Low-firing thick-film piezoresistive sensors for medical instruments

In this work, a low-firing thick-film materials system allowing fabrication of piezoresistive sensors on surgical alloys is presented in detail, with application to a force-sensing surgical instrument. The system comprises a series of individual thick-film dielectric, conductor, resistive and overglaze compositions based on a lead borosilicate glass matrix. The moderate achieved firing temperature, around 625°C, greatly increases compatibility with metallic substrates, allowing the use of high-strength medical alloys with low thermal degradation. Specific fillers for the dielectric layers increase adhesion on steel substrates and allow thermal matching to austenitic and ferritic / martensitic steels, as well as titanium alloys. The functionality of this materials system is successfully demonstrated here by implementing it into a previously developed ligament-balancing force sensor for total knee arthroplasty (TKA) [1]. Keywords: Medical operations; total knee arthroplasty; thick-film force sensors; medical alloy