Broadband Rheological Characterisation of Soft Functional Materials

Conventional bulk rheology presents a well-established technique for the mechanical characterisation of soft materials, ranging from liquid suspensions and emulsions to tenuous or even stiff gels. Probing the internal microstructure and understanding the relaxation of such materials has always been of great interest to industries, where the flow behaviour and stress response are of paramount importance in quality control for achieving high product performance. However, although generally reliable, bulk rheology suffers from certain limitations related to the frequency range and measurement sensitivity, which do not allow probing fast processes occurring on the microscale in complex viscoelastic fluids. This has sparked the search for an alternative method of extracting the high-frequency response and has led to a significant rise in the use of microrheology, where tracer particles provide indirect information about the viscoelasticity of the fluid, in which they are embedded. Recent advances in the fields of optics and electronics paved the way for using laser trapping and light scattering beyond their standard applications. In this thesis, I combine mechanical and optical measurements applied on newly emerging materials in order to extract their viscoelasticity over a broad frequency range in an attempt to gain better understanding of their internal self-organisation. In particular, I concentrate on DNA-based and clay-based hydrogels, which exhibit strong degree of swelling when dispersed in an aqueous solvent. These soft transient networks represent intriguing thermoresponsive and time-dependent systems, where the flexibility in the design opens up new exciting avenues within the field of nanotechnology.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2021

Author dc:creator

• Stoev, Iliya

Advisor dc:contributor.advisor

• Eiser, Erika

• microrheology
• viscoelasticity
• optical tweezers
• dynamic light scattering
• complex fluids
• hydrogels
• DNA nanotechnology

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/0c2b8fb0-481b-4136-8d3a-24bdf92c2211/download
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.58218

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/311129