Near-Infrared Dual-Modal Sensing of Force and Temperature in Total Knee Replacement Using Mechanoluminescent Phosphor of Sr₃Sn₂O₇: Nd, Yb

Knee replacement surgery confronts challenges including patient dissatisfaction and the necessity for secondary procedures. A key requirement lies in dual-modal measurement of force and temperature of artificial joints during postoperative monitoring. Here, a novel non-toxic near-infrared (NIR) phosphor Sr₃Sn₂O₇:Nd, Yb, is designed to realize the dual-modal measurement. The strategy is to entail phonon-assisted upconversion luminescence (UCL) and trap-controlled mechanoluminescence (ML) in a single phosphor well within the NIR biological transmission window. The phosphor is embedded in medical bone cement forming a smart joint in total knee replacements illustrated as a proof-of-concept. The sensing device can be charged in vitro by a commercial X-ray source with a safe dose rate for ML, and excited by a low power 980 nm laser for UCL. It attains impressive force and temperature sensing capabilities, exhibiting a force resolution of 0.5% per 10 N, force detection threshold of 15 N, and a relative temperature sensitive of up to 1.3% K^-1 at 309 K. The stability against humidity and thermal shock together with the robustness of the device are attested. This work introduces a novel methodological paradigm, paving the way for innovative research to enhance the functionality of artificial tissues and joints in living organisms.