FridayAFM - Animal hair fibers

Héctor here, your AFM expert at Nanosurf calling out for people to share their Friday afternoon experiments. Today I show you the difference between mouse and horse hair.

Can we easily distinguish an hair fiber from a mouse of that one from a horse (a horse tail in this case)?

Distinguishing the origin of hair fibers can have massive importance, for instance, in forensic analysis (See Ref 1), or in quality control (not going to advertise a company in particular, simply look for "fiber identification lab") . However, how difficult it is? This week I got very lucky and found pre-prepared samples for optical microscope that include animal hair fibers. So, I decided to image them and show you how they look. I also happen to have a violin bow around, which is made of horse hair, so... I added it to the list.

1 Animal hair fibers sources.

The tricky parts of imaging these fibers are fixing them, and water/contaminants (I have no idea how they were handled). Luckily, imaging in static mode solves these two problems, you just need to scan several times until residues are cleaned from the surface by the AFM probe.

1 3D rendering of topography. AFM images taken using Multi-75 probes in static mode.

As you can see, mouse and hare look very similar, not sure I will be able to distinguish between them, but dog for instance (no idea the breed), seems quite different, with broken edges, less defined. Also, mouse and hare have a texture on top, stripes (which seems to correspond to new cuticle surface, see Ref 2).

1 3D rendering of topography. AFM images taken using Multi-75 probes in static mode.

Horse and sheep are also somehow similar, although sheep cuticles seem to be larger, more distance between steps. Both of them with quite broken edges. My classification will be that mouse/horse are easy to distinguish, same mouse and dog, or mouse and sheep, but mouse and hare are very similar. Similarly, dog/horse, hare/horse are easy, but sheep/horse are more difficult to differentiate.

Let's recap. We imaged several different hair fibers from different animals, showing the differences and the similarities. This Highlights the importance of databases for both forensic and quality control.  

I hope you find this useful, entertaining, and try it yourselves. Please let me know if you use some of this, and as usual, if you have suggestions or requests, don't hesitate to contact me.