“…We assume the frequencies of the first mode (in-phase mode) is ω 1 , and the second mode (out-of-phase mode) is ω 2 . So, in particular, when ǫ = 0, F 1 = F , the rest of the driving force is equal to zero, and ω in (9) equals the resonant frequency ω 1 , which is the resonant frequency of the first mode for mode-localised sensors [25]. Thus, we can attain AR, sensitivity and the resolution limit of 2, 3 and 4-DoF resonant systems.…”