Figure 1.

Probing tip–sample interaction forces at every tap. (a) Electron micrograph of an interferometric force sensor integrated to the end of a 280 µm long cantilever. The tip–coupled fingers were trimmed down by half the thickness for low force detection on soft cell samples. (b) Tip–sample interaction forces (F) of three consecutive taps acquired from tapping glass in liquid. The cantilever deflection (V) was phase–lagged to the forces but the calculated tip position (h) was in–phase to the forces. (c) The corresponding spectrogram of the forces shows the high frequency harmonics up to 15 times the drive frequency. (d) Reconstructed force–distance curves for tapping on glass and on a red blood cell.