Direct ink writing of aerogels: Fundamentals, strategies, applications, and perspectives

Aerogels, which can be made from virtually any material, are exceptional examples of multifunctional materials. They hold great promise for interdisciplinary science across physics, chemistry, and biology, etc. However, their inherently fragile structure poses significant challenges to traditional manufacturing processes. Additive manufacturing—commonly known as 3D printing—has emerged as a novel approach for shaping aerogels, among which great attention has been paid to the Direct Ink Writing (DIW) technology for its convenience, versatility and accessibility. Unfortunately, the universal application of DIW technology in aerogel shaping remains a challenge, largely due to the absence of specialized rheological designs and advanced DIW strategies. Consequently, this review primarily focuses on the rheological behavior of aerogel-based inks to elucidate the fundamentals of aerogel DIW. Next, this review presents some advanced DIW strategies from the ink toolkit expansion, printing process modification to ingenious posttreatment. Also, the impressive applications of aerogel DIW are introduced. Lastly, a comprehensive view of the development of aerogel DIW is concluded and proposed. The review summarizes the fundamental theory, recent progresses and challenges on aerogel DIW, aiming to provide the state-of-the-art concept and theoretical guidance for the next generation of aerogel DIW.