Fabrication and Characterization of a Wireless Bioresorbable Pressure Sensor

Embedding sensors into orthopedic devices can enable these implants to monitor the progress of the healing process or detect cues of complications. The simple structure of inductor-capacitor (LC) resonance sensors combined with their wireless readout offers a desirable basis for such sensors. A set of eight bioresorbable inductively coupled pressure sensors is fabricated. The conductors are formed by e-beam evaporation of magnesium (7 mu m) directly onto the substrates, after which two substrates are adhered to a holed spacer to form an LC sensor. All the sensors show a fairly linear pressure response in the physiological pressure range from 0 to 200 mm Hg with an average pressure sensitivity of -6.0 +/- 0.5 kHz mm Hg-1. After the pressure response tests, the effects of known error sources are determined. Finally, the sensor performance in vitro in buffer solution at +37 degrees C is evaluated. The sensors function tolerably for the first 8 h in immersion, after which they are disabled by mechanical changes in the sensor structure. To conclude, a bioresorbable battery-free wireless pressure sensor architecture with an adequate sensitivity for biomedical applications is described. However, further studies are required to improve the stability of the sensors under physiological conditions.