Flexible Conjugated Polymer Based Vertical Diode Temperature and Ammonia Gas Sensors for Medical Applications

Gastrointestinal ammonia levels and temperature can give indications on the health status of an individual. It is therefore of importance to develop sensors which can monitor these parameters. In this work, diode sensors with an organic semiconducting polymer, i.e., poly(3-hexylthiophene-2,5-diyl) (P3HT) sensing layer and Indium Tin Oxide (ITO) bottom and aluminum (Al) top electrode were fabricated. First, on rigid Indium Tin Oxide (ITO) -coated glass substrates and advancing to flexible ITO-covered polyethylene terephthalate (PET) to fabricate comfortable gastrointestinal sensors for future in vivo applications. Two deposition methods were evaluated for depositing of the Al electrode, namely thermal evaporation, or sputtering. When exposed to temperatures ranging from 36 to 41°C, the evaporated rigid diode sensor showed a noticeable current change down to 1°C temperature difference. Furthermore, polystyrene nanoparticles were used to create a nano-porous top electrode, to facilitate the diffusion of ammonia gas onto the P3HT sensing layer. These results pave the way to the fabrication of a conformable sensor which can be used in various application fields such as for gastrointestinal temperature and gas monitoring.