Ion Selective-OECTs for Blood Testing and In Vivo Sensing

Organic electrochemical transistors (OECTs) have received extensive attention owing to their ability to translate and amplify ion signals to electron signals recently. Compared to other types of transistors, in the operation of OECT, the ions from the electrolyte permeate into the channel and form a mixed of ionic-electronic conducting materials while a gate voltage (V<i>_g</i>) is applied. This phenomenon causes a volumetric change of the channel doping state, with significant modulations of source-drain current (I<i>_ds</i>) at low V<i>_g</i> (below 1V) and very high signal amplification (transconductance values can reach tens of mS). Furthermore, the promising biocompatibility allows the OECTs to be one of the most attractive candidates in biophysical and biochemical sensors for a large variety of targets. These sensors usually have high sensitivity and on-site amplification.<br/><br/>To date, there is a significant need for miniaturized ion sensors for monitoring of ion concentrations in health care applications. Portable and disposable ion sensors could monitor electrolyte levels in human blood or cerebral fluid, which can reflect the health conditions of the patients or neuron activities. In this talk, we will report an ion selective membrane-functionalized OECTs for specific ion detection. Compared to the OECT state-of-the-art, our sensor exhibits high performance, sensitivity of 126 μA/dec, response time of 1.9 s, dynamic range of 10^-4 to 1 M, excellent stability, reversibility and accuracy. Furthermore, calibrations for Na⁺ within the physiological range (110 mM – 160 mM) with blood serum show highly sensitivity of 498 μA/dec. While this investigation focused on Na+ as the target analyte, this platform can be adapted to sense variety of ionic species by simply tuning the ISM composition with the appropriate ionophore molecule. The advances in device architecture can further miniaturize devices and enable device placement in an implantable neural probe, while maintaining the ion sensing capability, i.e., a change of I<i>_ds</i> from 20 μA to 5 μA is observed when ion concentration changes from 1 mM to 100 mM. We expect the IS-OECT integrated neural probe to pave the way toward the design and fabrication of a new generation of multifunctional bioelectronics devices.