- Laser-generated ultrasound study #3: 200 micron fibres: MWCNT + PDMS, 1, 2, …7 dips MWCNTs all with PDMS overcoat. Compare to previous integrated fibre. Study indicates that subsequent dips into MWCNT/xylene solution do not significantly enhance ultrasound generation. Further coatings developed using 1 x MWCNT dip and PDMS overcoat.
- MWCNT films onto thin cover slips for further measurements – both integrated coatings and bilayer coatings. Achieved using dip coating deposition technique.
- Note that the MWCNT coating on fibres have coffee ring effect – thicker MWCNT coating around the fibre circumference and patchier coating in the fibre centre. Research into inkjet printing techniques to overcome coffee ring effects. Use of dual solvent combination – explore range. For aqueously dispersed nanotubes, the use of a water/MeOH combination eradicates coffee ring effect (1:1). For xylene dispersed nanotubes, xylene/acetone combination (2:1). Interestingly, fMWCNT/ xylene + acetone combination results in the formation of a gel like material. Fibres dipped in this gel show no coffee ring effect with a very dense nanotube mesh at the fibre tip.
- ‘Scratch test’ – Fibres coated with MWCNTs and PDMS overcoat tested against sellotape and a surgical scalpel to determine coating robustness. Coatings remain adhered to fibre upon repeated exposure to Sellotape. Forceful use of scalpel effects some coating damage but does not completely destroy it.
- Characterisation: Raman, UV Vis (absorption and transmission measurements), Optical microscopy (stereo microscope), Scanning electron microscopy, AFM, ATR-IR spectroscopy.
- Preliminary incorporation of AuNPs, Au nanorods, dyes and QDs into PDMS but concentrations too low. Optimisation area for future work
Sacha Noimark
Sacha Noimark, April 2015: Optimisation of MWCNT-PDMS coatings on optical fibres