High-density interconnect (HDI) soft electronics that can integrate multiple individual functions into one miniaturized monolithic system is promising for applications related to smart healthcare, soft robotics, and human-machine interactions. However, despite the recent advances, the development of three-dimensional (3D) soft electronics with both high resolution and high integration is still challenging because of the lack of efficient manufacturing methods to guarantee interlayer alignment of the high-density vias and reliable interlayer electrical conductivity. Here, an advanced 3D laser printing pathway, based on femtosecond laser direct writing (FLDW), is demonstrated for preparing liquid metal (LM)-based any layer HDI soft electronics. FLDW technology, with the characteristics of high spatial resolution and high precision, allows the maskless fabrication of high-resolution embedded LM microchannels and high-density vertical interconnect accesses for 3D integrated circuits. High-aspect-ratio blind/through LM microstructures are formed inside the elastomer due to the supermetalphobicity induced during laser ablation. The LM-based HDI circuit featuring high resolution (∼1.5 μm) and high integration (10-layer electrical interconnection) is achieved for customized soft electronics, including various customized multilayer passive electric components, soft multilayer circuit, and cross-scale multimode sensors. The 3D laser printing method provides a versatile approach for developing chip-level soft electronics.

Transparent materials utilized as underwater optical windows are highly vulnerable to various forms of pollution or abrasion due to their intrinsic hydrophilic properties. This susceptibility is particularly pronounced in underwater environments where pollutants can impede the operation of these optical devices, significantly degrading or even compromising their optical properties. The glass catfish, known for its remarkable transparency in water, maintains surface cleanliness and clarity despite exposure to contaminants, impurities abrasion, and hydraulic pressure. Inspired by the glass catfish’s natural attributes, this study introduces a new solution named subaquatic abrasion-resistant and anti-fouling window (SAAW). Utilizing femtosecond laser ablation and electrodeposition, the SAAW is engineered by embedding fine metal bone structures into a transparent substrate and anti-fouling sliding layer, akin to the sturdy bones among catfish’s body. This approach significantly bolsters the window’s abrasion resistance and anti-fouling performance while maintaining high light transmittance. The sliding layer on the SAAW’s surface remarkably reduces the friction of various liquids, which is the reason that SAAW owns the great anti-fouling property. The SAAW demonstrates outstanding optical clarity even after enduring hundreds of sandpaper abrasions, attributing to the fine metal bone structures bearing all external forces and protecting the sliding layer of SAAW. Furthermore, it exhibits exceptional resistance to biological adhesion and underwater pressure. In a green algae environment, the window remains clean with minimal change in transmittance over one month. Moreover, it retains its wettability and anti-fouling properties when subjected to a depth of 30 m of underwater pressure for 30 d. Hence, the SAAW prepared by femtosecond laser ablation and electrodeposition presents a promising strategy for developing stable optical windows in liquid environments.

Liquid metal (LM) has potential applications in flexible electronics due to its high electrical conductivity and high flexibility. However, common methods of printing LM circuits on soft substrates lack controllability, precision, and the ability to repair a damaged circuit. In this paper, we propose a method that uses a magnetic field to guide a magnetic LM (MLM) droplet to print and repair a flexible LM circuit on a femtosecond (fs) laser-patterned silicone surface. After mixing magnetic iron (Fe) particles into LM, the movement of the resultant MLM droplet could be controlled by a magnetic field. A patterned structure composed of the untreated flat domain and the LM-repellent rough microstructure produced by fs laser ablation was prepared on the silicone substrate. As an MLM droplet was guided onto the designed pattern, a soft LM circuit with smooth, uniform, and high-precision LM lines was obtained. Interestingly, the MLM droplet could also be guided to repair the circuit broken LM lines, and the repaired circuit maintained its original electrical properties. A flexible tensile sensor was prepared based on the printed LM circuit, which detected the bending degree of a finger.