In-mold electronics (IME) is attracting increasing attention in several industrial sectors, including automotive, medical, consumer electronics, and aerospace, due to the present demands on enhancing human–machine interactions. To achieve the new technological paradigm, devices must adopt more ergonomic and attractive shapes, in particular, 3D geometries. In this context, this work presents novel electroluminescent (EL) inks to be integrated into alternate-current EL (ACEL) devices able to be printed and thermoformed into a 3D shape and provide efficient lighting. The EL inks are based on styrene-ethylene-butylene-styrene (SEBS) and polyvinyl alcohol (PVA) polymers, each of them incorporating 60% wt. of copper-doped zinc sulfide (ZnS:Cu) microparticles. The composites display a compact morphology characterized by a uniform distribution of ZnS:Cu particles. They exhibit thermal properties suitable for thermoforming, chemical stability, and favorable mechanical properties at room temperature, with a Young's modulus of 5.7 MPa at 180 % elongation at break for SEBS and 2039 MPa at 1.8 % elongation at break for PVA. Additionally, the composites possess excellent dielectric properties, with dielectric constants of 6 and 90 at 1 kHz for SEBS and PVA, respectively. The ink’s viscosities are in the range of 400–800 mPa·s for PVA/ZnS:Cu and 350–400 mPa·s for SEBS/ZnS:Cu. Thermoformed PVA-based ACEL devices exhibited luminance reductions of 18 %, 25 %, and 26 % under deformations of 6 %, 15 %, and 40 %, respectively, and thermoformed SEBS-based ACEL devices demonstrated luminance decreases of 15 % under 6 % deformation, and 22 % under both 15 % and 40 % deformation. The study demonstrates that the developed inks are suitable for their intended application, and the devices remain functional under significant deformation levels. These findings underscore a cost-effective and straightforward path for fabricating lighting solutions that are compatible with integration into printed electronic circuits and in-mold electronics (IME) processing. Electroluminescent composites based on styrene-ethylene-butylene-styrene (SEBS) and polyvinyl alcohol (PVA) polymers incorporating copper-doped zinc sulfide (ZnS:Cu) particles are able to be printed and thermoformed into a 3D shape providing efficient lighting, allowing the development of novel alternate-current electroluminescent (ACEL) devices with capability of emitting light after a thermoforming process under different deformation percentages. Highlights 85 cara • Electroluminescent (EL) composite inks based on SEBS and polyvinyl alcohol PVA were developed. • The developed inks are suitable for printing process, and the devices remain functional under significant deformation levels. • Both composites were successfully thermoformed inducing 6, 15, and 40 % strain. • The EL composites show capability of emitting light after a thermoforming process.
Polícia et al. (Mon,) studied this question.