Computationally guided DIW technology to enable robust printing of inks with evolving rheological properties

Soft multifunctional materials allow for mechanical sensing or actuation as a response to multiple physical stimuli, while providing material stiffness that mimic soft biological tissues (≈1–10 kPa). One of the main bottlenecks in the state of the art relates to the difficulty for manufacturing complex shapes when using inks whose properties significantly change over the printing time. To overcome this issue, the implementation of a hybrid (theoretical-experimental) framework that allows optimal printability of time-dependent viscosity inks by using the direct ink writing technology. Although the rheological properties of the ink vary during printing time, a combination of theoretical and experimental methods provides evolving printing conditions that ensure efficient and robust printability over the process. The method removes the need of introducing additives to the ink. To enable this technology, an in-house printer that provides flexibility to modulate the extrusion pressure over printing time is developed. The method is validated by manufacturing magnetorheological elastomers and conductive soft materials for specific bioengineering and soft electronics applications.M.L.L.-D., G.d.A.-I., and S.G.-H. contributed equally to this work. The authors acknowledge support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 947723, project: 4D-BIOMAP). The authors acknowledge support from Programa de Apoyo a la Realizacion de Proyectos Interdiscisplinares de I+D para Jovenes Investigadores de la Universidad Carlos III de Madrid and Comunidad de Madrid (project: BIOMASKIN). DGG acknowledges support from the Talent Attraction grant (CM 2018 - 2018-T2/IND-9992) from the Comunidad de Madrid