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Design and Fabrication of Functional Surfaces with Controllable Wettability, Adhesion and Reflectivity

Periodic Reporting for period 2 - FabSurfWAR (Design and Fabrication of Functional Surfaces with Controllable Wettability, Adhesion and Reflectivity)

Reporting period: 2017-01-01 to 2018-12-31

The potential for deliberately created engineered surfaces has not been explored to any notable extent, yet there is strong evidence suggesting that significant gains can be achieved in terms of anti-bacteria, low adhesion and friction, de-icing, and self-cleaning. The project “Design and Fabrication of Functional Surfaces with Controllable Wettability, Adhesion and Reflectivity (FabSurfWAR)” provides staff exchange between the partners of EU and Asia and engenders the development of key enabling techniques for designing and generating micro/nano surface topology with better control of bacterial growth, adhesion, friction and other tribological properties. The potential applications range from surgical tools and biomedical devices to turbine blades and agricultural machines.

FabSurfWar has established a long-term international and inter-sector collaboration consortium for staff exchanges in research and innovation between ten world-recognised institutions across the EU and Asia in the cutting-edge research area of micro/nano surface engineering with promising applications in scientific and engineering sectors. The synergistic methodologies achieved by FabsurfWAR will serve as the building blocks of the micro/nano functional surface design, fabrication, measurement, characterisation and scale-up application. Consequently it positions the consortium as a scientific and technological leader in functional surfaces and their potential applications.

The project has delivered 141 person-months of seconded research between the EU beneficiaries and Asian partners; it has authored 2 chapters in books; published 78 peer-reviewed journal publications and delivered 35 conference papers. It has also registered 19 patent applications.
All the FabSurfWAR tasks for the period from 1 January 2015 to 31 December 2018 described in the proposal have been carried out and successfully completed as planned. The project has developed world-class processes for the design, fabrication, measurement and characterisation of functional surfaces with controllable wettability, adhesion and reflectivity. Scientific progress has been achieved in the following areas:

• Various functional surface modelling and fabrication technologies have been reviewed, and the database for functional surfaces has been set up. Road maps for future controllable functional surface design and fabrication technologies have been established. Surface modelling, characterisation and fabrication technologies have been studied. The correlation between the surface topography and the wettability has been studied. Influences of the pillar shape on the wettability, adhesion and reflectivity have also been explored.

• Bionic methodologies to generate and represent the functional surfaces have been studied. The functional surfaces exhibited by some soil-burrowing insects for their anti-adhesion/anti-contamination performances have been investigated and sample tools developed.

• Different advanced laser processing structuring technologies: direct laser interference patterning (DLIP) and ultrafast laser-induced mirco/nano structuring and direct laser structuring were explored. Various types of nano/micro-scaled surface structures/patterns on metallic surfaces were generated by utilizing three different types of lasers: femtosecond laser, nanosecond laser and excimer laser. All these techniques can be used to generate controllable hydrophobicity.

• The cheap and easy ways for making structure surface on fairly large scales have also been investigated. These cover more conventional methodologies from mechanical machining technologies including milling, turning and grinding to Wire Electrical Discharge Machining (WEDM). The influence of the machining parameters on the surface topography and further on the wettability have been examined in micro and nano scales.

• The Nanolithography and Atomic Force Microscope (AFM)-based nano-fabrication were also utilized to fabricate nanorods, nanopillars, flat nanopatterns of triangles and circles and nanobows on the materials including silicon, SU-8 resist, polymers, nickel and PDMS.

• Surface coating and deposition techniques have been applied to produce antimicrobial surface and control wetting via controlling of surface chemistry and topography. E. Coli bacteria were tested on the structured stainless steel surfaces. Zinc oxide films with three types of nanotopographies: needle-like and hexagonal nanorods and flakes, were prepared by hydrothermal synthesis on stainless steel substrates to investigate their photocatalytic and antibacterial properties. The results showed that photocatalytic activity was clearly influenced by the nanotopography.

• AFM is used both as a sensor and as an actuator, for nano-handling of nanoscopic and biological objects. AFM is also used for nanoindentation, material processing and cutting of nano-objects like DNA.
The project has successfully completed all the planned research and implementation tasks. Since the start of the project on 1st January 2015, it has produced:

• Publications: 78 journal papers.
• Patents: 5 in UK and 14 in China.

The publications have appeared in many leading high-impact journals including Applied Surface Science, Journal of Colloid and Interface Science, ACS Applied Materials and Interfaces, Mechanics of Composite Materials, IET Nanobiotechnology, Advanced Engineering Materials, Journal of the Mechanical Behaviour of Biomedical materials, Journal of Laser Applications, Advances in Mechanical Engineering, IEEE/ASME Transactions on Mechatronics, International Journal of Agricultural & Biological Engineering.

The project also organised 6 special conference sessions based on the research work of the FabSurfWAR project, in particular at the annual IEEE International Conference on Manipulation, Manufacturing and Measurement on the Nanoscale (3M-NANO), resulting in the publication of 35 conference papers.

The development of functional surfaces has led to commercial exploitation. To-date 19 patent applications have been filed with 5 in the UK and 14 in China.
One of the applications of the functionalized surfaces is in air bearings, where micro surface features are generated to form air films and lift up a shaft to spin freely. The preliminary results show that the functionalised surfaces are very effective in bearing performance. A commercial exploitation plan has been created to facilitate the production of engine turbochargers supported by air bearings, as a result a diesel engine is up to 40% more fuel efficient and produces 50% less CO2 and NOx emissions than a standard one of the same power.
Patterned surfaces produced by multi-laser beam interference
FESEM images of ZnO coatings
: Integration of a nitride NanoBit and an AFM probe using a topology-optimized microgripper.
SEM image and contact angle of laser interference lithography
laser induced periodic patterns and contact angles
SEM images of laser ablated surface on Ti-6Al-4V
Contact angle increase against time
Patterned surfaces produced by two-laser beam interference
Self-clean surfaces of lotus leave
Bionic application