Self-recoverable Ca5Ga6O14:Eu³⁺-ZnS:Cu mechanoluminescent composite for visualized stress and temperature sensing

Mechanoluminescent (ML) materials hold significant potential for applications in visual stress and temperature sensing. However, most studied ML materials are largely limited to trap-controlled types, which necessitate prior optical excitation for activation and require continuous optical stimulation to maintain luminescent intensity. This dependency significantly restricts their performance in practical applications. In this study, we developed self-recoverable CGO:Eu³⁺ red-emitting ML powders and combined them with green-emitting ZnS:Cu ML powders in polydimethylsiloxane (PDMS) to facilitate visualized stress and temperature sensing. The ML intensity of CGO:Eu³⁺ and ZnS:Cu demonstrates distinct trends at varying strains; thus, the CGO:Eu³⁺-ZnS:Cu composite elastomer with a CGO:Eu³⁺ to ZnS:Cu ratio (CtZ ratio) of 4:1 exhibits the most significant ML color change in response to strain variations. Additionally, the notable difference in thermal quenching performance between CGO:Eu³⁺ and ZnS:Cu powders enables the composite elastomer with a CtZ ratio of 2:1 to differentiate temperature based on changes in ML color, achieving a maximum relative sensitivity ( S r) of 2.2 % K⁻¹ at 200 °C. The composite elastomers produced exhibited ML color changes that are easily perceptible to the human eye in response to varying stress and temperature conditions, thereby making them suitable for applications in intelligent gesture recognition and temperature detection.