Photothermal Lithography for Realizing a Stretchable Multilayer Electronic Circuit Using a Laser

Miniaturized Soft and Stretchable Multilayer Circuits through Laser-Defined High Aspect-Ratio Printing

Stretchable electronics enable seamless integration of wearables with the human body, thereby creating new opportunities in biomedical applications. Miniaturized multilayer stretchable printed circuit boards are key for achieving high functional density circuits with minimal footprint. However, current microfabrication technologies struggle with simultaneously achieving tissue-like softness (<<1 MPa), high resolution and low sheet resistance. This study demonstrates a scalable printing method that enables ultra-soft (<0.4 MPa) stretchable conductors (>300% strain) with high-resolution (<2.5 µm width) and high aspect-ratio tracks (>1) connected by ultra-fine (20 µm) vertical-interconnect-access (VIA) for multi-layered configurations. The method is based on stencil printing into laser-defined bio-masks comprising the abundant biopolymer lignin, thereby achieving printing capabilities beyond conventional methods in a sustainable manner. Based on the unique capabilities, a miniaturized multilayer ultra-soft wireless near-field-communication temperature logger is developed. Laser-defined printing can pave the way for the next generation of ultra-soft miniaturized wearables.

3D printing of thermochromic multilayer flexible film for multilevel information encryption

Flexible thermal-responsive encryption devices are widely employed in information encryption and anti-counterfeiting due to their cost-effectiveness and dynamic data encryption and decryption capabilities. However, most current devices are limited to a single layer of encryption, resulting in restricted decryption methods and storage capacity, as well as reliance on external heating. In this study, we integrate multiple layers of encryption within a single device and introduce self-heating thermochromic technology along with infrared thermal imaging encryption to establish a novel concept of a multilayer flexible encryption system. By combining infrared encryption and thermochromic encryption in three-dimensional space enhances the difficulty level for decryption while achieving high storage capacity for information. The internally integrated conductive heating layer within the multilayer structure facilitates rapid and adjustable heating for thermochromic patterns, eliminating the need for external heat sources. Furthermore, we employ a low-cost customizable multi-material integrated 3D printing process for manufacturing multilayer flexible encryption devices. This research presents an innovative solution for designing and fabricating high-density multilevel flexible encryption devices.

Light-Material Interactions Using Laser and Flash Sources for Energy Conversion and Storage Applications

This review provides a comprehensive overview of the progress in light-material interactions (LMIs), focusing on lasers and flash lights for energy conversion and storage applications. We discuss intricate LMI parameters such as light sources, interaction time, and fluence to elucidate their importance in material processing. In addition, this study covers various light-induced photothermal and photochemical processes ranging from melting, crystallization, and ablation to doping and synthesis, which are essential for developing energy materials and devices. Finally, we present extensive energy conversion and storage applications demonstrated by LMI technologies, including energy harvesters, sensors, capacitors, and batteries. Despite the several challenges associated with LMIs, such as complex mechanisms, and high-degrees of freedom, we believe that substantial contributions and potential for the commercialization of future energy systems can be achieved by advancing optical technologies through comprehensive academic research and multidisciplinary collaborations.

Direct Laser Writing: From Materials Synthesis and Conversion to Electronic Device Processing

Direct Laser Writing (DLW) has been increasingly selected as a microfabrication route for efficient, cost-effective, high-resolution material synthesis and conversion. Concurrently, lasers participate in the patterning and assembly of functional geometries in several fields of application, of which electronics stand out. In this review, recent advances and strategies based on DLW for electronics microfabrication are surveyed and outlined, based on laser material growth strategies. First, the main DLW parameters influencing material synthesis and transformation mechanisms are summarized, aimed at selective, tailored writing of conductive and semiconducting materials. Additive and transformative DLW processing mechanisms are discussed, to open space to explore several categories of materials directly synthesized or transformed for electronics microfabrication. These include metallic conductors, metal oxides, transition metal chalcogenides and carbides, laser-induced graphene, and their mixtures. By accessing a wide range of material types, DLW-based electronic applications are explored, including processing components, energy harvesting and storage, sensing, and bioelectronics. The expanded capability of lasers to participate in multiple fabrication steps at different implementation levels, from material engineering to device processing, indicates their future applicability to next-generation electronics, where more accessible, green microfabrication approaches integrate lasers as comprehensive tools.