79 research outputs found
A 2-D micro-magnetic neuro-stimulation platform
No full textThe aim of this thesis is the development of a novel in-vitro neuro-stimulation tool based on the micro-scale implementation of the transcranial magnetic stimulation (TMS) principle. The project involves the design, fabrication and testing of single coil geometries and a two dimensional array of micro-coils for establishing spatio-temporal magnetic flux profiles. The proposed device can induce a localised electric field in the vicinity of the coils that can instigate the stimulation of single or multiple neurons in vitro. The first steps of this project covered the investigation of all the parameters that affect the efficiency of a micro-coil structure, in an attempt to achieve an induced electric field above the stimulation threshold of a neuron (e.g. spatial derivative electric field intensity: ∂Ex/∂x>11kV/m2 [1]). The investigation is based on a parametric study with COMSOL Multiphysics simulation software, while for the design of the structure further experimental limitations were taken into account. The fabrication steps for the development of the micro-coils include two photolithographic steps while the further increase of micro-coils’ thickness was achieved with electroplating. The packaging, the bio-compatible encapsulation with Parylene-C and the functionalization of the material, in terms of hydrophilicity, are also presented and complete the platform prototyping. The micro-coils are characterized electrically with an impedance frequency sweep while a further monitoring of their electromagnetic behaviour was performed with magnetic nanoparticles trapping and inductive measurements between different coils in the same array. Their ability to stimulate magnetically neural cells was evaluated firstly with a phantom gel with electric properties (electrical permittivity and conductivity) similar to neural tissue, with the use of bio-oriented simulations with NEURON software + COMSOL and with biological validation in vitro. Finally, the main challenge of this method is to define the limits of safe operation of the micro-inductors prior to their failure due to Joule heating and electromigration phenomena. In this direction, an electrothermal study was performed to define the maximum current capacity that could safely hold
Magnetic stimulation in the microscale: the development of a 6x6 array of micro-coils for stimulation of excitable cells in vitro
No full textIn this study we present the development of a prototype device, designed for micro-magnetic stimulation of excitable cells in vitro. Each platform consists of a 6x6 two-dimensional array of micro-coils, in an attempt to achieve highly localised magnetic flux patterns. The coils are fabricated with standard micro-fabrication techniques, including steps of photolithography, dry etching and electroplating. The further interfacing of the micro-magnetic chip into a biocompatible platform is also described. The samples are characterised electrically, while a finite element method simulation study is performed and reveals a 141mV-strong electric potential induced in the vicinity of a micro-coil. Since applications in neuronal cells is our primary focus, modelling with NEURON software is used for demonstrating the capability of the platform to activate adjacent cells. Finally, an experimental validation of the proof of concept is performed with the measurement of induced current into a custom-made phantom gel that shows similar electric properties with brain tissue
Electrothermal deterioration factors in gold planar inductors designed for microscale bio-applications
No full textIn this study, we present the fabrication of wafer level micro-inductors, designed for non invasive neuro-stimulation in vitro, along with an electrothermal study testing the influence of thermal phenomena to their performance. The electric performance of all micro-scale electromagnetic components is hampered by two dominant factors: Joule heating and electromigration. The scope of the study is to evaluate how these phenomena change the electric behaviour of the samples during activation. We experimentally define the safe area of operation across six types of samples with different geometric characteristics and we extract useful information for the reliability of the samples by comparing their median failure times. Our findings present the activation restrictions which should be taken into account in order to avoid the thermal degradation of the components, while at the same time could be used as design guidelines for similar geometries
Dataset for Magnetic stimulation in the microscale: the development of a 6x6 array of micro-coils for stimulation of excitable cells in vitro
No full textDatasets used in figures of the article named "Magnetic stimulation in the microscale: the development of a 6x6 array of micro-coils for stimulation of excitable cells in vitro" submitted in Biomedical Physics and Engineering Express.</span
Dataset for Electrothermal deterioration factors in gold planar inductors designed for microscale bio-applications
No full textDatasets used in figures of the article "Electrothermal deterioration factors in gold planar inductors designed for microscale bio-applications" in Microelectronic Engineering journal. DOI:10.1016/j.mee.2018.05.006</span
The subject of home economics in the present day school community and the local community
No full textIs it over yet? Verbal aspect in heritage Greek, Russian and Turkish
No full textVasiliki Rizou (Humboldt-Universität zu Berlin), Maria Martynova (Humboldt-Universität zu Berlin), Onur
Özsoy (ZAS), Luka Szucsich (Humboldt-Universität zu Berlin), Artemis Alexiadou (Humboldt-Universität zu
Berlin, ZAS) and Natalia Gagarina (Humboldt-Universität zu Berlin, ZAS
Is it over yet? Verbal aspect in heritage Greek, Russian and Turkish
No full textVasiliki Rizou (Humboldt-Universität zu Berlin), Maria Martynova (Humboldt-Universität zu Berlin), Onur
Özsoy (ZAS), Luka Szucsich (Humboldt-Universität zu Berlin), Artemis Alexiadou (Humboldt-Universität zu
Berlin, ZAS) and Natalia Gagarina (Humboldt-Universität zu Berlin, ZAS
Adolescents' soft drinks consumption in family environment: a case study in Northern Greece
No full text- …
