Sacha Noimark, Feb 2015: Developing new coating strategies for laser generated ultrasound, using MWCNTs and PDMS

• Synthesis of an oleylamine functionalised-pyrene ligand for the functionalisation of multiwalled carbon nanotubes, for dispersion in xylene.
• Optimisation of nanotube : functionalising ligand to maximise MWCNT dispersion concentration.
• Optimised MWCNT concentration at 14 mg /mL.
• Explore different techniques for depositing MWCNTs onto glass substrates, with a view to translate to optical fibres. Techniques explored include: dip coating, drop casting, microplotting (training required).
• Explored use of electrospinning as an alternative deposition technique. Experimented with electrospinning random meshes of PEO for optimisation of polymer solution concentration.
• For simplicity, chose dip coating strategy for nanotube deposition onto planar substrates. Development of bilayer ultrasound generation coating: MWCNT coating + PDMS overcoat. Increases efficiency of MWCNT usage; rather than direct integration of MWCNT into fast curing PDMS, dip into MWCNT/xylene and then overcoat.
• Note that MWCNT do not adhere well to the glass – form nice film but scratches off. Tried pretreating with commercially acquired paint formulation. Using this strategy, achieve good nanotube adhesion.
• PDMS overcoat forms protective layer over nanotubes. Resistant to gentle scratching, but not as strong as integration MWCNT+PDMS coating. Experimentation with PDMS dipping time to determine if this is a factor we can tune to increase PDMS adherence to glass.
• Further work on enhancing adhesion of PDMS to glass substrate: use of plasma treatment (may re-visit later for use as tool to increase polymer hydrophilicity); Use of silicone primer (apply pre-MWCNT dip, post-MWCNT dip); Piranha treatment of glass. Preliminary work on enhancing hydrophilicity of PDMS: tried incorporation of TiO2 and SiO2 NPs into PDMS – no significant impact.
• Laser-generated ultrasound study #1: 100 micron fibres: a) MWCNT dip + paint post-coat, b) MWCNT dip + PDMS post-coat, c) Paint pre-dip + MWCNT dip + paint post-dip, d) Paint pre-dip + MWCNT dip + PDMS post-dip. Although paint pre-treatment aids MWCNT adhesion, impacts on LGUS.
• Tools used for materials characterisation: UV Vis (absorption and transmission measurements), optical microscopy (stereo microscope), Scanning electron microscopy (training)

 

Sacha Noimark