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. 2018 Feb 1;9(2):62. doi: 10.3390/mi9020062

Figure 1.

Figure 1

(a) Schematic structure and sensing mechanism of the film bulk acoustic resonator (FBAR) sensor coated with polyethyleneimine (PEI) nanofibers; (b) Photomicrograph of the fabricated device; (c) Block diagram of the testing system based on differential frequency processing; (d) Completed circuit board of the testing system.