Roll-to-Roll Nanoforming of Metals Using Laser-Induced Superplasticity

Laser-Based Selective Material Processing for Next-Generation Additive Manufacturing

The connection between laser-based material processing and additive manufacturing is quite deeply rooted. In fact, the spark that started the field of additive manufacturing is the idea that two intersecting laser beams can selectively solidify a vat of resin. Ever since, laser has been accompanying the field of additive manufacturing, with its repertoire expanded from processing only photopolymer resin to virtually any material, allowing liberating customizability. As a result, additive manufacturing is expected to take an even more prominent role in the global supply chain in years to come. Herein, an overview of laser-based selective material processing is presented from various aspects: the physics of laser-material interactions, the materials currently used in additive manufacturing processes, the system configurations that enable laser-based additive manufacturing, and various functional applications of next-generation additive manufacturing. Additionally, current challenges and prospects of laser-based additive manufacturing are discussed.

Electrochemically-driven actuators: from materials to mechanisms and from performance to applications

Soft actuators, pivotal for converting external energy into mechanical motion, have become increasingly vital in a wide range of applications, from the subtle engineering of soft robotics to the demanding environments of aerospace exploration. Among these, electrochemically-driven actuators (EC actuators), are particularly distinguished by their operation through ion diffusion or intercalation-induced volume changes. These actuators feature notable advantages, including precise deformation control under electrical stimuli, freedom from Carnot efficiency limitations, and the ability to maintain their actuated state with minimal energy use, akin to the latching state in skeletal muscles. This review extensively examines EC actuators, emphasizing their classification based on diverse material types, driving mechanisms, actuator configurations, and potential applications. It aims to illuminate the complicated driving mechanisms of different categories, uncover their underlying connections, and reveal the interdependencies among materials, mechanisms, and performances. We conduct an in-depth analysis of both conventional and emerging EC actuator materials, casting a forward-looking lens on their trajectories and pinpointing areas ready for innovation and performance enhancement strategies. We also navigate through the challenges and opportunities within the field, including optimizing current materials, exploring new materials, and scaling up production processes. Overall, this review aims to provide a scientifically robust narrative that captures the current state of EC actuators and sets a trajectory for future innovation in this rapidly advancing field.

Roll-to-plate 0.1-second shear-rolling process at elevated temperature for highly aligned nanopatterns

The shear-rolling process is a promising directed self-assembly method that can produce high-quality sub-10 nm block copolymer line-space patterns cost-effectively and straightforwardly over a large area. This study presents a high temperature (280 °C) and rapid (~0.1 s) shear-rolling process that can achieve a high degree of orientation in a single process while effectively preventing film delamination, that can be applied to large-area continuous processes. By minimizing adhesion, normal forces, and ultimate shear strain of the polydimethylsiloxane pad, shearing was successfully performed without peeling up to 280 °C at which the chain mobility significantly increases. This method can be utilized for various high-χ block copolymers and surface neutralization processes. It enables the creation of block copolymer patterns with a half-pitch as small as 8 nm in a unidirectional way. Moreover, the 0.1-second rapid shear-rolling was successfully performed on long, 3-inch width polyimide flexible films to validate its potential for the roll-to-roll process.

Temperature-affected nano-deformation behavior of nanometals in ultrahigh-strain-rate formation processes

As metal forming processes move toward high speed, high throughput, high precision and small scale with temperature dependence, clarifying the fundamental nano-deformation behavior of metals is critical for the optimization of manufacturing processes, and the control of nano-optical, electrical, mechanical or surface properties. Unfortunately, limited by the time scale and sample size, the effect of temperature on the deformation behavior of nano-metals during the ultrahigh-strain-rate forming process remains largely unexplored. This study demonstrates the nonlinear effect of temperature on the formability of nano-metals for the first time. Temperatures below 673 K facilitated the formability of nano-metals benefiting from the temperature-promoted dislocation proliferation process, whereas temperatures above 673 K weakened the plasticity of the nano-metal due to the activation of phase transformation. Frequent phase transition activation and accelerated dislocation annihilation at high temperatures reduced interstitial transport channels and delayed atomic transfer. Based on the temperature response of nano-metals in deformation mechanisms, defect evolution behavior and formability, the constitutive model and nano-deformation mechanism map of nano-metals in ultrahigh-strain-rate forming processes are proposed. The objective of this work is to provide basic support for the reasonable matching of nano-forming technology and processing temperature, and the determination of the optimal process window through fundamental nano-deformation behavior exploration.

Analyses of pattern quality in roll-to-roll digital maskless lithography with positional errors

In roll-to-roll digital maskless lithography (R2R DML) equipment, it is difficult to achieve high quality, owing to surface deformation that affects the pattern position. To address this issue, we simulated the patterning results of R2R DML to analyze the relationship between positional errors and pattern quality. Errors perpendicular to the pattern direction exhibited a 1.3-2 times greater effect on the linewidth and line edge roughness compared to those parallel to this direction. We confirmed that positioning errors could lead to defects in which the photoresists were not fully exposed. Finally, through simulations, we found that the effect of positional errors could be reduced by controlling the array spot separation length.

A Review on Micro/Nanoforming to Fabricate 3D Metallic Structures

With the rapid development of micro-electromechanical systems (MEMS), micro/nanoscale fabrication of 3D metallic structures with complex structures and multifunctions is becoming more and more important due to the recent trend of product miniaturization. As a promising micromanufacturing approach based on plastic deformation, micro/nanoforming shows the attractive advantages of high productivity, low cost, near-net-shape, and excellent mechanical properties, compared with other non-silicon-based micromanufacturing technologies. However, micro/nanoforming is far less established due to the so-called size effects in terms of materials models, process laws, tooling design, etc. The understanding of basic issues on micro/nanoforming is not yet mature, and it is currently a topic of rigorous investigation. Here, a systematic review on the micro/nanoforming processes of 3D structures with multifunctional properties is presented, wherein also a critical examination of the interplay between relevant length scales and size effects affecting the structural integrity of micro/mesoscale metallic systems is also provided. Finally, the challenges of micro/nanoscale fabrication are proposed, including the development trends of new micro/nanoforming processes, multiple field coupling effects, and theoretical modeling at the trans-scale.