Low-Temperature Packaging of Ion-Sensitive Organic Field-Effect Transistors on Plastic for Multiple Ion Detection

In this work, a low temperature (<85°C) packaging approach is proposed to implement highly stable ion-sensitive organic field-effect transistors (ISOFET) for multiple ion detection. It is realized by flip-chip bonding organic field effect transistor (OFET) transducers and sensitive/reference electrodes (SE/RE) on a plastic carrier using silver paste as the conductive adhesive and subsequent sealing with silicone sealant. A hollow structure is adopted to prevent OFETs from damaging by residual solvents in the adhesive and also from the influence of moisture in the air. The packaged OFET maintains high stability during the packaging process and presents good shelf-life performance with excellent bias stressing stability even after 24 days. A flexible tag consisting of three ISOFETs is demonstrated to properly detect Na
⁺
, K
⁺
, and H
⁺
ions.