Pitaya-Structured Microspheres with Dual Laser Wavelength Responses for Polymer Laser Direct Writing

Patternable, high-precision, controllable wettability copper layers for 3D resin-based weather-resistant electronics and 3D liquid manipulation

The realization of 3D patterned metal layers with manipulable surface wettability has significant potential, especially in integrating microelectronics with weather resistance and multifunctional liquid manipulation. However, developing a facile and efficient method to bring it to fruition remains a great challenge. In this work, we proposed a novel 3D selective metallization strategy that combines stereolithography 3D printing with laser-induced selective metallization (LISM). Utilizing 355 nm UV or 1064 nm lasers, this strategy can prepare 3D conductive copper patterns (or circuits) with controlled wettability on various 3D-printed resin parts. The copper layer surface prepared via LISM formed microstructures similar to the papillae on the surface of a lotus leaf, and it spontaneously exhibited superhydrophobicity (156.6°) after aging in the air at room temperature. Superhydrophobic 3D circuits with self-cleaning, corrosion-resistant, and anti-condensation performance were successfully fabricated. By further treating the copper layer with a 355 nm UV laser, we realized the transformation of the superhydrophobic copper layer to a superhydrophilic state, enabling us to prepare high-precision superhydrophilic patterns or channels. A 3D self-driven flow channel was fabricated to successfully realize 3D liquid manipulation and small-scale chemical experiments.

In Situ Laser Direct Writing of Graphene-Based Layered Hybrid Materials with Superhydrophilicity

Laser-induced graphene (LIG) has attracted extensive attention as an electrode material. However, it usually exhibits limited electrochemical performance in many applications due to the limited electrical conductivity and charge storage properties. Herein, we proposed a simple and environmentally friendly strategy for in situ preparation of flexible Au/LIG/PI layered hybrid materials using laser direct writing. The transformation from hydrophobic to superhydrophilic of hybrid materials was successfully achieved. At a laser power of 6.0 W during laser reirradiation, the contact angle of the prepared Au/LIG/PI layered hybrid material was 0°. Characterizations confirmed a formed continuous Au layer covered on the porous LIG skeleton with a uniform distribution. The superhydrophilicity resulting from this unique microstructure greatly enhanced the electrochemical performance of the microsupercapacitors (MSCs) designed and fabricated based on Au/LIG/PI hybrid materials. Meanwhile, this MSC demonstrated excellent flexibility due to the PI substrate. The in situ preparation of superhydrophilic Au/LIG/PI layered hybrid materials provides a strategy for improving the performance of LIG-based MSCs, thereby enhancing their application potential.

Autocatalytic Laser Activator for Both UV and NIR Lasers: Preparation of Circuits on Polymer Substrates by Selective Metallization

In laser-induced selective metallization (LISM), conventional laser activators only work at a single laser wavelength. This study reported a new laser activator (MoO₃) very suitable for both 355 nm UV and 1064 nm near-infrared (NIR) lasers for the first time. When applying MoO₃ to polymers, the prepared Cu layer on laser-activated polymers showed a good conductivity (2.63 × 10⁶ Ω^-1·m^-1) and excellent adhesion. Scanning electron microscopy, optical microscopy, and resistance analysis revealed the excellent LISM performance of the polymer/MoO₃ composites, and the quality of the Cu layer prepared using the UV laser is much better than that using the NIR laser. The limit width of the copper wire prepared by the UV laser is as narrow as 30.1 μm. We also confirmed the mechanism of MoO₃ initiating electroless copper plating after laser activation to be the autocatalytic mechanism, which is very different from the conventional reduction mechanism. The effect of laser activation was only to expose the MoO₃ active species to the polymer surface. X-ray diffraction and tube experiments revealed that the activity of α·h-MoO₃ was higher than that of α-MoO₃. X-ray photoelectron spectroscopy indicated that a part of Mo⁶⁺ was reduced to Mo⁵⁺ during laser activations, leading to the increase of the oxygen vacancies in MoO₃ and possibly further enhancing the activity of MoO₃. Besides, the micro-rough structures caused by the laser on the polymer surface provided riveting points for successfully depositing the copper layer. The Ni-Cu, Ag-Cu, and Au-Ni-Cu layers were obtained via the continued deposit of other metals on the Cu layer. The resistances of these metal layers had much better stability than that of the neat Cu layer. Furthermore, the Au layer further enhanced the conductivity of the circuit. The proposed strategy is easy for large-scale industrial applications, which will greatly expand the application scenarios of the LISM field.