A Nanometer Resolution Wearable Wireless Medical Device for Non Invasive Intracranial Pressure Monitoring

The non-invasive intracranial pressure (NIICP) method based on a skull deformation has been proven to be a significant tool for an assessment of the intracranial pressure (ICP) and compliance. Herein, we present the development and characterization of a novel wireless sensor that uses this method as its working principle and was designed to be easy to use, to have a high resolution, and to achieve a good accessibility. Initially, a brief review of the physiology fundamentals of the ICP and the historic evolution of the NIICP method are mentioned. The sensor architecture and the rationale for the chosen components are then presented, aiming to ensure nanometer displacement measurements, the conversion of analog resolution to digital at a high speed, the fewest amount of distortion, wireless communication, and signal calibration. The NIICP signal has a typical amplitude of $5~\mu \text{m}$ , and thus a resolution of at least 1% of this amplitude is required for an NIICP waveform analysis. We also demonstrate a 40-nm resolution of the sensor using a nanometric displacement test system that can also respond dynamically for NIICP signals from 50 to 180 bpm without any significant distortion (maximum deviation of P2/P1 ratio of 2.6%). The future applications for this device are broad and can enhance a clinical assessment of the intracranial dynamics.