New paradigms for the design, manufacturing and operation of food processing and packaging equipment 4th Presentation of Final Workshop PARADIGM 1 DEMONSTRATOR ELEMENTS Aimed at the rationalization of components and cost, increase of yield and of hygienic design Pulsed-laser treatment to increase surface hydrophobicity Project web site: http://www.npfp.it/en

1. Dr. Gianmarco Lazzini
Centro SITEIA.PARMA - Università di Parma
Ultrashort-pulsed-laser textured tunnel and pipe outer
surfaces:
pulsed-laser treatment to increase the surface hydrophobicity

2. NPFP 2
Ultrashort-Pulse Laser Texturing
During the light-matter interaction, the lattice remains cold  No fusion of the target
Laser texturing: generation of self-organized structures driven by the light-matter
interaction at intensities equal or slightly above the ablation threshold (0.1 J/cm2)
Ultrashort pulses: duration < 1ps
(http://www.industrial-
lasers.com)
(A. Weck et al., Appl. Phys. A
90, 537 (2008))
Copper, E = 10 μJ, 30000
pulses, τ = 150 fs
Copper, E = 10 μJ, 30000
pulses, τ = 7 ns

3. NPFP 3
Ultrashort-Pulse Laser Texturing
Possibility to realize biomimetic hierarchical surfaces in a single step process
Lotus leaf Tetrodontophora bielanensis
(E. Fadeeva et al., Langmuir 27, 3012 (2011))
(F. A. Müller et al., Materials 9, 476 (2016))
(https://www.lightmotif.nl)

4. NPFP 4
Ultrashort-Pulse Laser Texturing
Strengths:
• Single step process;
• Achievable on several materials (conductors, semiconductors etc.);
• Achievable without the need of clean room facilities, in air or other
gaseous atmospheres;
• Achievable both on curved and planar surfaces;
• The surface morphology can be easily varied by tuning the laser
parameters (light polarization, fluence, incidence angle etc.)

5. NPFP 5
Ultrashort-Pulse Laser Texturing
Applications:
• Modification of the surface
optical properties
• Modification of the surface
tribological properties
• Cellular adhesion
(G. Li et al. Appl. Phys. A 118, 1189 (2015))
(G. Lazzini et al., Surf. Topogr.: Metrol. Prop. 5, 044005
(2017))
(J. Bonse et al. Appl. Phys. A 117, 103 (2014))

6. NPFP 6
Fabrication Technique
Material: AISI 316L stainless steel
Processing parameters:
• Single pulse duration: < 400 fs
• Wavelength: 1030 nm
• Repetition rate (RR): 100 kHz – 1 MHz
• Scanning speed (v): 20 – 200 cm/s
• Fluence:
• Horizontal overlap: (fixed to 92%)
• Vertical overlap: (fixed to 80%)
• Total processed surface: 8 mm × 8 mm
• The scanning was repeated 20 times
2
0
E
F  (0.36 – 2.33 J/cm2)
100
0
0




 d
HOL
100
0
0




 h
VOL
d = 2 μm
ω0 = 25 μm
v

h = 5 μm

7. NPFP 7
RR=1MHz,v=200cm/sRR=500kHz,v=100cm/s
Transition LIPSS  bumps
Fluence = 0.36 J/cm2 Fluence = 0.48 J/cm2 Fluence = 0.69 J/cm2
20 μm
20 μm20 μm20 μm
20 μm20 μm
5 μm
5 μm
Micro-ripples
Results – SEM images
LIPSS

8. NPFP 8
Results – Topographical analysis
Fluence = 0.36 J/cm2
RR = 1 MHz, v = 200 cm/s
20 μm
20 μm20 μm20 μm
20 μm20 μm
Shear Force Microscopy (ShFM)

9. NPFP 9
Results – Topographical analysis
20 μm
20 μm20 μm20 μm
20 μm20 μm
5 μm
Transition LIPSS  bumps
RR = 500 kHz, v = 100 cm/s

10. NPFP 10
Results – Metrological analysis
• Local minimum in the RMS
roughness as a function of
fluence at ≈ 0.85 J/cm2 (at which
the transition LIPSS  bumps is
observed)
• At the same fluences, a jump
in the Motif mean slope is
oberved  coalescence of
surface structures

11. NPFP 11
Results – Wettability
• Increasing of the water static
contact angle (CA) by aging in air
Transition from hydrophilic to
superhydrophobic
• The asymptotic CA can be
controlled by varying the
chemical composition of the
aging atmosphere
• The laser processing increases
the asymptotic CA to values
compatible with a
superhydrophobic behaviour

12. NPFP 12
Results – Wettability

13. NPFP 13
Results – Wettability
Wettability with milk (ECOR)  experimental procedure
Tilt angle: 50° (fixed)
Liquid: Whole milk (10 µL)
Sample direction: 0° (direction 1)
90° (direction 2)
Preliminary
cleaning with
ethanol for 1 min
Put the milk drop
Dirty area
(picture)
Binary image
ImageJ software:
Images analysis

14. NPFP 14
Results – Wettability
The sample
direction influences
the sliding of the
milk drop
Wettability with milk  Results
Direction1
Direction1
Direction 2
2 1
Direction2
Isotropic
texture
Direction2Direction1
Anisotropic
texture
2
1

15. NPFP 15
Conclusions
• Ultrashort laser texturing is a powerful approach for the
realization of a large variety of textures over several materials.
This technique is particularly promising for processing in an
industrial context, due to its simplicity
• Ultrashort laser textured surfaces show intresting physico-
chemical properties for multiple technological applications, e. g.
superhydrophobicity
• Further efforts are needed in order to clarify which are the most
effective experimental conditions to obtain the required
properties, and to realize laser facilities whose processing times
are compatible with industrial requirements

16. NPFP 16
Participants to this activity
• Luca Romoli, Gianmarco Lazzini
Federica Bondioli
• Domenico Stocchi, Ivan Moretti
• Rossana Borgese, Paolo Lardi,
Stefano Pini, Stefano Bernini
Thanks you for your attention!
www.npfp.it