature sensing ability and high stability under different environments. We discussed the effect of laser power on the temperature sensitivity of the copper-based thermistor, explained the sensing mechanism of the as-written copper-based films, and fabricated a temperature sensor array for realizing temperature management in a specific zone. All of the investigations have demonstrated that such copper-based thermistors can be used as candidate devices for low-temperature sensing fields.

Micromachining of High-Quality PMN-PT/Epoxy 1-3 Composite for High-Frequency (>30 MHz) Ultrasonic Transducer Applications

Fabricating PMN-PT composites, the core component of high-frequency (> 30 MHz) transducers, remains challenging due to their poor machinability and ultrasmall kerfs. This urgent problem is significantly impeding the development of PMN-PT ultrasonic transducers for use in clinical research, biomedical sciences, and nondestructive testing (NDT). In this study, high-quality PMN-0.3PT/epoxy 1-3 composites at 30 and 50 MHz were manufactured using a modified picosecond (1.5 ps) laser technique. Their performance was thoroughly analyzed, which was comparable to that with low-stress dry plasma etching. There were fewer microcracks around PMN-PT pillars. The minimum kerf was less than [Formula: see text], and the highest aspect ratio was larger than 7.5. The microdomain morphology and hysteresis loops of PMN-PT pillars further confirmed that composites still maintained excellent piezoelectric performance and suffered fewer damages during laser cutting. The characterization results exhibited a large electromechanical coupling (>0.77), a high dielectric constant (>1600), and a relatively low acoustic impedance (< 17 Mrayls). The ultrasonic transducers with center frequencies of 30 and 50 MHz were designed and prototyped to validate the performance of composites. The transducers showed broad bandwidth (>80%), high two-way insertion loss (IL) (>-23 dB), and imaging resolution superior to [Formula: see text]. Finally, the C-scan experiments of IC chips were also used to further illustrate the applicability of transducers. These encouraging results further demonstrated that ultrafast laser technology will bring more accessible and affordable methods for fabricating high-frequency PMN-PT composite transducers with excellent performance.