Electrical properties of human skin: From linear recordings of exogenous electrodermal activity to non-linear memristor measurements
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- Fysisk institutt [3666]
Abstract
This thesis is all about applying an electrical voltage to human skin and measuring the corresponding electrical current. A recording (on any tissue) is non-linear when the electrical properties are affected by the applied signal itself; The measurement is linear otherwise. Non-linear measurements on human skin initiate a very new field of research. Dependent on the polarity of the applied voltage, the sweat inside the ducts is moved towards the skin surface or towards deeper skin layers. Here we confirmed that the sweat ducts are memristors (memory resistor) and found that information can actually be stored inside. If you are a forgetful person, this might be a way to store your bank pin number in the future. A second memristor can be found in the stratum corneum (the tissue in the outer layer of the skin that surrounds the sweat ducts). However, the voltage-current characteristics recorded from human skin vary largely among subjects with potential applications in Diagnostics. Further, we found that human skin can act as a frequency doubler and halve-wave rectifier. An example of linear measurements will be given as an introduction. Changes in sweating due to sympathetic nervous activity are subject of (linear) electrodermal activity (EDA) recordings. Here, the test subjects were asked to do continuous subtractions and deep breaths, to stimulate their sweat activity. By doing so, it was possible to find out that EDA recordings using the alternating current (AC) method are comparable with recordings using the direct current (DC) method.List of papers
Paper I: “Comparison between the AC and DC measurement of electrodermal activity”. O. Pabst, C. Tronstad, S. Grimnes, D. Fowles, and Ø. G. Martinsen. Psychophysiology, 54 (2017), 374–385. DOI: 10.1111/psyp.12803. The article is included in the thesis. Also available at: https://doi.org/10.1111/psyp.12803 |
Paper II: “Human Skin is a generic, non-volatile memristor”. O. Pabst, Ø. G. Martinsen, and L. Chua. The paper is included in the thesis. The results from paper II are published in four articles: 1) The non-linear electrical properties of human skin make it a generic memristor (Scientific reports DOI: 10.1038/s41598-018-34059-6) 2) Information can be stored in the human skin memristor which has non-volatile memory (Scientific reports DOI: /10.1038/s41598-019-55749-9) 3) Rectifying memristor bridge circuit realized with human skin (Journal of Electrical Bioimpedance DOI: 10.2478/joeb-2018-0023) 4) Simulation based comparison between a transversal and a tangential memristor model with a capacitance in parallel (Plos One DOI: 10.1371/journal.pone.0221533) |
Paper III: “Instrumentation, electrode choice and challenges in human skin memristor measurement”. O. Pabst, C. Tronstad, and Ø. G. Martinsen. Engineering in Medicine and Biology Society (EMBC), 2017 39th Annual International Conference of the IEEE. DOI: 10.1109/EMBC.2017.8037205. The article is not available in DUO due to publisher restrictions. The published version is available at: https://doi.org/10.1109/EMBC.2017.8037205 |
Paper IV: “Interpretation of the pinched point position in human skin memristor measurements”. O. Pabst, and Ø. G. Martinsen. EMBEC & NBC 2017: Springer, 2017. DOI: 10.1007/978-981-10-5122-7_108. The article is not available in DUO due to publisher restrictions. The published version is available at: https://doi.org/10.1007/978-981-10-5122-7_108 |