The last decades many types of hydrogels have been developed. Hydrogels have the ability to swell or shrink as a function of physical and chemical variables, like temperature, pH or electric fields. This makes it possible to convert chemical energy directly into mechanical work. The aim of this research project is to develop a gastric CO2 sensor for diagnosing gastrointestinal ischemia, which means that the blood circulation of the stomach and intestines are poor resulting in high CO2 levels in the stomach. The principle is to clamp the material in a fixed volume and measure the change in pressure as a result of the stimuli.
Figure 1 shows a schematic representation of the sensor. The working is as follows: CO2 diffuses through the gas permeable membrane into the bicarbonate electrolyte starting a reaction which results in a pH change. The pH-sensitive hydrogel responds to this by generating a pressure which is measured by the pressure sensor. The advantage of this sensor is that no longer a reference electrode is needed, as in the classical Severinghaus CO2 electrode. Furthermore the sensor is very small so it fits easily in a catheter.
Figure 1. Exploded view and cross-section of the hydrogel-based CO2 sensor
Experiments have already shown that the sensor principle works successfully. The electrolyte and hydrogel are optimized to obtain maximal sensor signal. The next step is integrating the sensor in a catheter, which will be done in cooperation with Sentron Europe BV. After this clinical trials will be performed with the sensor at the local hospital (Medisch Spectrum Twente).
If you are interested and for instance would like to do your graduation work or practical term, please contact via the email address below.
Sebastiaan Herber and / or Wouter Olthuis
MESA+ Institute for Nanotechnology
University of Twente
P.O. Box 217
7500 AE Enschede