IR super-resolution imaging of avian feather keratins detected by using vibrational sum-frequency generation

IR super-resolution imaging of the cross section of the rachis of an avian feather was carried out by using a vibrational sum-frequency generation (VSFG) detected IR microscope with a sub-micrometer spatial resolution. In the YYX polarization combination, we clearly observed strong signals in the entire region of the rachis at the amide I vibration of β-keratin. On the other hand, the signal disappears from most of the cross section in the XXY polarization combination. Because the VSFG imaging detects the signal only from the interface, we conclude that the interfacial deflection inside of a rachis was detected. [Display omitted] •IR super-resolution imaging of avian feather keratins detected by using vibrational sum-frequency generation.•The polarization dependence of the amide I vibration of β-keratin was measured.•The VSFG signal of this method was generated from the interface inside the sample.•The β-keratin at the interface inside the sample is aligned with the long axis of the cross section of the rachis.