Indium tin oxide coated PET for differential pH-sensing using field-effect transistor based sensor

• Published in: Micro & nano letters Vol. 13; no. 11; pp. 1525 - 1530
• Main Authors: Mokhtarifar, Naser, Goldschmidtboeing, Frank, Woias, Peter
• Format: Journal Article
• Language: English
• Published: Stevenage The Institution of Engineering and Technology 01.11.2018; John Wiley & Sons, Inc
• Subjects: amplifiers; buffer solution; Buffer solutions; chemical sensors; Circuits; Cleanrooms; Coating effects; commercial ITO‐PET sheet; constant‐charge amplifier circuitry; differential pH‐sensing; EGFET pH‐sensor; electrode shape; Electrodes; extended gate field‐effect transistor pH‐sensor; Field effect transistors; field‐effect transistor based sensor; gate‐terminal; high drift signal rate; indium compounds; indium tin oxide coated PET; Indium tin oxides; InSnO; laser beam machining; Laser machining; laser micromachining quality; Linearity; low‐cost EGFET‐based pH‐sensor; measurement cell; metal–oxide–semiconductor field‐effect transistor; Micromachining; MOSFET; MOSFETs; moulded ITO‐PET electrode; noise level; pH measurement; pH‐sensitivity; Polyethylene terephthalate; polyethylene terephthalate substrate; polymer films; pseudoreference electrode; reference electrode; Semiconductor devices; Sensitivity; sensor signal; Sensors; sheet materials; Special Section: Selected Papers from The 13th Annual IEEE International Conference on Nano/Micro Engineered and Molecular Systems (IEEE-NEMS 2018); Substrates; tin compounds; Transistors; micromachining; MOSFET; laser micromachining quality; metal–oxide–semiconductor field-effect transistor; indium compounds; low-cost EGFET-based pH-sensor; pH-measurement; indium tin oxide coated PET; EGFET pH-sensor; constant-charge amplifier circuitry; measurement cell; noise level; reference electrode; buffer solution; field-effect transistor based sensor; tin compounds; differential pH-sensing; laser beam machining; high drift signal rate; polymer films; pseudoreference electrode; pH-sensitivity; polyethylene terephthalate substrate; chemical sensors; sensor signal; sheet materials; commercial ITO-PET sheet; moulded ITO-PET electrode; extended gate field-effect transistor pH-sensor; amplifiers; InSnO; pH measurement; electrode shape; gate-terminal
• ISSN: 1750-0443; 1750-0443
• DOI: 10.1049/mnl.2018.5240

Indium tin oxide (ITO) on polyethylene terephthalate (PET) substrate is characterised in terms of pH-sensitivity. Commercial ITO/PET sheet was cut in a shape of electrode and was connected to the gate-terminal of a metal–oxide–semiconductor field-effect transistor as the sensory part, creating an extended gate field-effect transistor (EGFET) pH-sensor. The quality of laser micromachining as well as the moulded ITO/PET electrode is investigated. The pH-sensitivity and linearity of the sensor signal are studied over time for a single hanging ITO/PET electrode. With the help of a constant-charge amplifier circuitry, the reference electrode, dipped in the measurement cell, is grounded. Therefore, the noise level, coupled into the sensor signal from environment, is decreased and also integration of the second sensor to the measurement cell becomes possible. The pH-measurement is carried out while EGFET pair, immersed into a buffer solution next to a pseudo-reference electrode, is working in differential mode to compensate for the high drift signal rate which is common for this type of sensors. As the result, a very low-cost EGFET-based pH-sensor is achieved based on commercially available products independent of costly cleanroom processes.