Nanomechanical measurements of hair as an example of micro-fibre analysis using atomic force microscopy nanoindentation

The characterisation of nanoscale surface properties of textile and hair fibres is key to developing new effective laundry and hair care products. Here, we develop nanomechanical methods to characterise fibres using an atomic force microscope (AFM) to give their nanoscale modulus. Good mounting methods for the fibre that are chemically inert, clean and give strong mechanical coupling to a substrate are important and here we detail two methods to do this. We show, for elastic nanoindentation measurements, the situation when the tip radius significantly affects the result via a function of the ratio of the radii of the tip and fibre and indicate the importance of using an AFM for such work. A valid method to measure the nanoscale modulus of fibres using AFM is thus detailed and exampled on hair to show that bleaching changes the nanoscale reduced modulus at the outer surface.

► Valid AFM nanomechanical characterisation of fibres developed.
► Good mounting methods detailed.
► Errors of not taking the fibre radius into account in indentation theory highlighted.
► Modulus of bleached and unbleached hair compared.