Wrinkles Riding Waves in Soft Layered Materials

The formation of periodic wrinkles in soft layered materials due to mechanical instabilities is prevalent in nature and has been proposed for use in multiple applications. However, such phenomena have been explored predominantly in quasi-static settings. In this work, we measure the dynamics of soft elastomeric blocks with stiff surface films subjected to high-speed impact, and observe wrinkles forming along with, and riding upon, waves propagating through the system. We analyze our measurements with large-deformation, nonlinear visco-hyperelastic Finite Element simulations coupled to an analytical wrinkling model. The comparison between the measured and simulated dynamics shows good agreement, and suggests that inertia and viscoelasticity play an important role. This work encourages future studies of the dynamics of surface instabilities in soft materials, including large-deformation, highly nonlinear morphologies, and may have applications to areas including impact mitigation, soft electronics, and the dynamics of soft sandwich composites

Longitudinal Eigenvibration of Multilayer Colloidal Crystals and the Effect of Nanoscale Contact Bridges

Longitudinal contact-based vibrations of colloidal crystals with a controlled layer thickness are studied. These crystals consist of 390 nm diameter polystyrene spheres arranged into close packed, ordered lattices with a thickness of one to twelve layers. Using laser ultrasonics, eigenmodes of the crystals that have out-of-plane motion are excited. The particle-substrate and effective interlayer contact stiffnesses in the colloidal crystals are extracted using a discrete, coupled oscillator model. Extracted stiffnesses are correlated with scanning electron microscope images of the contacts and atomic force microscope characterization of the substrate surface topography after removal of the spheres. Solid bridges of nanometric thickness are found to drastically alter the stiffness of the contacts, and their presence is found to be dependent on the self-assembly process. Measurements of the eigenmode quality factors suggest that energy leakage into the substrate plays a role for low frequency modes but is overcome by disorder- or material-induced losses at higher frequencies. These findings help further the understanding of the contact mechanics, and the effects of disorder in three-dimensional micro- and nano-particulate systems, and open new avenues to engineer new types of micro- and nanostructured materials with wave tailoring functionalities via control of the adhesive contact properties

Topology optimization of nonlinear periodically microstructured materials for tailored homogenized constitutive properties

A topology optimization method is presented for the design of periodic microstructured materials with prescribed homogenized nonlinear constitutive properties over finite strain ranges. The mechanical model assumes linear elastic isotropic materials, geometric nonlinearity at finite strain, and a quasi-static response. The optimization problem is solved by a nonlinear programming method and the sensitivities computed via the adjoint method. Two-dimensional structures identified using this optimization method are additively manufactured and their uniaxial tensile strain response compared with the numerically predicted behavior. The optimization approach herein enables the design and development of lattice-like materials with prescribed nonlinear effective properties, for use in myriad potential applications, ranging from stress wave and vibration mitigation to soft robotics

Dependence of the kinetic energy absorption capacity of bistable mechanical metamaterials on impactor mass and velocity

Using an alternative mechanism to dissipation or scattering, bistable structures and mechanical metamaterials have shown promise for mitigating the detrimental effects of impact by reversibly locking energy into strained material. Herein, we extend prior works on impact absorption via bistable metamaterials to computationally explore the dependence of kinetic energy transmission on the velocity and mass of the impactor, with strain rates exceeding $10^2$ s$^{-1}$. We observe a large dependence on both impactor parameters, ranging from significantly better to worse performance than a comparative linear material. We then correlate the variability in performance to solitary wave formation in the system and give analytical estimates of idealized energy absorption capacity under dynamic loading. In addition, we find a significant dependence on damping accompanied by a qualitative difference in solitary wave propagation within the system. The complex dynamics revealed in this study offer potential future guidance for the application of bistable metamaterials to applications including human and engineered system shock and impact protection devices

An opto-acoustic microscope based on picosecond ultrasonics for single cell ultrasonography

L’adhésion et les propriétés mécaniques des cellules jouent un rôle crucial dans le fonctionnementcellulaire ainsi que dans l’apparition de maladies dégénératives. Pour mesurer ces quantités, nousavons développé dans ce travail un microscope opto-acoustique pour l’imagerie non-invasive de lamécanique de cellules individuelles avec une résolution sub-cellulaire. Ce microscope utilise latechnique d’acoustique picoseconde qui permet de générer et détecter optiquement des ondesacoustiques avec une large bande s’étendant jusqu’à 1 THz. Dans le but de reproduire lecomportement mécanique des cellules à des fréquences acoustiques supérieures à 10 GHz, uneétude sur des objets mous biomimétiques est menée dans une première partie. Les rigidité, viscositéet épaisseur de ces systèmes multicouches micrométriques sont caractérisées. Dans la deuxièmepartie de ce manuscrit, la technique d’acoustique picoseconde est employée pour imager le contactentre une cellule animale modèle et un biomatériau, ainsi que l’impédance acoustique de cette cellule.Un outil d’analyse nécessaire pour le traitement du signal acoustique est mis en place. Enfin, unmicroscope opto-acoustique opérationnel entre 10 et 100 GHz est présenté dans la dernière partie. Ilest basé sur un dispositif pompe-sonde asynchrone qui permet de produire des images acoustiquesen un temps court (4 pixels/min) avec une résolution axiale de l’ordre d’une dizaine de nm. Cetteapproche est comparable à une échographie mais à l’échelle cellulaire. L’étude de l’adhésion et despropriétés mécaniques de plusieurs types de cellules à différents stades de maturation est abordée.Des images topographiques des zones fines (< 50 nm) d’une cellule sont également analysées. Lemicroscope développé durant cette thèse offrira la possibilité d’explorer de nouvelles pistes derecherche dans les domaines de la biologie cellulaire et des biotechnologies.Adhesion and mechanical properties of cells are key players in several cellular functions and areinvolved in the development of degenerative diseases. To characterize these quantities, we developedin this work an opto-acoustic microscope for the non-invasive imaging of the mechanics of individualcells with a sub-cell resolution. This microscope uses the Picosecond Ultrasonics (PU) technique thatallows optical generation and detection of acoustic waves with a large bandwidth up to 1 THz. In orderto reproduce the mechanical behaviour of cells at acoustic frequencies greater than 10 GHz, a studyof cell-mimicking micro-objects is first considered. The rigidity, viscosity and thickness of these microlayeredstructures are characterized. In the second part of this manuscript, the PU technique isapplied for imaging the contact between a simple animal cell and a biomaterial, as well as the acousticimpedance of this cell. An essential tool for analysing the acoustic signal is developed. In the thirdpart, the opto-acoustic microscope operating between 10 and 100 GHz is finally presented. It is basedon an asynchronous pump-probe setup that allows producing acoustic images within a short time (4pixels/min) and offering an axial resolution of about 10 nm. This is similar to cell ultrasonography. Thestudy of the adhesion and of the mechanical properties of different cell types at different stages of cellmaturation is then tackled. The topographic images of thin cell regions (< 50 nm) are also analysed.The microscope implemented during this thesis should offer the possibility of exploring new avenuesin the field of cellular biology

Microscope opto-acoustique utilisant la technique d'acoustique picoseconde pour l'échographie cellulaire

Adhesion and mechanical properties of cells are key players in several cellular functions and areinvolved in the development of degenerative diseases. To characterize these quantities, we developedin this work an opto-acoustic microscope for the non-invasive imaging of the mechanics of individualcells with a sub-cell resolution. This microscope uses the Picosecond Ultrasonics (PU) technique thatallows optical generation and detection of acoustic waves with a large bandwidth up to 1 THz. In orderto reproduce the mechanical behaviour of cells at acoustic frequencies greater than 10 GHz, a studyof cell-mimicking micro-objects is first considered. The rigidity, viscosity and thickness of these microlayeredstructures are characterized. In the second part of this manuscript, the PU technique isapplied for imaging the contact between a simple animal cell and a biomaterial, as well as the acousticimpedance of this cell. An essential tool for analysing the acoustic signal is developed. In the thirdpart, the opto-acoustic microscope operating between 10 and 100 GHz is finally presented. It is basedon an asynchronous pump-probe setup that allows producing acoustic images within a short time (4pixels/min) and offering an axial resolution of about 10 nm. This is similar to cell ultrasonography. Thestudy of the adhesion and of the mechanical properties of different cell types at different stages of cellmaturation is then tackled. The topographic images of thin cell regions (< 50 nm) are also analysed.The microscope implemented during this thesis should offer the possibility of exploring new avenuesin the field of cellular biology.L’adhésion et les propriétés mécaniques des cellules jouent un rôle crucial dans le fonctionnementcellulaire ainsi que dans l’apparition de maladies dégénératives. Pour mesurer ces quantités, nousavons développé dans ce travail un microscope opto-acoustique pour l’imagerie non-invasive de lamécanique de cellules individuelles avec une résolution sub-cellulaire. Ce microscope utilise latechnique d’acoustique picoseconde qui permet de générer et détecter optiquement des ondesacoustiques avec une large bande s’étendant jusqu’à 1 THz. Dans le but de reproduire lecomportement mécanique des cellules à des fréquences acoustiques supérieures à 10 GHz, uneétude sur des objets mous biomimétiques est menée dans une première partie. Les rigidité, viscositéet épaisseur de ces systèmes multicouches micrométriques sont caractérisées. Dans la deuxièmepartie de ce manuscrit, la technique d’acoustique picoseconde est employée pour imager le contactentre une cellule animale modèle et un biomatériau, ainsi que l’impédance acoustique de cette cellule.Un outil d’analyse nécessaire pour le traitement du signal acoustique est mis en place. Enfin, unmicroscope opto-acoustique opérationnel entre 10 et 100 GHz est présenté dans la dernière partie. Ilest basé sur un dispositif pompe-sonde asynchrone qui permet de produire des images acoustiquesen un temps court (4 pixels/min) avec une résolution axiale de l’ordre d’une dizaine de nm. Cetteapproche est comparable à une échographie mais à l’échelle cellulaire. L’étude de l’adhésion et despropriétés mécaniques de plusieurs types de cellules à différents stades de maturation est abordée.Des images topographiques des zones fines (< 50 nm) d’une cellule sont également analysées. Lemicroscope développé durant cette thèse offrira la possibilité d’explorer de nouvelles pistes derecherche dans les domaines de la biologie cellulaire et des biotechnologies

An opto-acoustic microscope based on picosecond ultrasonics for single cell ultrasonography

L’adhésion et les propriétés mécaniques des cellules jouent un rôle crucial dans le fonctionnementcellulaire ainsi que dans l’apparition de maladies dégénératives. Pour mesurer ces quantités, nousavons développé dans ce travail un microscope opto-acoustique pour l’imagerie non-invasive de lamécanique de cellules individuelles avec une résolution sub-cellulaire. Ce microscope utilise latechnique d’acoustique picoseconde qui permet de générer et détecter optiquement des ondesacoustiques avec une large bande s’étendant jusqu’à 1 THz. Dans le but de reproduire lecomportement mécanique des cellules à des fréquences acoustiques supérieures à 10 GHz, uneétude sur des objets mous biomimétiques est menée dans une première partie. Les rigidité, viscositéet épaisseur de ces systèmes multicouches micrométriques sont caractérisées. Dans la deuxièmepartie de ce manuscrit, la technique d’acoustique picoseconde est employée pour imager le contactentre une cellule animale modèle et un biomatériau, ainsi que l’impédance acoustique de cette cellule.Un outil d’analyse nécessaire pour le traitement du signal acoustique est mis en place. Enfin, unmicroscope opto-acoustique opérationnel entre 10 et 100 GHz est présenté dans la dernière partie. Ilest basé sur un dispositif pompe-sonde asynchrone qui permet de produire des images acoustiquesen un temps court (4 pixels/min) avec une résolution axiale de l’ordre d’une dizaine de nm. Cetteapproche est comparable à une échographie mais à l’échelle cellulaire. L’étude de l’adhésion et despropriétés mécaniques de plusieurs types de cellules à différents stades de maturation est abordée.Des images topographiques des zones fines (< 50 nm) d’une cellule sont également analysées. Lemicroscope développé durant cette thèse offrira la possibilité d’explorer de nouvelles pistes derecherche dans les domaines de la biologie cellulaire et des biotechnologies.Adhesion and mechanical properties of cells are key players in several cellular functions and areinvolved in the development of degenerative diseases. To characterize these quantities, we developedin this work an opto-acoustic microscope for the non-invasive imaging of the mechanics of individualcells with a sub-cell resolution. This microscope uses the Picosecond Ultrasonics (PU) technique thatallows optical generation and detection of acoustic waves with a large bandwidth up to 1 THz. In orderto reproduce the mechanical behaviour of cells at acoustic frequencies greater than 10 GHz, a studyof cell-mimicking micro-objects is first considered. The rigidity, viscosity and thickness of these microlayeredstructures are characterized. In the second part of this manuscript, the PU technique isapplied for imaging the contact between a simple animal cell and a biomaterial, as well as the acousticimpedance of this cell. An essential tool for analysing the acoustic signal is developed. In the thirdpart, the opto-acoustic microscope operating between 10 and 100 GHz is finally presented. It is basedon an asynchronous pump-probe setup that allows producing acoustic images within a short time (4pixels/min) and offering an axial resolution of about 10 nm. This is similar to cell ultrasonography. Thestudy of the adhesion and of the mechanical properties of different cell types at different stages of cellmaturation is then tackled. The topographic images of thin cell regions (< 50 nm) are also analysed.The microscope implemented during this thesis should offer the possibility of exploring new avenuesin the field of cellular biology

Nanocontact Tailoring via Microlensing Enables Giant Postfabrication Mesoscopic Tuning in a Self‐Assembled Ultrasonic Metamaterial

International audienc

Designing plant-based phononic materials for the manipulation of sub-GHz acoustic waves

Plants present a versatile engineering platform to design sustainable and multifunctional materials due, in part, to their natural abundance, self-growing capacity, and functional diversity. While plant-based materials technology has started to gain momentum in photonics, robotics, and soft electronics, it has not yet met phononic materials design. In this work, we investigate the phononic behavior of micro-structured plant cells scaffolds composed of dehydrated plant cell walls. Using laser-generated acoustic waves, we measure the dispersion curves of sub-GHz surface and guided waves in these biocomposites, and reveal the presence of phononic band gaps due to their interaction with compressional and flexural local resonances of the cell wall structure. Moreover, we show that these locally resonant phononic features can be controlled by altering the phenotype of the plant cells. Our results suggest a significant potential for acoustic manipulation of MHz-GHz frequencies using bio-derived surfaces, which we anticipate can lead to a wide range of green ultrasonic devices with tailorable properties