Microbalance Incorporated in Automatic Instrument for Mechanical Analysis of Human Hair Samples

Dia-Stron is a specialist company that builds automated instrumentation for the analysis of human hair and other fibres. Unilever recently approached the Company with a requirement to improve and automate the measurement of stiffness of human hair samples. Dia-Stron responded by designing and building a fully automated system that, once the sample cassette of up to 50 samples has been loaded, can analyse the fibres without further operator intervention.

Each sample is transported for analysis from the storage cassette to the measurement module by a single axis robotic arm. Once in the measurement module, the fibre is clamped at one end and then moved down so the free end applies a load to the force measurement device.

The bending moment of the hair can be determined by measuring the load applied and the distance moved by the clamped end of the fibre. Furthermore, because human hair has a cross-section that is more elliptical than round, the instrument is able to rotate each hair around its own axis for further measurements to be taken.

One key element in the success of the instrument is precise force measurement and for this Dia-Stron selected the Mk4 microbalance head from CI Electronics. This has an electronic control system that maintains the measurement position regardless of the load, which is vital for an application where force and displacement are being measured.