Biography:
Hassan Zahouani is a Professor at the National School of Engineers of Saint-Etienne (internal school of the Ecole Centrale de Lyon) since 1991 (Exceptional Class 1 & 2). He is an Associate Professor at the University of Halmstad and President of the Francophone Society of Engineering and Skin Imaging. In 2022 he was ranked by the American University Stanford as one of the 160,000 most cited researchers in the world. In 2023 he was designated as a Fellow of the Carnot Institute in Lyon, for the expertise acquired worldwide in the mechanics and imaging of living tissues.
His research work within the Laboratory of Tribology and Dynamics of Systems concerns the contact mechanics of rough surfaces and their implications in the various fields of tribology, archeology, and health. The development of the concept of multi-scale characterization of surface topography by continuous wavelets has been the subject of several publications and international conferences, on industrial issues that are still topical, such as surface finishing, lapping, wear, and the identification of relevant scales in the field of traceology in archaeology, the complexity of biological surfaces.
Since 2000, he has initiated an innovative axis of research concerning bioengineering and multi-scale imaging of living tissues. The scientific challenge in the issue of living organisms is to comprehend the key mechanical role of the fascia, which is the fibrillar membrane supporting all living tissues. This connective tissue is considered today one of the most important and complex sensory organs of the human body. The creation of the Bioengineering and Perception platform within the LTDS has been at the origin of several innovations and patents for the objectification of viscoelastic palpation (UnderSkin©) of skin pathologies and touch by the TouchyFinger© device. This activity has initiated many industrial and academic collaborations in France and internationally.
The development of multi-scale imaging for the analysis and quantification of biophysical markers of tissue sublayers has been the subject of the development of new multi-scale approaches for the diagnosis and quantification of descriptors of internal tension forces of the different layers of living tissue (LC-OCT tomography, two-photon confocal tomography, high-resolution ultrasound echography, etc.).
Particular attention has been paid to the superficial fascia that envelops the living tissue. Fascia is the fundamental connective tissue in human life (80th Organ of our Body). It is a fibro-elastic membrane that envelops the entire human anatomical structure. It is, thus, accepted that our body is a fibrillar network from the skin's surface to the depths of the bone and the cells. Everything is linked by a fibrillar organization whose diameter is extremely variable but continuous in the terms of the mechanics of continuums. Fascia wraps the skin, muscles, nerves, bones, blood vessels, lymphatic system, arteries, spinal cord, brain, and organs. Hereditary diseases of the connective tissue or collagenopathies group together diseases by mutation of one of the genes encoding collagen. The main manifestations are abnormalities in the bones, joints, skin, vessels, waist, or face. The fascia defined as supporting tissue is probably the source of the natural tension forces of all our human tissues. For skin tissue, the effect of the tension forces of the connective tissue fibrillar network is visible on the skin surface topography as a network of tension forces from head to foot. One of the challenges of our current research is to understand Fascia mechano-transduction through the development of mechanobiology coupled with high-resolution imaging. This transduction mechanism is the basis of all human senses, its understanding in tactile perception is a fundamental and multidisciplinary subject, especially in the analysis of tactile comfort by tribo-transduction which by friction and vibration stimulates the cutaneous mechanoreceptors in a wide range of frequencies.
HONORS:

• Associate Professor at Halmstad University
• President of the French Society of Engineering and skin imaging (created since 1999)
• Ranking by the American University Stanford as one of the 160,000 most cited researchers in the world (2022).
• Designation as a Fellow of the Carnot Institute in Lyon, for the expertise acquired worldwide in the mechanobiology and imaging of living tissues (2023).
• Founding Member of the International Journal Surface Topography
• Member of the editorial board of the journal surface topography
• Member of the steering committee of the Metrology and Properties of Engineering Surfaces Conference
• Chairman of six international conferences
• Best Paper Award. “H. Zahouani & al, Effect of roughness on vibration of human finger during a friction test”. 19th International Conference on WEAR OF MATERIALS. Portland, Oregon, USA. April 14-18, 2013
• Prize for the best paper awarded by the International Society of Bioengineering and Imaging of skin: “H. Zahouani & al, Maturation of skin tension in newborns: Characterization and modeling”. San Diego. June 2018,
• Innovation award for the TouchyFinger© device by the international jury of Cosmetic Valley, 2021
• President of the humanitarian association for the rural population of Morocco “Treatment of the Eye and Skin”

Keynote title: Surface topography and multi-physics functionality of engineering and living surfaces
Abstract:
For many years, some engineers believed that smooth surfaces are better for contact and friction. Several events changed this view, one very dramatically. It happened in 1930 when Bentley engines, which were manufactured with exceptionally smooth cylinder walls, seized up during the Le Mans 24-hour race. There followed a concerted effort to better understand the role of surface texture and to quantify it in ways that were meaningful to manufacturing. Initially, optical microscopes were employed to provide a magnified view of surface characteristics. Again, measurement was comparative and somewhat subjective, but the various degrees of magnification and the differing fields of view afforded led to the concept of sampling lengths and frequency that are central to surface analysis today. Other early efforts to capture information about a surface utilized a trace stylus and a mechanical “amplifier” which used linkage to replicate the trace onto a smoked glass surface.
In 1933, E. J. Abbot developed what is widely believed to have been the first analog surface instrument. This used a stylus to contact the part and provided an actual number to quantify texture. Abbot also co-developed the Abbot-Firestone curve. This used a simple curve to represent the surface and made contact area the basis of the curve, allowing the calculation of a material-to-air ratio as a function of depth. This was the first instrument to link form with function in a numerical manner simple enough to quantify a surface and help control manufacturing processes.
Metrologists today often categorize the data from a measured surface into three categories-roughness, waviness and form. Shorter wavelength data tends to reflect surface roughness characteristics imposed by machining operations, such as turning, grinding or polishing. Waviness involves longer wavelength data and might reflect instabilities in the machining process, such as imbalance in a grinding wheel or worn spindle bearings. Long wavelength data tends to reflect errors, such as lack of straightness in the guideways of a machine or misalignment of machine axes.
The whole history of engineering surfaces can be presented in the form of bands of wavelengths or spatial frequencies. International standards have defined the wavelength bands of surface roughness, waviness, and shape. This spatial information has been at the origin of the development of digital filters based on signal and image processing tools, operating by signal decomposition. The most famous is the Fourier transform (1807). Joseph Fourier defined the time-frequency duality, which is for surface topography, the length and the spatial frequency. This major transform has been used in all areas of physics and dimensional metrology. To improve frequency localization, wavelet analysis appeared in its “modern forms” at the beginning of the 1980s, in a remarkable article by Alex Grossman and Jean Morlet. One of the essential points that this decomposition teaches us is that a mathematical object (whether it is a function, a signal, an image, an operator…) can be represented in multiple ways, each of these representations making it possible to emphasize certain characteristics. in the modern characterization of surface topography, this tool performs multi-resolution analyzes and the development of multi-scale microscopy. The decomposition by continuous wavelets is a powerful tool for the comparison of images in a large-scale (roughness, undulation and shape), as well as the study of aging and wear of inert or living surfaces.
For a better understanding of surface topography, Fourier and continue wavelet transform tools, will be illustrated in this work by applications in several areas of surface functionality, contact mechanics and friction modelling. The recourse to the mathematical morphology and to the fractal character of surfaces, offers a new way of studying new parameters which allow the cohesive character of the topography and its use in the analysis of the aging of surfaces and their wear in various fields.