Modified Clark Microsensors With Enhanced Sensing Current

Geometrical modification of three electrode Clark sensor is performed to enhance the sensing amperometric current. Two types of implantable microsensors are designed and characterized for measuring dissolved oxygen (DO
₂
). For type I sensor, the area of the reference electrode (RE) conventionally sandwiched between working electrode (WE) and counter electrode (CE), is optimized. In contrast to the conventional Clark sensors, the CE is sandwiched between WE and RE in type II sensor. Both type microsensors are fabricated using simple processes of silicon-based microfabrication technology. Electrochemical characterizations are performed on both sensors. For 96% DO
₂
, type I and type II microsensors demonstrate a sensing current of -0.87 μA and -2.35 μA as compared to a sensing current of -0.27 μA for the conventional Clark microsensor of same size. A sensitivity of 0.0094 μA/%DO
₂
and 0.024 μA/%DO
₂
are achieved with type I and type II microsensor, respectively in contrast to a sensitivity of 0.0027 μA/%DO
₂
of the conventional Clark microsensor of same size. The sensors show a lifetime of 48 hours. With its miniature size and enhanced sensing current the sensors have potentials for clinical and biomedical applications.