We recently reported a new method to prepare smooth nanocellulose (NC) films [1] by spraying the nanocellulose onto a smooth and polished surface and then allowing the film to dry in air. Spraying has a notable advantage such as contour coating and contactless coating with the base substrate. The basis weight and thickness of the NC film is tailorable by adjusting NC suspension in spraying process. NC film prepared via spray coating has unique two-sided surface roughness with the surface in contact with the surface much smoother than the air-contact side. The surface roughness is one of the controlling parameter in barrier performance of the NC film and alterations in surface roughness switches the wettability. The RMS roughness of the two surfaces investigated by Optical Profilometry was found to be 2087 nm on the rough side and 389 nm on the spray coated side, respectively. The spray coated NC film has ultra-high smoothness on the side exposed to the polished stainless steel surface. The factors including the size of cellulose fibrils and surface smoothness of base surface that control the roughness of the film are currently being investigated and will be discussed in the presentation. The surface smoothness requirements for substrate applications in SERS and printed electronics will also be discussed.

1. The ANFF & AMMRF Research Showcase
Sydney 22-23 November 2017
Make and Measure
Tuning Nanoscale Surface
Roughness and Smoothness
of Nanocellulose Film
via Spray Coating
K. Shanmugam, S.Varanasi, Gil B.D. Garnier, Warren J. Batchelor
Bio Resource Processing Research Institute of Australia (BioPRIA),
Department of Chemical Engineering,
Monash University, Clayton, Australia.

2. Cellulose nanofiber materials
Isogai et al. Nanoscale,2011,3, 71-85

3. Cellulose nanofibre applications
Aerogels/foam
Packaging
Solar Panels Air FiltrationFlexible Electronics
Oil and water separation Water Filtration

4. Spray Coating Method
Experimental Conditions :
• Spray distance - 30 cm, Suspension concentration - 1.0 to 2.0 wt %, Velocity of conveyor – 0.34 cm/sec
Conveyor and Professional
Spray system
Nanocellulose
films
Stainless
steel plate
Nanocellulose
Spraying video Drying

5. SEM Micrograph of Nanocellulose Films
Free side Plate side
1µm 1µm
Vacuum Filtration
Spray Coating
Free side Filter side
Rough surface Smooth surface

6. Investigating the surface roughness of
nanocellulose films
AFM
Optical Profilometry
Objective

7. AFM Micrograph of nanocellulose Film
Vacuum Filtration
Spray Coating
Rough surface Smooth Surface
Free side Filter side

8. Roughness from AFM Image (10µm x 10µm)
0
50
100
150
200
250
300
350
400
450RMSinnm
Nanocellulose Film Sides
Spray Coating Vacuum Filtration

9. Bruker Contour GT-I –Optical
Profiler
Optical Profilometry

10. Method Side 1 ( Rough Side) Side 2 (Smooth Side)
VF-NC
50X
SC-NC
50X

11. Roughness from Optical Profiler Image
(50X magnification)
0
500
1000
1500
2000
2500
3000
3500
4000
RMS(Rq)innm
Nanocellulose Films sides
Spray Coating
Vacuum Filtration

12. Method Side 1 ( Rough Side) Side 2 (Smooth Side)
VF-NC
20X
SC-NC
20X

13. Roughness from Optical Profiler Image
(20X magnification)
0
1000
2000
3000
4000
5000
6000
RMS(Rq)innm
Nanocellulose Films Sides
Spray Coating Vacuum Filtration

14. Method Side 1 ( Rough Side) Side 2 (Smooth Side)
VF-NC
5X
SC-NC
5X

15. Roughness from Optical Profiler Image
(5X magnification)
0
1000
2000
3000
4000
5000
6000
7000
RMS(Rq)innm
Nanocellulose Films surface
Spray Coating Vacuum Filtration

16. Films Preparation method Technique used Surface RMS Roughness
Spray Coating
Atomic Force
Microscopy
Rough 414.0 nm (10µm
x10µm)
51.4 nm (2µm x
2µm)
Smooth 81.1 nm (10µm
x10µm)
16.7 nm (2µm x
2µm)
Optical Profiler
50x Image
Rough
Smooth
2086.69 nm
389 nm
Vacuum Filtration
Atomic Force
Microscopy
Free Side 417.7 nm (10µm
x10µm)
102.3 nm (2µm x
2µm)
Filter side 330.8 (10µm x10µm) 70.7 nm (2µm x
2µm)
Optical Profiler
50x Image
Free Side
Filter Side
2673 nm
3751 nm

17. Factors Controlling Surface Roughness
Base/Contact Surface
Cellulose Fibres

18. Scope of Tailoring Surface Roughness
Use of nanocellulose in printed electronics: a
review (Fanny Hoeng et al., 2016)
Recyclable Barrier materials

19. Conclusion
 A rapid technique to prepare the nano-cellulose
film was developed.
 The spray coated film has two distinct surface.
 Roughness of the smooth side of spray coated
film is 389 nm.

20. Acknowledgement
• Melbourne centre for Nanofabrication.
• Monash Centre for Electron Microscopy.
• Ms. Natasha Yeow, AFM facilities, Monash Univ.
• Student friends and Staff members at BioPRIA.

21. Thank you
PRESENTED BY
Warren Batchelor
Deputy Director,
BioPRIA
Monash University
Australia