Scalable soft matter patterning from the macro to the nanoscale
File(s)
Author(s)
Nania, Manuela
Type
Thesis
Abstract
Surface patterning is important for a range of engineering applications, including
controlled wetting and spreading of liquids, adhesion and assembly of smart
coatings. There is therefore a need of simple, cost-effective and scalable techniques
for pattern formation over a wide range of scales. Conventional methods
fail to comply with these requirements, as costs and complexity increase in the
attempt to impress nm to µm scale features. By contrast, wrinkling of bi-(multi-
)layers is inherently inexpensive, scalable and robust, and has the potential for soft
matter patterning from the nano- to the macro-scale. This work investigates the
controlled multi-layer generation of polydimethylsiloxane (PDMS) glassy skins via
surface oxidation using plasma exposure and/or ultraviolet ozonolysis (UVO). Uniaxial
mechanical compression is then employed to induce pattern formation via a
well-known wrinkling instability. Topographies with wavelengths down to 45 nm
are achieved, for the first time, as well as features with characteristic lengthscales
of ∼ 10s µm. Moreover, simple design routes for double frequency nested pattern
formation, imposed by compression of tri-layer laminate films, are established.
The work concludes by exploiting wrinkling as a method for the mechanical characterisation
of thin drying films. A time-resolved wrinkling interrogation during
film drying is established as a simple and reliable approach to determining evolving
mechanical properties of films, overcoming the difficulties associated with handling
very thin free-standing films and the limited sensitivity of conventional methods,
with potential applications extending to coatings, personal care items, and foods.
controlled wetting and spreading of liquids, adhesion and assembly of smart
coatings. There is therefore a need of simple, cost-effective and scalable techniques
for pattern formation over a wide range of scales. Conventional methods
fail to comply with these requirements, as costs and complexity increase in the
attempt to impress nm to µm scale features. By contrast, wrinkling of bi-(multi-
)layers is inherently inexpensive, scalable and robust, and has the potential for soft
matter patterning from the nano- to the macro-scale. This work investigates the
controlled multi-layer generation of polydimethylsiloxane (PDMS) glassy skins via
surface oxidation using plasma exposure and/or ultraviolet ozonolysis (UVO). Uniaxial
mechanical compression is then employed to induce pattern formation via a
well-known wrinkling instability. Topographies with wavelengths down to 45 nm
are achieved, for the first time, as well as features with characteristic lengthscales
of ∼ 10s µm. Moreover, simple design routes for double frequency nested pattern
formation, imposed by compression of tri-layer laminate films, are established.
The work concludes by exploiting wrinkling as a method for the mechanical characterisation
of thin drying films. A time-resolved wrinkling interrogation during
film drying is established as a simple and reliable approach to determining evolving
mechanical properties of films, overcoming the difficulties associated with handling
very thin free-standing films and the limited sensitivity of conventional methods,
with potential applications extending to coatings, personal care items, and foods.
Version
Open Access
Date Issued
2017-06
Date Awarded
2017-09
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
License URL
Advisor
Cabral, João
Matar, Omar
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)