Blood ion testing is one of the methods that is commonly used for monitoring the immune status and providing physiological information for disease diagnosis. However, traditional blood ion sensing methods often require well-trained operators to process the whole blood sample and perform the measurements using bulky instruments, making real-time and continuous blood ion sensing at the bedside difficult. To address the above issues, we proposed a dual ion-selective membrane deposited ion-sensitive field-effect transistor (DISM-ISFET) sensor integrating a microchamber to enable on-chip serum extraction and in situ Na+/K+ ion sensing. As a proof of concept, we sequentially dispensed NaCl and KCl solutions at various concentrations on the DISM-ISFET to find out the highest ion sensitivity and selectivity. Next, we also confirm the high red blood cell sedimentation and serum purity using a microchamber. Finally, we evaluated the system performance using nine clinical whole blood samples and compared their Na+/K+ ion-sensing results with a commercial pocket ion meter. To sum up, our results showed that a DISM-ISFET system can successfully extract 200 μL serum from 500 μL whole blood sample and simultaneously achieve Na+/K+ ion sensing. All the sample processes and measurements can be finished within 10 min in a single chip. We envision this compact and easy-to-use system can be potentially used for various medical environments requiring real-time and continuous blood ion monitoring, such as in a hemodialysis room, operation room, and intensive care unit.
Keywords: blood ion sensing; ion-selective membrane (ISM); ion-sensitive field-effect transistor (ISFET); microfluidics; whole blood processing.