Ultrashort pulsed laser structuring of Biomimetic Surfaces

The study and simulation of biological systems is popularly known as biomimetics - a combination of the Greek words ‘bios’, meaning life, and ‘mimesis’, meaning to imitate. Nature offers a wealth of diverse functional surfaces, whose properties are unmatched in today’s artificial materials. In this context, a highly interdisciplinary field of research has emerged concerning the design, the synthesis and the fabrication of biomimetic structures, based on the ideas, concepts and underlying principles developed by nature. Biomimetic materials provide innovative solutions for the design of a new generation of functional materials and can lead to novel materials design principles.

Wetting response and SEM pictures of actual lotus leaf (left) and fs treated silicon (right) surfaces

Bionics and biomimetics are disciplines with high potentials for technical innovation. In this context, several methodologies have been developed to facilitate the formation of bioinspired constructs, exhibiting hierarchical structuring at length scales ranging from hundreds of nanometers to several microns. Laser processing is a highly versatile approach allowing bottom-up and top-down structuring, while it excels over mechanical, chemical and electric discharge texturing, as it enables localized modifications with a large degree of control over the shape and size of the features that are formed and a broader range of sizes that can be fabricated.

This lecture will review the development of of novel ultrafast pulsed laser processing schemes for the controlled fabrication and engineering of biomimetic surfaces to realize extraordinary optical, wetting, biological and tribological properties, for a variety applications, including special optics, microfluidics, flexible optoelectronics and tissue engineering. In parallel, the biological principles behind the functionalities exhibited by the natural surface archetypes will be analysed and discussed.  In particular, by applying ultrafast laser pulses novel surface structures with sub-micron sized features are produced while the physical properties of semiconductor, dielectric and metallic surfaces are significantly modified.

 The biomimetic surfaces developed exhibit controlled dual-scale morphology, that mimics the hierarchical structuring of natural surfaces with exciting properties (i.e. the Lotus Leaf, the Shark Skin, Lizards’ Integument and Cicada wings).

SEM images of actual shark skin (left) and of an fs treated metal surface (right)

As a result, the biomimetic morphology attained gives rise to notable multifunctional properties including water repellence, self-cleaning, antibacterial, anti-friction, anti-fogging, anti-reflection and combination of those (b) smart, i.e show the ability to change their functionality in response to different external stimuli. At the same time, the ability to tailor the morphology and chemistry is an important advantage for the use of the biomimetic structures as models to study the dependence of growth, division and differentiation of cells on the surface energy of the biomimetic cell culture substrates used for tissue regeneration.

SEM images of actual Cicada Cretensis wing (left) and of an fs treated glass surface (right). Photograph of half-treated glass with reduced light reflection (below).

Besides presenting the potential and significance of the laser based biomimetic surface structures, it will also delineate existing limitations and discuss emerging possibilities and future prospects.

BIO:

Dr. Emmanuel Stratakis is a Research Director at the Institute of Electronic structure and laser (IESL) (www.iesl.forth.gr) of the Foundation for Research and Technology—Hellas (FORTH) (www.forth.gr). He received his Ph.D. in Physics from the University of Crete in 2001 from the Physics Department, University of Crete. After graduating, he joined as a visiting Researcher the IESL-FORTH working on the ultrafast laser engineering of materials and as an Adjunct Professor at the Department of Materials Science and Technology, University of Crete. In the fall semesters of 2006 and 2008 he was appointed as a visiting Researcher at the Department of Mechanical Engineering of the University of California, Berkeley. In 2007 he was elected Researcher at IESL-FORTH where he is leading the “Ultrafast Laser Micro- and Nano- processing” laboratory (http://stratakislab.iesl.forth.gr;https://www.iesl.forth.gr/en/research/ULNMP-Group). His research interests are in the fields of ultrafast laser interactions with materials for (a) biomimetic micro- and nano- structuring (b) Advanced photonic processes for photovoltaics and energy storage, c) nanomaterials synthesis and diagnostics for optoelectronics and (c) biomaterials processing for tissue engineering. He has delivered more than 50 invited and keynote lectures and has been organizer and chair in major international scientific conferences. He has over 230 SCI publications and more than 8000 citations, h-index=48 (Scopus), and he has coordinated many National and EU grants. Since 2015, he is the Director of the Nanoscience Facility of FORTH, part of the NFFA-Europe EU Infrastructure, where he is a member of the General Assembly. Stratakis is founder of Biomimetic, a spin-off company of FORTH providing bioinspired laser induced nanotextured glass to present optimal combinations of anti-reflective, anti-glare, anti-fogging, antibacterial and antimicrobial properties. He is a National Representative to the High-Level Group of EU on Nanotechnologies, Advanced materials, Biotechnology, Advanced Manufacturing and Processing. He is a member of the Scientific Committee of COST.