title: Nanometre-scale investigations by atomic force microscopy into the effect of different treatments on the surface structure of hair.
abstract: OBJECTIVE
  To investigate the effect of different washing regimes on the surface of human hair at the nanometre scale - comparable to the size of typical deposits left behind by commercial products.
  
  
  METHODS
  Atomic force microscopy (AFM) and related techniques.
  
  
  RESULTS
  It can be directly seen that washing hair using commercial hair care products removes deposits that naturally form on the shaft, revealing the underlying structure of the hair, whereas in many cases leaving new deposits behind. The spatial distribution of these deposits is explored and quantified. The spatial distribution of the surface charge of pristine hair is mapped, and the electrical screening effect of deposits is directly observed. We also show that the roughness of the treated hair depends directly on the type of product used, with a marked difference between shampoo and conditioner. Some products leave isolated deposits behind, whereas others leave layers of material behind which wet the hair surface.
  
  
  CONCLUSIONS
  Atomic force microscopy and the related techniques we have employed in a forensic approach is able to distinguish between different hair care products on the basis of the deposits they leave behind. This opens up the capability of further analysis tools to complement already existing techniques.
authors.affiliation: Nanoscience Centre, University of Cambridge, 11 JJ Thomson Avenue, Cambridge, CB3 0FF, UK; CambridgeNano, St. John's Innovation Centre, Cambridge, CB3 0WS, UK.
authors.forename: C
authors.initials: C
authors.lastname: Durkan
authors.forename: N
authors.initials: N
authors.lastname: Wang
mesh_terms: D006197:Hair / Q000648:ultrastructure*; D006203:Hair Preparations / Q000494:pharmacology*; D006801:Humans; D018625:Microscopy, Atomic Force
chemical_list: D006203:Hair Preparations
keywords: chemical analysis; hair treatment (washing, straightening, protection); polymers/surfactants