A batch fabricated capacitive pressure sensor with an integrated Guyton capsule for interstitial fluid pressure measurement

In this paper, we present the design, fabrication and test of a batch fabricated capacitive pressure sensor with an integrated Guyton capsule for interstitial fluid pressure measurement. The sensor is composed of 12 μm thick single crystalline silicon membrane and a 3 μm gap, hermetically sealed through silicon–glass anodic bonding. A novel batch scale method for creating electrical feed-throughs inside the sealed capacitor chamber is developed. The Guyton capsule consists of an array of 10 μm diameter access holes etched onto a silicon back-plate separated from the silicon sensing membrane by a gap of 5 μm. The presence of the Guyton capsule (i.e. plates with access holes plus the gap separating them from the sensing membrane) allows for the ingress of interstitial fluid inside the 5 μm gap following the implantation, thus, providing an accurate measurement of interstitial fluid pressure. The fabricated sensor is 3 × 2 × 0.42 mm3 in dimensions and has a maximum sensitivity of 10 fF mmHg−1. (Some figures in this article are in colour only in the electronic version)