The magnetoelectrochemical switch

In the field of spintronics, the archetype solid-state two-terminal device is the spin valve, where the resistance is controlled by the magnetization configuration. We show here how this concept of spin-dependent switch can be extended to magnetic electrodes in solution, by magnetic control of their chemical environment. Appropriate nanoscale design allows a huge enhancement of the magnetic force field experienced by paramagnetic molecular species in solutions, which changes between repulsive and attractive on changing the electrodes' magnetic orientations. Specifically, the field gradient force created within a sub-100-nm-sized nanogap separating two magnetic electrodes can be reversed by changing the orientation of the electrodes' magnetization relative to the current flowing between the electrodes. This can result in a breaking or making of an electric nanocontact, with a change of resistance by a factor of up to 103. The results reveal how an external field can impact chemical equilibrium in the vicinity of nanoscale magnetic circuits

Mode III cleavage of a coin-shaped titanium implant in bone: effect of friction and crack propagation

International audienceEndosseous cementless implants are widely used in orthopaedic, maxillofacial and oral surgery. However, failures are still observed and remain difficult to anticipate as remodelling phenomena at the bone-implant interface are poorly understood. The assessment of the biomechanical strength of the bone-implant interface may improve the understanding of the osseointegration process. An experimental approach based on a mode III cleavage mechanical device aims at understanding the behavior of a planar bone-implant interface submitted to torsional loading. To do so, coin-shaped titanium implants were inserted on the tibiae of a New Zealand White rabbit for seven weeks. After sacrifice, mode III cleavage experiments were performed on bone samples. An analytical model was developed to understand the debonding process of the bone-implant interface. The model allowed to assess the values of different parameters related to bone tissue at the vicinity of the implant with the additional assumption that bone adhesion occurs over around 70% of the implant surface, which is confirmed by microscopy images. The approach allows to estimate different quantities related to the bone-implant interface such as: torsional stiffness (around 20.5 N.m.rad-1), shear modulus (around 240 MPa), maximal torsional loading (around 0.056 N.m), mode III fracture energy (around 77.5 N.m-1) and stress intensity factor (0.27 MPa.m1/2). This study paves the way for the use of mode III cleavage testing for the investigation of torsional loading strength of the bone-implant interface, which might help for the development and optimization of implant biomaterial, surface treatment and medical treatment investigations

New molecules for molecular electronics and their applications in spintronics

L'électronique moléculaire est un domaine d'étude visant à caractériser le transport du courant au travers des systèmes organiques (polymères, couche moléculaire, molécule unique) disposés entre deux électrodes métalliques. Si les électrodes sont des métaMolecular electronic relates to the study of electrical transport through organic systems (polymers, molecular monolayer, single molecule) trapped between two metallic electrodes. If the electrodes are made of ferromagnetic materials, one can talk about

USE OF ZWITTERIONIC MOLECULES FOR FORMING A HOLE OR ELECTRON TRANSPORT LAYER

The invention relates to the use of zwitterionic molecules for forming a hole or electron transport layer. The preferred zwitterionic molecules of the invention are derivatives of p-benzoquinonemonoimines. The invention is useful in the field of electronic devices in particular

Macromolecular Additives to Turn a Thermoplastic Elastomer into a Self-Healing Material

International audienceSelf-healing allows increasing the service life of materials by overcoming some issues caused by mechanical failures. We propose a new concept to bring room temperature selfhealing properties to thermoplastic elastomers. A macromolecular additive whose interacting units can interfere with the hard segments of the thermoplastic elastomer accelerates chain dynamics and brings self-healing properties to the composite material with a limited detrimental effect on mechanical properties. By applying this concept to silicone-based elastomers, we have obtained an autonomously self-healing material with a relatively high elastic modulus for this type of elastomers

Hydrogen bonded silicone rubber: A new additive improving self-healing

256th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nanoscience, Nanotechnology and Beyond, Boston, MA, AUG 19-23, 2018International audienc

Ultrafast Remote Healing of Magneto-Responsive Thermoplastic Elastomer-Based Nanocomposites

International audienceWe describe herein, a general, efficient, and scalable process to design magneto-responsive thermoplastic elastomerbased (nano)composites that can be repeatedly healed in a few tens of seconds by triggering polymer melting upon exposure to a high-frequency magnetic field. Three series of composites loaded with 1−15 vol % of Fe3O4 nanoparticles, Fe nanoparticles, or Fe microparticles were produced and characterized in depth with the aim to identify the physical properties required for two applications: (1) material healing, which we evaluate through the rewelding of precut samples and subsequent tensile tests, and (2) surface smoothening of 3D-printed objects, serving to remove superficial defects and improve their appearance. The optimal formulation consisting of a composite reinforced with 5 vol % of Fe nanoparticles ensures a high ability to heat while keeping a low viscosity in the molten state being ideal for polymer processing

Altering the Static Dipole on Surfaces through Chemistry: Molecular Films of Zwitterionic Quinonoids

The adsorption of molecular films made of small molecules with a large intrinsic electrical dipole has been explored. The data indicate that such dipolar molecules may be used for altering the interface dipole screening at the metal electrode interface in organic electronics. More specifically, we have investigated the surface electronic spectroscopic properties of zwitterionic molecules containing 12π electrons of the <i>p</i>-benzoquinonemonoimine type, C₆H₂(<u>···</u>NHR)₂(<u>···</u>O)₂ (R = H (<b>1</b>), <i>n</i>-C₄H₉ (<b>2</b>), C₃H₆–S–CH₃ (<b>3</b>), C₃H₆–O–CH₃ (<b>4</b>), CH₂–C₆H₅ (<b>5</b>)), adsorbed on Au. These molecules are stable zwitterions by virtue of the meta positions occupied by the nitrogen and oxygen substituents on the central ring, respectively. The structures of <b>2</b>–<b>4</b> have been determined by single crystal X-ray diffraction and indicate that in these molecules, two chemically connected but electronically not conjugated 6π electron subunits are present, which explains their strong dipolar character. We systematically observed that homogeneous molecular films with thickness as small as 1 nm were formed on Au, which fully cover the surface, even for a variety of R substituents. Preferential adsorption toward the patterned gold areas on SiO₂ substrates was found with <b>4</b>. Optimum self-assembling of <b>2</b> and <b>5</b> results in ordered close packed films, which exhibit n-type character, based on the position of the Fermi level close to the conduction band minimum, suggesting high conductivity properties. This new type of self-assembled molecular films offers interesting possibilities for engineering metal–organic interfaces, of critical importance for organic electronics