Periprosthetic joint infection (PJI) following total hip or knee arthroplasty occurs in 1 to 2% of primary procedures, often requiring multi-stage revision surgeries and extended antibiotic regimens. Bacterial metabolism shifts local synovial fluid pH from physiological 7.4 down to acidic 6.2. This paper details micro-fabricated passive resonant pH sensors embedded into ultra-high-molecular-weight polyethylene (UHMWPE) acetabular liners.
pH-responsive hydrogels expand in acidic environments, mechanically altering the gap of an embedded capacitor and shifting the resonant frequency of an integrated copper coil by up to 1.4 MHz per pH unit.
Bench testing under cyclic mechanical loads of 3,000 Newtons confirmed sensor durability exceeding 10 million cycles, successfully identifying Staphylococcus epidermidis biofilm formation within 48 hours of inoculation.