Reducing Drift in Implantable Pressure Sensors

Pressure sensors are routinely used to monitor pressure in different regions of the body. These measurements are generally short-term as current sensors suffer from drift in accuracy, limiting practical use as a chronic implant. We report on the development of an implanted pressure reference for reducing sensor drift through recalibration, whilst the device is in situ. During a recalibration step, the mechanism generates a characteristic response into the pressure signal. The implanted sensor detects this response to perform on-board offset correction adjustments. Calibration is initiated with an external force, such as a simple finger pressing action. ANSYS modeling was used to adjust diaphragm dimensioning and deflection to induce a detectable correction signal. Testing was performed on a benchtop prototype with a ø10-mm titanium diaphragm. The accuracy of a recalibrated pressure sensor was ±0.15 mmHg. This is easily within the accuracy requirement for intracranial pressure monitoring of ±2 mmHg from the NS28 standard.