An extended-gate CMOS sensor array with enzyme-immobilized microbeads for redox-potential glucose detection

An extended-gate CMOS sensor array with enzyme-immobilized microbeads for redox-potential glucose detection is demonstrated for the first time. Redox-potential detection has the possibility to achieve high accuracy because it is not affected by the buffer conditions. Despite this high-accuracy property, redox-potential detection requires a sufficient amount of enzyme, which leads to increased cost. In order to reduce the enzyme consumption while maintaining the detection capability, we have introduced enzyme-immobilized microbeads. By using the microbeads, the enzyme can be efficiently positioned and reused several times. Thus, the required amount of enzyme can be reduced dramatically. To verify the proposed concept, we have developed and measured a prototype with a 0.6-μm CMOS test chip including the microfluidics. Measurements successfully demonstrate glucose detection with a sensitivity of -61.6 mV/decade while reusing identical enzyme-immobilized microbeads.