Person: Pérez García, Lucas
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First Name
Lucas
Last Name
Pérez García
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de Materiales
Area
Física Aplicada
Identifiers
18 results
Search Results
Now showing 1 - 10 of 18
Item Nanostructured gold electrodes promote neural maturation and network connectivity(Biomaterials, 2021) Dominguez-Bajo, Ana; Rosa, Juliana M.; González-Mayorga, Ankor; Rodilla González, Beatriz Loreto; Arché-Nuñez, Ana; Benayas, Esther; Ocón, Pilar; Pérez García, Lucas; Camarero, Julio; Miranda, Rodolfo; González, M. Teresa; Aguilar, Juan; Lopez-Dolado, Elisa; Serrano, María C.Progress in the clinical application of recording and stimulation devices for neural diseases is still limited, mainly because of suboptimal material engineering and unfavorable interactions with biological entities. Nanotechnology is providing upgraded designs of materials to better mimic the native extracellular environment and attain more intimate contacts with individual neurons, besides allowing for the miniaturization of the electrodes. However, little progress has been done to date on the understanding of the biological impact that such neural interfaces have on neural network maturation and functionality. In this work, we elucidate the effect of a gold (Au) highly ordered nanostructure on the morphological and functional interactions with neural cells and tissues. Alumina-templated Au nanostructured electrodes composed of parallel nanowires of 160 nm in diameter and 1.2 mu m in length (Au-NWs), with 320 nm of pitch, are designed and characterized. Equivalent non-structured Au electrodes (Au-Flat) are used for comparison. By using diverse techniques in in vitro cell cultures including live calcium imaging, we found that Au-NWs interfaced with primary neural cortical cells for up to 14 days allow neural networks growth and increase spontaneous activity and ability of neuronal synchronization, thus indicating that nanostructured features favor neuronal network. The enhancement in the number of glial cells found is hypothesized to be behind these beneficial functional effects. The in vivo effect of the implantation of these nanostructured electrodes and its potential relevance for future clinical applicability has been explored in an experimental model of rat spinal cord injury. Subacute responses to implanted Au-NWs show no overt reactive or toxic biological reactions besides those triggered by the injury itself. These results highlight the translational potential of Au-NWs electrodes for in vivo applications as neural interfaces in contact with central nervous tissues including the injured spinal cord.Item Helical surface magnetization in nanowires: the role of chirality(Nanoscale, 2020) Ruiz Gómez, Sandra; Fernández González, Claudia; Martínez, Eduardo; Raposo, Víctor; Sorrentino, Andrea; Foerster, Michael; Aballe, Lucía; Mascaraque Susunaga, Arantzazu; Ferrer, Salvador; Pérez García, LucasNanomagnetism is nowadays expanding into three dimensions, triggered by the discovery of new magnetic phenomena and their potential use in applications. This shift towards 3D structures should be accompanied by strategies and methodologies to map the tridimensional spin textures associated. We present here a combination of dichroic X-ray transmission microscopy at different angles and micromagnetic simulations allowing to determine the magnetic configuration of cylindrical nanowires. We have applied it to permalloy nanowires with equispaced chemical barriers that can act as pinning sites for domain walls. The magnetization at the core is longitudinal and generates at the surface of the wire helical magnetization. Different types of domain walls are found at the pinning sites, which respond differently to applied fields depending on the relative chirality of the adjacent domains.Item Large magnetoresistance of isolated domain walls in La_(0.7)Sr(0.3)MnO_3 nanowires(Advanced Materials, 2023) Orfila Rodríguez, Gloria; Sanchez-Manzano, David; Arora, Ashima; Cuéllar Jiménez, Fabian Andrés; Ruiz Gómez, Sandra; Rodriguez-Corvillo, Sara; López, Sandra; Peralta, Andrea; Carreira, Santiago J.; Gallego, Fernando; Tornos Castillo, Javier; Rouco Gómez, Víctor; Riquelme, Juan J.; Munuera, Carmen; Mompean, Federico J.; Garcia-Hernandez, Mar; Sefrioui Khamali, Zouhair; Villegas Hernández, Javier Eulogio; Pérez García, Lucas; Rivera Calzada, Alberto Carlos; León Yebra, Carlos; Valencia, Sergio; Santamaría Sánchez-Barriga, JacoboGeneration, manipulation, and sensing of magnetic domain walls are cornerstones in the design of efficient spintronic devices. Half-metals are amenable for this purpose as large low field magnetoresistance signals can be expected from spin accumulation at spin textures. Among half metals, La1−xSrxMnO3 (LSMO) manganites are considered as promising candidates for their robust half-metallic ground state, Curie temperature above room temperature (Tc = 360 K, for x = 1/3), and chemical stability. Yet domain wall magnetoresistance is poorly understood, with large discrepancies in the reported values and conflicting interpretation of experimental data due to the entanglement of various source of magnetoresistance, namely, spin accumulation, anisotropic magnetoresistance, and colossal magnetoresistance. In this work, the domain wall magnetoresistance is measured in LSMO cross-shape nanowires with single-domain walls nucleated across the current path. Magnetoresistance values above 10% are found to be originating at the spin accumulation caused by the mistracking effect of the spin texture of the domain wall by the conduction electrons. Fundamentally, this result shows the importance on non-adiabatic processes at spin textures despite the strong Hund coupling to the localized t2g electrons of the manganite. These large magnetoresistance values are high enough for encoding and reading magnetic bits in future oxide spintronic sensors.Item Dense strontium hexaferrite-based permanent magnet composites assisted by cold sintering process(Journal of alloys and compounds, 2022) García Martín, Eduardo; Granados Miralles, Cecilia; Ruiz Gómez, Sandra; Pérez García, Lucas; Campo, Adolfo del; Guzmán Mínguez, Jesús C.; Julián Fernández, César de; Quesada, Adrián; Fernández, José F.; Serrano, AidaThe use of rare-earth-based permanent magnets is one of the critical points for the development of the current technology. On the one hand, industry of the rare-earths is highly polluting due to the negative environmental impact of their extraction and, on the other hand, the sector is potentially dependent on China. Therefore, investigation is required both in the development of rare-earth-free permanent magnets and in sintering processes that enable their greener fabrication with attractive magnetic properties at a more competitive price. This work presents the use of a cold sintering process (CSP) followed by a post annealing at 1100 degrees C as a new way to sinter composite permanent magnets based on strontium ferrite (SFO). Composites that incorporate a percentage <= 10% of an additional magnetic phase have been prepared and the morphological, structural and magnetic properties have been evaluated after each stage of the process. CSP induces a phase transformation of SFO in the composites, which is partially recovered by the post thermal treatment improving the relative density to 92% and the magnetic response of the final magnets with a coercivity of up to 3.0 kOe. Control of the magnetic properties is possible through the composition and the grain size in the sintered magnets. These attractive results show the potential of the sintering approach as an alternative to develop modern rare-earth-free composite permanent magnets.Item Flexible metallic core–shell nanostructured electrodes for neural interfacing(Scientific Reports, 2024) Rodilla González, Beatriz Loreto; Arché-Nuñez, Ana; Ruiz-Gómez, Sandra; Domínguez-Bajo, Ana; Fernández-González, Claudia; Guillén-Colomer, Clara; González-Mayorga, Ankor; Rodríguez-Díez, Noelia; Camarero, Julio; Miranda, Rodolfo; López-Dolado, Elisa; Ocón, Pilar; Serrano, María Concepción; Pérez García, Lucas; González, M. TeresaElectrodes with nanostructured surface have emerged as promising low-impedance neural interfaces that can avoid the charge‐injection restrictions typically associated to microelectrodes. In this work, we propose a novel approximation, based on a two-step template assisted electrodeposition technique, to obtain flexible nanostructured electrodes coated with core–shell Ni–Au vertical nanowires. These nanowires benefit from biocompatibility of the Au shell exposed to the environment and the mechanical properties of Ni that allow for nanowires longer and more homogeneous in length than their only-Au counterparts. The nanostructured electrodes show impedance values, measured by electrochemical impedance spectroscopy (EIS), at least 9 times lower than those of flat reference electrodes. This ratio is in good accordance with the increased effective surface area determined both from SEM images and cyclic voltammetry measurements, evidencing that only Au is exposed to the medium. The observed EIS profile evolution of Ni–Au electrodes over 7 days were very close to those of Au electrodes and differently from Ni ones. Finally, the morphology, viability and neuronal differentiation of rat embryonic cortical cells cultured on Ni–Au NW electrodes were found to besimilar to those on control (glass) substrates and Au NW electrodes, accompanied by a lower glial cell differentiation. This positive in-vitro neural cell behavior encourages further investigation to explore the tissue responses that the implantation of these nanostructured electrodes might elicit in healthy (damaged) neural tissues in vivo, with special emphasis on eventual tissue encapsulation.Item Direct x-ray detection of the spin hall effect in CuBi(Physical review X, 2022) Ruiz Gómez, Sandra; Guerrero, Rubén; Khaliq, Muhammad W; Fernández González, Claudia; Prat, Jordi; Valera, Andrés; Finizio, Simone; Perna, Paolo; Camarero, Julio; Pérez García, Lucas; Aballe, Lucía; Foerster, MichaelThe spin Hall effect and the inverse spin Hall effect are important spin-charge conversion mechanisms. The direct spin Hall effect induces a surface spin accumulation from a transverse charge current due to spin-orbit coupling even in nonmagnetic conductors. However, most detection schemes involve additional interfaces, leading to large scattering in reported data. Here we perform interface-free x-ray spectroscopy measurements at the Cu L_(3;2) absorption edges of highly Bi-doped Cu (Cu_(95)Bi_5). The detected x-ray magnetic circular dichroism signal corresponds to an induced magnetic moment of (2.2 + 0.5) x 10^(-12) mu(B) A^(-1) cm^(2) per Cu atom averaged over the probing depth, which is of the same order of magnitude as found for Pt measured by magneto-optics. The results highlight the importance of interface-free measurements to assess material parameters and the potential of CuBi for spin-charge conversion applications.Item Scaling up the production of electrodeposited nanowires: a roadmap towards applications(Nanomaterials, 2021) Fernández González, Claudia; Guzmán Mínguez, Jesús C.; Guedeja-Marrón Gil, Alejandra; García Martín, Eduardo; Foerster, Michael; Niño, Miguel Ángel; Aballe, Lucía; Quesada, Adrian; Pérez García, Lucas; Ruiz Gómez, SandraThe use of metallic nanowires is mostly reduced to scientific areas where a small quantity of nanostructures are needed. In order to broaden the applicability of these nanomaterials, it is necessary to establish novel synthesis protocols that provide a larger amount of nanowires than the conventional laboratory fabrication processes at a more competitive cost. In this work, we propose several modifications to the conventional electrochemical synthesis of nanowires in order to increase the production with considerably reduced production time and cost. To that end, we use a soft anodization procedure of recycled aluminum at room temperature to produce the alumina templates, followed by galvanostatic growth of CoFe nanowires. We studied their morphology, composition and magnetic configuration, and found that their properties are very similar to those obtained by conventional methods.Item Electrodeposited magnetic nanowires with radial modulation of composition(Nanomaterials, 2022) Fernández González, Claudia; Guedeja-Marrón Gil, Alejandra; Rodilla González, Beatriz Loreto; Arché Nuñez, Ana; Corcuera, Rubén; Lucas, Irene; González, María Teresa; Varela del Arco, María; Presa Muñoz del Toro, Patricia de la; Aballe, Lucía; Pérez García, Lucas; Ruíz Gómez, SandraIn the last few years, magnetic nanowires have gained attention due to their potential implementation as building blocks in spintronics applications and, in particular, in domain-wall- based devices. In these devices, the control of the magnetic properties is a must. Cylindrical magnetic nanowires can be synthesized rather easily by electrodeposition and the control of their magnetic properties can be achieved by modulating the composition of the nanowire along the axial direction. In this work, we report the possibility of introducing changes in the composition along the radial direction, increasing the degrees of freedom to harness the magnetization. In particular, we report the synthesis, using template-assisted deposition, of FeNi (or Co) magnetic nanowires, coated with a Au/Co (Au/FeNi) bilayer. The diameter of the nanowire as well as the thickness of both layers can be tuned at will. In addition to a detailed structural characterization, we report a preliminary study on the magnetic properties, establishing the role of each layer in the global collective behavior of the system.Item Micromagnetics of magnetic chemical modulations in soft-magnetic cylindrical nanowires(Physical review B, 2022) Álvaro Gómez, Laura; Ruiz Gómez, S.; Fernández González, Claudia; Schobitz, M.; Mille, N.; Hurst, J.; Tiwari, D.; De Riz, A.; Andersen, I. M.; Bachmann, J.; Cagnon, L.; Foerster, M.; Belkhou, R.; Toussaint, J-C; Thirion, C.; Masseboeuf, A.; Gusakova, D.; Pérez García, Lucas; Fruchart, O.We analyze the micromagnetics of short longitudinal modulations of a high-magnetization material in cylindrical nanowires made of a soft-magnetic material of lower magnetization such as permalloy, combining magnetic microscopy, analytical modeling, and micromagnetic simulations. The mismatch of magnetization induces curling of magnetization around the axis in the modulations, in an attempt to screen the interfacial magnetic charges. The curling angle increases with modulation length, until a plateau is reached with nearly full charge screening for a specific length scale delta(mod), larger than the dipolar exchange length of any of the two materials. The curling circulation can be switched by the Oersted field arising from a charge current with typical magnitude 10(12) A/m(2) for a diameter of similar to 100 nm, and reaching a maximum for delta(mod).Item Polystyrene nanopillars with inbuilt carbon nanotubes enable synaptic modulation and stimulation in interfaced neuronal networks(Advanced materials interfaces, 2021) Calaresu, Ivo; Hernández, Jaime; Rauti, Rossana; Rodilla, Beatriz L.; Arché-Núñez, Ana; Pérez García, Lucas; Camarero, Julio; Miranda, Rodolfo; González, M. Teresa; Rodríguez, Isabel; Scaini, Denis; Ballerini, LauraThe use of nanostructured materials and nanosized-topographies has the potential to impact the performance of implantable biodevices, including neural interfaces, enhancing their sensitivity and selectivity, while reducing tissue reactivity. As a result, current trends in biosensor technology require the effective ability to improve devices with controlled nanostructures. Nanoimprint lithography to pattern surfaces with high-density and high aspect ratio nanopillars (NPs) made of polystyrene (PS-NP, insulating), or of a polystyrene/carbon-nanotube nanocomposite (PS-CNT-NP, electrically conductive) are exploited. Both substrates are challenged with cultured primary neurons. They are demonstrated to support the development of suspended synaptic networks at the NPs' interfaces characterized by a reduction in proliferating neuroglia, and a boost in neuronal emergent electrical activity when compared to flat controls. The authors successfully exploit their conductive PS-CNT-NPs to stimulate cultured cells electrically. The ability of both nanostructured surfaces to interface tissue explants isolated from the mouse spinal cord is then tested. The integration of the neuronal circuits with the NP topology, the suspended nature of the cultured networks, the reduced neuroglia formation, and the higher network activity together with the ability to deliver electrical stimuli via PS-CNT-NP reveal such platforms as promising designs to implement on neuro-prosthetic or neurostimulation devices.