Calcium ions detection using miniaturized InN-based sensor

The packaging and integration of calcium ion (Ca²⁺) ISFET sensor chips is a challenge to sensor technology and materials. This study used ultrathin InN ion sensitive sensor (~10 nm) with gate region functionalized with phosphotyrosine (p-Tyr) to detect calcium ion (Ca²⁺) in aqueous solution. The miniaturized InN sensor provides to integrate with existing medical equipment for real-time and continuous monitoring of human blood, the sensor was miniaturized to 100 μm by 400 μm and integrated at the tip of hypodermic injection needle (18G). The sensor has current variation ratio of 1.11% with per decade change of Ca²⁺ and a detection limit of 10^-6 M. The response time is 5 seconds.