2/26/2024 0 Comments 4d shapes![]() This is not conducive to the use of a single printing structure in multiple environments.Īnother pathway to achieve multiple stimuli-response 4D printing is to construct a bilayer structure by combining two materials with different response properties. When multiple stimuli are applied, the resulting responses are consistent. In essence, these stimuli-responses are ultimately attributed to one stimulation. In addition, the water-responsive material can also be used as the basis material, and then the response of another material can change the moisture ( Duigou et al., 2019), thereby controlling the change of the structure. The composites formed from a thermally responsive material and a material responsive to pH ( Hu et al., 2020 Lee et al., 2020) or cations ( Kirillova et al., 2017 Duigou et al., 2019) also have multiply stimuli responsiveness. Researchers added carbon nanotubes, ferroferric oxide or other fillers into the SMPs, LCEs or thermally responsive hydrogels to enable the material with the capability to convert electricity to heat ( Han et al., 2018 Liu et al., 2019), magnetism to heat ( Lin et al., 2019 Zhang et al., 2019b), or light to heat ( Cui et al., 2019 del Barrio and Sánchez-Somolinos, 2019), thereby realizing multi-responsive 4D printing. In such strategies, thermal is generally used as a basic stimulation. This draws on the existing multi-response composite method ( Hu et al., 2018 Li et al., 2018). By adding functional fillers to a certain type of smart material, the material has more responsiveness than the original one, which is one of the common strategies for achieving multi-response 4D printing. ![]() In the research field of 4D printing, multiple stimuli-response is of great significance for broadening the practical application of the printed structure in different environments ( Karis et al., 2017 Han et al., 2018). The shape-changing mechanism of 4D printing can be summarized as either using smart materials, such as hydrogels ( Champeau et al., 2020 Hu et al., 2020), shape memory polymers (SMP) ( González-Henríquez et al., 2019 Zhang et al., 2019c, d Kong et al., 2020), liquid crystal elastomers (LCE) ( Kotikian et al., 2018 Zhang et al., 2019a), etc., or creating mismatch strain within the printed object during the printing process by the combination of different responsive materials ( Tibbits, 2014) or the variation of printing process parameters ( van Manen et al., 2017), and then the deformation is generated in response to stimuli after printing. To date, most of the research on 4D printing involves the shape-shifting of 3D printed materials or structures. 4D printing has broad application prospects in many fields such as aerospace ( Akbari et al., 2018), drug delivery ( Ursan et al., 2013), biomedical equipment ( Gao et al., 2016 Yang et al., 2019), and flexible electronic devices ( Zarek et al., 2016), and has been attracting widespread attention. This research provides a universal multiple stimuli-responsive 4D printing method, which can effectively improve the intelligent responsiveness of 4D printing structures by combining multiple smart materials.ĤD printing refers to that the shape, property or functionality of 3D printed objects can change over time in response to external stimuli ( Kuang et al., 2019 Lui et al., 2019 Rastogi and Kandasubramanian, 2019 Shafranek et al., 2019), such as water, heat, light, electricity, etc. ![]() The diversified printing structure exhibits rich structural changes under one or both of the two stimuli of temperature and water. Based on the systematic study of the adapted printing parameters of the polyurethane elastomer, the effect of programmable variables on the deformation shape was investigated. Here we propose a 4D printing strategy with dual stimuli-responsive shape-shifting that responds to both temperature and water, by using a direct ink writing 3D printing method to deposit a polyurethane elastomer material with water-swelling characteristics on a heat-shrinkage shape memory polymer material to form a bilayer structure. The existing 4D printing technology is mostly limited to responsive to single stimulus, which means that the printing structure can only change under a pre-specified stimulus.
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