Mass-produced polyethylene-terephthalate film coated with tantalum pentoxide for pH measurement under ISFET detection configuration

This study reports an ISFET-based pH sensor utilizing a tantalum pentoxide (Ta₂O₅) as the sensing layer. Commercial PET film for mass production of touch panel coated with Ta₂O₅ film is used as the extended gate electrode connecting to a MOSFET chip for H⁺ ion measurement. The low-cost and plug-and-sense PET sensing file makes the developed sensor is disposable. The high corrosion-resistance of Ta₂O₅ layer greatly extends the lifetime and the pH sensing range for the solid-state sensor. Theoretical Nernst response is adopted to evaluate the sensing performance of the developed pH sensor. Results show that the developed pH sensor exhibits high sensitivity of 24.18 mV/pH and good linearity of R² = 0.9798 in the pH range from 1 to 13. In addition, the developed sensor also shows excellent sensing performance including ultra-fast response (<10 s), good repeatability (variation ~0.32 %) and good stability (variation <1 %). Moreover, the developed Ta₂O₅-based pH sensor shows low interference response to the existence of sodium and potassium interference ions. The developed solid state pH sensor provides a low-cost yet high performance way for developing disposable pH sensors.