(Invited) Enzymatic Metal Oxide Electrolyte-Gated Field-Effect Transistors for Non-Invasive Glucose Biosensor

Abstract

Fabrication of nano-scaled biosensors with high sensing performance is essential demand for a future biological sensing system. Detection of biomolecules is conducted in terms of change in electrical properties of the biosensor so that the consideration of semiconductor material becomes more crucial. Although a lot of attractive attentions are attempted such as utilizing silicon nanowire or carbon nanotube, studies for investigating the highly reliable and biocompatible materials still have been progressed. Metal oxide material for biosensing application has an advantages of relatively high electrical characteristics and provides environmental condition for immobilizing an enzyme. InGaZnO (IGZO) has high electron mobility and reliability which leads a high sensitivity for detecting biomolecules. Adapting field effect transistor (FET) structure is additional approach to enhance the signal response of the sensor. The fundamental principle of the FET biosensor relies on its sensitive response to the variation of electric field or potential at the sensor surface resulting from the electrical interaction between the semiconductor and glucose molecules captured at the glucose oxidase (GOx). The FET biosensor also could be effectively integrated with other application circuits through conventional photolithography technologies. In addition, electrolyte-gated FET structure, utilizing an electrolyte as a gate insulator, shows a high sensitivity to the glucose concentration originated from a large capacitance of the electrolyte.IGZO based electrolyte-gated FET (IGZO-EGFET) biosensor is fabricated. The pH sensing is tested for predicting the biosensing performance of IGZO-EGFET. The pH sensitivity is measured as 52.5 mV/pH within 3 to 9 pH range, which is comparable to other nano material pH sensors. Immobilization of GOx on the IGZO surface is conducted via crosslinking modification with (3-aminopropyl)triethoxysilane (APTES) and glutaraldehyde treatment. Finally, the variation of glucose concentration is successfully identified on the GOx immobilized IGZO-EGFET. This study shows the IGZO-EGFET biosensor could lead to the applications of portable and real-time detecting sensor.