REVIEW 1800618 (1 of 16) © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.advmattechnol.de State-of-the-Art and Future Challenges of UV Curable Polymer-Based Smart Materials for Printing Technologies Cristian Mendes-Felipe, Juliana Oliveira, Ikerne Etxebarria, José Luis Vilas-Vilela, and Senentxu Lanceros-Mendez* DOI: 10.1002/admt.201800618 1. Introduction Over the past years, important efforts have been applied to expand the application of nanomaterials through the development of smart and multifunctional composites for their applications in areas ranging from micro devices, to sensor and actuators, as well as energy and biomedical applica- tions. [1–3] “Smart” materials are defined as a material in which one of its key proper- ties can be altered in a controlled manner in response to an external stimulus. [2–4] These stimulus-responsive materials can undergo, for example, variations in shape, mechanical properties, transparency, porosity, electrical or magnetic characteris- tics in response to thermal, mechanical or chemical external stimuli, among others. [1] One of the key implementation areas of smart materials are sensors and actua- tors, allowing to improve, monitoring, feedback, and safety, key issues of the Internet of Things and Industry 4.0 para- digms. [5] In this way, smart materials are an intense research area in which new materials, technologies, and applications will emerge in the near future. [2,3] Application areas of smart and multifunctional materials expand from consumer electronics, civil engineering, aerospace, and automobile to health care and wearables applications. [6,7] The potential application of smart materials would allow solving engineering problems with improved efficiency and provide an opportunity for the develop- ment of new solutions and products. [1,8] On the other hand, strategic and technological problems are still hindering the implementation potential of smart materials, despite their important advantages and specificities. [3,9] Namely, silicon-based smart materials are manufactured using the time-consuming, expensive, and complicated fabri- cation processes of traditional semiconductor devices. Further, those manufacturing methods are often based on subtractive processes. In contrast, several of the recently developed smart materials can be implemented by additive manufacturing (AM). [1,10] Additive manufacturing is rapidly expanding and modifying the way in which products are designed and manufactured. This technology allows to create complex geometries with cus- tomizable material properties, with design freedom and envi- ronmental advantage, [11] by transforming designed files into The one-step printing of fully functional electronic devices is one of the main goals of additive manufacturing. In general, this approach is increas- ingly growing, being one of the key developments additive manufacturing processes based on ultraviolet curing. The main reasons for this increasing interest in UV curing based technologies are its advantages, such as fast curing at room temperature, space and energy efficiency, high-resolution patterns, and solvent-free formulations. Despite the important developments, some challenges remain with respect to improving UV curing process and, in particular, to obtain smart UV curable materials, many times based on the inclusion of specific nanoparticles in a UV curable polymer matrix. Thus, this paper reviews the recent developments in UV curable smart materials for printing technologies focusing on both materials and processes. The curing mechanisms and the main materials used in UV photocurable resins are reviewed as well as the main smart and multifunctional materials obtained based on them. Finally, a summary of the main achievement and the future needs are indicated. This review represents therefore a landmark for the development of a new generation of UV curable smart and multifunctional materials and solutions. C. Mendes-Felipe, Dr. I. Etxebarria, Prof. J. L. Vilas-Vilela, Prof. S. Lanceros-Mendez BCMaterials—Basque Center for Materials Applications and Nanostructures UPV/EHU Science Park Leioa 48940, Spain E-mail: senentxu.lanceros@bcmaterials.net C. Mendes-Felipe, Prof. J. L. Vilas-Vilela Macromolecular Chemistry Group (LABQUIMAC) University of the Basque Country (UPV/EHU) Leioa 48940, Spain Dr. J. Oliveira, Prof. S. Lanceros-Mendez Center/Department of Physics University of Minho Braga 4710-057, Portugal Dr. J. Oliveira Algoritmi Research Centre University of Minho Guimarães 4800-058, Portugal Prof. S. Lanceros-Mendez IKERBASQUE Basque Foundation for Science Bilbao 48013, Spain The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/admt.201800618. Polymer-Based Inks Adv. Mater. Technol. 2019, 4, 1800618