Fig. 5.

Demonstration of a practical diagnosis application of the proposed portable COVID-19 sensor testing positive human sample (patient #6: saliva, 8000 copies/mL of B.1.1.7 variant) in real-time. Note that saliva samples were dissolved in 1% bovine serum albumin (BSA) in phosphate-buffered saline PBS) (1 × ), and 1 μL was dropped onto the sensor for the test. The sensor clearly distinguished variant positive sample and showed a signal-to-noise ratio of 67.57 dB and a response time of 0.6 s.