The customized fabrication of soft active devices with self-healing function is demonstrated by 3D printing with vitrimeric thiol–acrylate photopolymers.

No abstract

Orthogonal photoreactions provide a unique way to locally and independently control (thermo)mechanical properties and functionality of polymer networks simply by choice of the wavelength. Herein, a library of acrylate functional coumarin monomers is synthesized, which are cured by sequence‐dependent wavelength orthogonality. In the presence of a long wavelength absorbing photoinitiator, the monomers undergo rapid curing by visible light induced radical chain growth polymerization. Subsequent irradiation with light in the UV‐A region selectively initiates the [2+2] photocycloaddition of the coumarin chromophores, which is confirmed by FTIR and UV–vis experiments. Through a well‐targeted design, acrylate‐based and thiol‐acrylate resin formulations are prepared, whose fast curing rate, low viscosity, and prolonged storage stability enable the one‐step fabrication of multi‐material structures by digital light processing (DLP) 3D printing. By using a dual‐wavelength printer, which operates at two different wavelengths (405 and 365 nm), objects comprising soft (ε = 22%, σ = 7.5 MPa) and stiff (ε = 2%, σ = 8.3 MPa) domains are printed with a single resin vat. Along with tensile properties, the wavelength selective change in the network structure features a local control of the glass transition temperature (ΔTg = 17 °C) in the 3D‐printed objects. Soft active devices are fabricated by dual‐wavelength DLP 3D printing, with distinct domains having a higher Tg and the local programming of multi shapes is demonstrated.

Inside Cover: In article 2200586, Sandra Schlögl and co‐workers demonstrate that Acrylate functional coumarin monomers are synthetized and cured by wavelength orthogonal photoreactions yielding soft (405 nm) and stiff (365 nm) networks. Advancing from thin films, the dual wavelength 3D printing of soft active devices is demonstrated with locally controlled mechanical and thermal properties using a single vat. The concept is highly versatile and applicable to acrylate and thiol‐acrylate photopolymers.