Quantifying tactile perception: Skin Tribology and Acoustic Emission

Kyriazis, Laure ORCID: 0009-0001-1619-540X (2025). Quantifying tactile perception: Skin Tribology and Acoustic Emission. University of Birmingham. Eng.D.

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Abstract

With the development of washing machines and detergent formulas, and the high temperatures and mechanical friction involved, as well as the poor quality of fast fashion textiles, fabric longevity is impacted. In this regard, it is important for manufacturers to innovate with better performing fabric softener compositions, whilst reducing the environmental impact of their formulations.

The aim of this thesis is to develop a methodology to quantify the tactile evaluation by consumers of treated substrates, in particular fabrics, and thus enhance the overall sensory properties provided by formulations.

The methodology developed in this work consists of the investigation of finger to fabric contacts, by quantifying finger friction with the means of a force plate apparatus, and the simultaneous measurement of the acoustic emission signal generated during the sliding contact. Acoustic emission corresponds to the high frequency stress waves generated within a material by a rapid release of energy, and can have multiple sources, including friction, fiber breakage, stick-slip or plastic deformation. The friction and acoustic methodologies were applied to several case studies, investigating the finger friction in sliding contact with untreated or treated substrates (including fabrics and non-planar substrates), and are linked
to the tactile assessment of the samples. The methodology was equally leveraged to study the stick-slip phenomena arising from the tactile assessment of the clean feel of planar glazed ceramic substrates treated with hand dishwashing formulations. Additionally, the deposition of softening actives is studied at the nanoscale to investigate the adsorption mechanism of cationic hydroxyethyl cellulose coacervates and their role in promoting reduction in the surface friction.

The method developed, and in particular the acoustic emission capability, was proven to be a successful tool to quantify the tactile benefits enhanced by consumer goods formulations, and in particular enhancing fabric softness from Fabric Care formulations and squeaky-clean feel from Dish Care formulas. Although we showed that higher surface hydrophobicity is obtained by higher total mass deposited during the wash cycle, further work is needed in order to fully understand the role of cationic hydroxyethyl cellulose in the deposition of full detergent formulations onto fabrics, in much simpler model systems before being transposed to full formulation compositions.

Type of Work:

Thesis (Doctorates > Eng.D.)

Award Type:

Doctorates > Eng.D.

Supervisor(s):