UG Summer Placement 2026 - University of Bath

Human hair is a biopolymer composed of two main regions: the cuticle and the cortex. The cortex contains helical intermediate filaments in which a crystalline phase is embedded within an amorphous matrix (1). The crystalline phase primarily consists of α-keratin. The cuticle provides mechanical protection to the cortex. In addition, strong disulfide crosslinks between adjacent keratin chains form a fibrous network that is highly resistant to chemical and biological degradation.

The presence of numerous hydrogen bonds within the α-keratin structure makes hair hygroscopic. Moisture uptake significantly influences both the mechanical and structural properties of hair fibres. The absorption and desorption of water are intrinsically linked to the fibrous architecture of hair, and understanding these processes is particularly important for the hair cosmetics industry (2). Previous research has shown that high-humidity environments affect mechanical properties such as Young’s modulus and flexibility (3). However, relatively few studies have investigated the combined mechanical and structural changes of hair fibres under controlled humidity conditions.

This project aims to systematically investigate how varying humidity levels influence both the mechanical properties and the microscopic structure of human hair fibres. Two different instrumentation techniques will be used for this project:

1. Dynamic mechanical analysis (DMA)- to measure how the flexibility of the hair fibres responds under varying humidity conditions. By gradually changing the relative humidity, the study measures how absorbed water softens the fibre and changes how it behaves over time under stress.
2. Small Angle X-Ray Scattering (SAXS)- to probe how keratin intermediate filaments, matrix proteins, and microfibrillar arrangements reorganise as humidity changes. In particular, it helps identify alterations in filament spacing, swelling behaviour, and structural ordering that occur as water molecules interact with the protein network.

By combining DMA and SAXS measurements, the project links humidity-driven nanoscale structural changes to changes in mechanical properties. This multi-scale approach improves understanding of how moisture affects biological fibrous materials and supports applications in cosmetics, textiles, and biomaterials. 

The key objectives are:

1. Develop experimental protocols using Dynamic Mechanical Analysis (DMA) to quantify changes in hair flexibility under controlled humidity conditions.
2. Establish Small-Angle X-ray Scattering (SAXS)-based methods to characterize structural alterations in hair fibres at different humidity levels.
3. Analyse and correlate the mechanical and structural data to identify the most effective testing approaches and underlying mechanisms.

References

1) Lima C.R.R.C., Lima R.J.S., Machado L.D.B. et al. Human hair: subtle change in the thioester groups dynamics observed by combining neutron scattering, X-ray diffraction and thermal analysis. Eur. Phys. J. Spec. Top. 229, 2825–2832 (2020).

2) Breakspear S., Evans T., Frueh P., Neu A., Noecker B., Popescu C. et al. The kinetics of moisture sorption by hair. Int. J. Cosmet. Sci. 47, 270–280 (2025).

3) Yang Y., Wen Y., Bin W., and Marc A. M. Structure and mechanical behaviour of human hair. Mater. Sc. and Eng: C, 73, 152-163 (2017).