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Laser-induced Nanostructures as Biomimetic Model of Fluid Transport in the Integument of Animals

Periodic Reporting for period 2 - LiNaBioFluid (Laser-induced Nanostructures as Biomimetic Model of Fluid Transport in the Integument of Animals)

Reporting period: 2016-07-01 to 2018-06-30

LiNaBioFluid, “Laser-induced Nanostructures as Biomimetic Model of Fluid Transport in the Integument of Animals”, was a Research and Innovation Action funded by the European Community’s Horizon 2020 - FET Open Programme (grant agreement no: 665337), which supported early-stage research on any idea for a new technology. It brought together 7 partners from 4 different countries. The project consortium was very interdisciplinary combining renowned experts from the fields of zoology, physics, mechatronics, life sciences, materials sciences, laser-matter interaction, production technology, tribology, and biomimetics. The joint project consortium formed an excellent base for fundamental and applied research in the field of biomimetic surfaces.

LiNaBioFluid aimed on laser-fabrication of biomimetic surfaces with exceptional wetting properties, which were inspired by the integument of animals. The integument of an animal body has various functions, which are often achieved by specific micro- and/or nano- hierarchical structures. Advanced laser-processing strategies based on self-organization were employed, to mimic the specific topography and the excellent wetting properties of the integument of bark bugs and moisture harvesting lizards resulting from adaptations to their environment. The outcome of this innovative biomimetic exploitation of wetting effects is expected to lead to radically new technological approach of laser-generated surface textures on a micro- and nanometer scale. Especially from a reduction in friction and wear of optimized structures in lubricants, leveraging of new results and leading to higher efficiency by reducing energy consumption can be expected.

The project LiNaBioFluid was divided into 5 work packages (WPs). WP1 takes care of project management. WP2 concentrates on the characterization and structuring of soft organic materials as the scales from lizard exuviae, the cuticles of bark bugs and their replication. WP3 focuses on self-organized laser-induced structure formation on hard inorganic materials. WP4 aims at fabricating fast fluid transport over large areas for technological applications. The activities for dissemination and exploitation of project results are handled in WP5.

In the project LiNaBioFluid, all five intended objectives have been achieved based on the unique properties of fluid transport on the integument of flat bark bugs and moisture harvesting desert lizards:

Objective 1: Directed fluid transport starting from capillaries and then expanding to plain areas covering several square centimeters within a few seconds.
Objective 2: Speed-up of fluid transport by optimized interaction between surface wetting and topography.
Objective 3: Speed-up of fluid-transport by optimized structure geometry and shape of individual micro- and nanostructures at the surface.
Objective 4: Self-organized laser-induced structure formation resembling the bark bug design on areas of several square centimeters with short processing times.
Objective 5: Laser-structured surface on hard inorganic material with bark bug design with fast transport of lubricating fluids resulting in a significant considerable reduction of the friction coefficient compared to that of a plain surface of the same material.
"Key innovation points of WP5 ""Exploitation and dissemination"" were:
• More than 35 articles in high-ranked international, peer-reviewed scientific journals, with open access conditions (“green” or “gold” model), several invited
• Promotion of young researchers with 16 Bachelor, Master and PhD theses
• 91 oral presentations and posters by all partners at international scientific conferences and workshops, many invited
• Communication activities to the general public: Visits of fairs, newspapers and journals, TV or radio, contribution at TV channel EURONEWS ( institutional websites
• LiNaBioFluid flyer
• Social media accounts with scientific impact: ResearchGate account of LiNaBioFluid with more than 1500 “Reads” and more than 50 “Followers”
• 8 awards including the renowned International Bionic Award of the Schauenburg Foundation.
• Organization of the 6th International Workshop on Laser-Induced Periodic Surface Structures (LIPSS) in Heraklion (November 2016)), an industry-oriented Workshop “Laser Processing for Bionic Applications” in Berlin (November 2017), and organization of a special LiNaBioFluid session at the EMRS Spring Meeting 2017 in Strasbourg.
Progress beyond the state of the art: The novelty of the project was related to the use of the integument of bark bugs to design biomimetic surfaces. While most of previous research activities in the field of biomimetic fluidics focused on plants and reptile surfaces, there was very limited knowledge on bark bugs in general, which possess excellent mimicry. The fluid transport on the cuticle of (some) bugs includes the transport of the fluid out of the capillary followed by the spreading of the fluid on an extended area with microstructures. This special kind of fluid transport is assumed to be caused by the specific microstructures and/or wettability of the bark bug cuticle. The fluid transport in capillaries combined with super-wetting on large areas has application potential in the field of fluidics and microfluidics. However, it is not feasible to mimic the surface structure of the bark bug cuticle or the scale of a moisture harvesting lizard on a larger surface of several square centimeters by a scribing technique (e.g. electron beam lithography) due the long processing times required. Therefore, we employed the self-organized structures occurring on laser irradiated surfaces for structuring of surfaces on technically relevant hard materials, which show many similarities to those found in the animal integuments.

Impact: The radically new line of technology was the use of biomimetic designs, i.e. bug and lizard ones, for controlled fluid transport. The proof-of-principle was friction reduction of a surface with self-organized laser-generated nano/microstructures and the new scientific underpinning the understanding of the role of surface topography and wettability for the fluid transport out of a capillary onto a microstructured surface where the fluid spreads.
A main target of the project remained the management of wear and friction, which means saving of resources and reduction of CO2 emission. This is a very important field as estimated 5% of the gross national budget is lost every year due to wear and abrasion in industrialized countries. In even higher relative dimension are the effects with regard to energy consumption and CO2 emission. Additionally to reduction of energy consumption and CO2 emission, the project success was directly correlated with further societal challenges the EC is straggling with as health/demographic change issues. Patients in hospitals or at home could benefit from implants consisting of Titanium with laser-induced microstructures at their surface which can be not only wetted by blood and body fluids, but at the same time prevents the overgrowth by tissue and cells. Another un-expected result were anti-reflection properties of bio-inspired laser-induced microstructures.
Coefficient of friction on fs laser-processed Ti (
The laser structured logo of the LiNaBiofluid; A one-year old Lizard is reflecting on the sample.
Image of the south American flat bug Dysodius lunatus
Wear tracks on laser-induced periodic surface structures (
Structures of lizards are mimicked by laser-processing
Directional flow of dyed soapy water against gravity due to tilted laser-induced cones on polyimide
fs laser-processed steel samples with laser-induced periodic surface structures or grooves