PH sensors are widely used in food processing, health monitoring, water quality monitoring, and many other fields. The pH sensor applied in the health monitoring field can realize the real-time measurement of human health information and timely prevent the occurrence of diseases by improving people's health levels. However, these sensors have some challenges in body fluid collection and temperature compensation. Here, we developed a pH sensor based on an extended-gate field-effect transistor (EGFET) with microfluidic channels and a temperature sensor to overcome these challenges. The sensor is prepared using a low-cost, solution-based process in which a temperature sensor is used for body temperature measurement and temperature compensation, and a microfluidic channel is used for body fluid collection. This pH sensor can measure both body temperature and pH of body fluid, where the temperature coefficient of resistance (TCR) of the temperature sensor is up to 5.17%, and the measurement result of body temperature is only 0.17 ℃ different from that of the gold standard. The pH sensitivity is 58.41 mV pH−1, and the pH value is only 0.066 deviating from the standard pH value. The sensor is expected to be used on a large scale in the applications of wearable health monitoring.
Owing to the separation of field-effect transistor (FET) devices from sensing environments, extended-gate FET (EGFET) biosensor features high stability and low cost. Herein, a highly sensitive EGFET biosensor based on a GaN micropillar array and polycrystalline layer (GMP) was fabricated, which was prepared by using simple one-step low-temperature MOCVD growth. In order to improve the sensitivity and detection limit of EGFET biosensor, the surface area and the electrical conductivity of extended-gate electrode can be increased by the micropillar array and the polycrystalline layer, respectively. The designed GMP-EGFET biosensor was modified with l-cysteine and applied for Hg2+ detection with a low limit of detection (LOD) of 1 ng/L, a high sensitivity of −16.3 mV/lg(μg/L) and a wide linear range (1 ng/L-24.5 μg/L). In addition, the detection of Hg2+ in human urine was realized with an LOD of 10 ng/L, which was more than 30 times lower than that of reported sensors. To our knowledge, it is the first time that GMP was used as extended-gate of EGFET biosensor.
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