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The ever-increasing energy demand has highlighted the need for sustainable, low-carbon, and multi-functional energy solutions. Recently, multi-material additive manufacturing (MMAM) has become an emerging processing approach to prototype energy storage and conversion devices by enabling the fabrication of complex systems in a single, streamlined process while offering design freedom to customize end-product properties at precise, user-defined patterns and geometries. Moreover, it provides opportunities to fine-tune interfaces and material compositions at the microscale, opening new avenues for next-generation energy storage and conversion devices. As MMAM is still in its early stages, a comprehensive understanding of the interplay between material chemistry, processing methods, and device design is fundamental to fully realize its potential for developing high-performance energy materials. This review proposes a framework to bridge the gaps between the fundamental principles of processing physics and the practical implementation of various MMAM techniques in fabricating advanced energy storage and conversion devices, highlighting research challenges and future opportunities. 

Abstract In recent years, semiconductors, electronics, optics, and various other industries have seen a significant surge in the use of sapphire materials, driven by their exceptional mechanical and chemical properties. The machining of sapphire surfaces plays a crucial role in all these applications. However, due to sapphires’ exceptionally high hardness (Mohs hardness of 9, Vickers hardness of 2300) and brittleness, machining them often presents challenges such as microcracking and chipping of the workpiece, as well as significant tool wear, making sapphires difficult to cut. To enhance the machining efficiency and machined surface integrity, ultrasonic vibration-assisted (UV-A) machining of sapphire has already been studied, showing improved performance with lower cutting force, better surface finish, and extended tool life. Scribing tests using a single-diamond tool not only are an effective method to understand the material removal mechanism and deformation characteristics during such UV-A machining processes but also can be used as a potential process for separating IC chips from wafers. This paper presents a comprehensive study of the UV-A scribing process, aiming to develop an understanding of sapphire’s material removal mechanism under varying ultrasonic power levels and cutting tool geometries. In this experimental investigation, the effect of five different levels of ultrasonic power and three different cutting tool tip angles at various feeding depths on the scribe-induced features of the sapphire surface has been presented with a quantitative and qualitative comparison. The findings indicate that at feeding depths less than 6 μm, UV-A scribing with 40–80% ultrasonic power can reduce cutting force up to 50% and thus improve scribe quality. However, between feeding depths of 6 to 10 μm, this advantage of using ultrasonic vibration gradually diminishes. Additionally, UV-A scribing with a smaller tool tip angle (60°) was found to lower cutting force by 65% and improve scribe quality, effectively inhibiting residual stress formation and microcrack propagation. Furthermore, UV-A scribing also facilitated higher critical feeding depths at around 10 μm, compared to 6 μm in conventional scribing.