Giant magnetoresistance based sensors for local magnetic detection of neuronal currents Laure Caruso To cite this version: Laure Caruso. Giant magnetoresistance based sensors for local magnetic detection of neuronal cur- rents. Medical Physics [physics.med-ph]. Université Pierre et Marie Curie - Paris VI, 2015. English. NNT : 2015PA066272. tel-01241867 HAL Id: tel-01241867 https://tel.archives-ouvertes.fr/tel-01241867 Submitted on 11 Dec 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Université Pierre et Marie Curie Doctoral school ED PIF CEA Saclay, DSM/IRAMIS/SPEC/LNO Giant magnetoresistance based sensors for local magnetic detection of neuronal currents Par Laure Caruso Thèse de doctorat de Physique Dirigée par Myriam Pannetier-Lecoeur Présentée et soutenue publiquement le 21/07/2015 Devant un jury composé de : Professor Risto Ilmoniemi : reviewer Professor Michel Hehn : reviewer Susana de Freitas Thierry Bal Régis Lambert Denis Schwartz Contents 1 Neurophysiology 8 1.1 Biology of neurons . 8 1.1.1 Structure of neurons . 8 1.1.1.1 From brain to neuronal cells . 8 1.1.1.2 Neuron morphology . 9 1.1.2 Function of neurons . 9 1.1.2.1 Ions flux across the neural cell membrane . 9 1.1.2.2 Neurotransmission . 10 1.1.2.3 Action Potential . 11 1.1.2.4 Local Field Potential . 12 1.2 Electrophysiology . 13 1.2.1 Macroscopic scale . 13 1.2.1.1 Electroencephalogram - EEG . 13 1.2.1.2 Electrocorticography - ECoG . 14 1.2.2 Mesoscopic scale . 14 1.2.2.1 Extracellular recordings . 15 1.2.2.2 Optical techniques . 15 1.2.3 Microscopic scale . 17 1.2.3.1 Intracellular recordings . 17 1.3 Magnetophysiology . 19 1.3.1 Brain scale: magnetoencephalography . 19 1.3.2 Local measurements . 20 1.3.3 Magnetic field created by neurons . 21 1.3.3.1 A very simple model of a single neuron . 21 1.3.3.2 More sophisticated models of a single neuron . 22 1.3.3.3 Assembly of neurons . 25 1 CONTENTS 2 1.3.3.4 Analysis of the models . 28 1.3.4 Conclusion . 29 2 Magnetic sensors 30 2.1 Magnetic sensors for biomedical applications . 30 2.1.1 Magnetic field amplitudes . 30 2.1.2 Magnetic sensors for biomedical applications . 31 2.1.2.1 SQUIDs . 32 2.1.2.2 Atomic magnetometer . 33 2.2 Magnetoresistive sensors . 35 2.2.1 Spin electronics . 35 2.2.2 Spin Valve -Giant MagnetoResistance . 36 2.2.2.1 Sensor Magneto-Resistance (MR) ratio and sensitivity . 38 2.2.3 SV sensor . 39 2.2.3.1 Sensor shape . 39 2.2.3.2 Contacts . 41 2.3 Noise sources . 42 2.3.1 Detectivity . 43 2.3.2 Thermal noise (Johnson noise) . 44 2.3.3 1/f noise (Flicker noise) . 45 2.3.4 Random Telegraphic Noise (RTN) . 45 2.3.5 Magnetic noise . 46 2.4 Conclusion . 47 3 Magnetrodes 48 3.1 Probes fabrication . 48 3.1.1 Sharp probe . 50 3.1.1.1 Probe design . 50 3.1.1.2 Sensor design . 53 3.1.1.3 Probes microfabrication . 53 3.1.1.4 Dry etching . 56 3.1.1.5 Deposition techniques . 57 3.1.1.6 Final probe shape . 60 3.1.2 Planar probes . 63 3.1.2.1 Probe design . 63 CONTENTS 3 3.1.2.2 Planar probe fabrication . 66 3.1.3 Probes packaging . 66 3.1.3.1 Connection . 66 3.1.3.2 Packaging . 67 3.2 Measurement methods and probe characterization . 68 3.2.1 Magneto transport characterization methods . 68 3.2.1.1 R(H) transfer curve . 68 3.2.1.2 Response . 70 3.2.1.3 Noise . 70 3.2.2 Measurement methods . 71 3.2.2.1 DC measurement . 72 3.2.2.2 Capacitive coupling . 73 3.2.2.3 AC measurement (frequency demodulation) . 73 3.2.2.4 Sensitivity measurements . 76 3.2.3 Probes characterization . 79 3.2.3.1 Planar probes . 79 3.2.3.2 Sharp probes . 81 3.3 Phantom . 86 3.3.1 Setup . 86 3.3.2 Results . 88 3.4 Conclusions . 89 4 In vitro recordings 92 4.1 Muscle experiment . 92 4.1.1 Context and Objectives . 92 4.1.1.1 Nerve-muscle junction physiology . 92 4.1.1.2 Magnetic response modeling . 93 4.1.1.3 Objectives . 95 4.1.2 Experiment / Methods . 97 4.1.3 Magnetic recordings . 99 4.1.3.1 Magnetic sensors . 99 4.1.3.2 Magnetic signal recordings . 100 4.1.3.3 Geometry study . 104 4.1.3.4 Pharmacology . 106 4.1.3.5 Tetanus . 107 CONTENTS 4 4.1.3.6 Artefacts . 108 4.1.3.7 Signal-to-noise . 109 4.1.4 Electrophysiology recordings . 110 4.1.5 Modeling . 113 4.1.6 Discussion . 115 4.2 Hippocampal slices experiment . 115 4.2.1 Context and Objectives . 115 4.2.1.1 Hippocampus physiology . 115 4.2.1.2 Objectives . 116 4.2.1.3 Simulation . 118 4.2.1.4 Slice experiments . 121 4.2.1.5 Magnetic recordings with sharp probes . 124 4.2.1.6 Conclusion . 126 5 In vivo recordings 128 5.1 Objectives . 128 5.2 Experiments / Methods . 131 5.2.1 Sensors . 131 5.2.1.1 Planar sensor . 131 5.2.1.2 Sharp sensors . 132 5.2.2 Experimental protocol . 134 5.3 Results . 135 5.3.1 AC mode . 136 5.3.2 DC mode . 140 5.3.3 Control experiments . 141 5.3.3.1 I=0 . 141 5.3.3.2 Tangential direction . ..