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. 2018 Sep 4;13(9):e0202833. doi: 10.1371/journal.pone.0202833

Fig 1. Principle of AFM-IR.

Fig 1

(A) The sample surface is illuminated with a tunable IR laser. When the wavelength of the laser corresponds to an IR absorption band of the sample, the IR absorption will create heat and entail a rapid thermal expansion of the absorbing regions. This rapid thermal expansion induces oscillations (B) in the AFM tip at its resonant frequencies (C). Because the absorption is proportional to the cantilever oscillation, an absorption spectrum can be derived. (D) Absorption spectrum acquired on cancellous bone in which the phosphate band (920–1200 cm-1) and the amide I band (1592–1712 cm-1) characterize the mineral and collagen components, respectively. Adapted with permission from Anasys Instruments.