Development of Capacitive-Type Sensors by Electrochemical Anodization: Humidity and Touch Sensing Applications

This work describes the development of a capacitive-type sensor created from nanoporous anodic aluminium oxide (NP-AAO) prepared by the one-step anodization method conducted in potentiostatic mode and performed in a low-cost homemade system. A series of samples were prepared via an anodization campa...

Descripción completa

Guardado en:

Detalles Bibliográficos
Autores principales:	Joaquim O. Carneiro, Artur Ribeiro, Filipe Miranda, Iran Rocha Segundo, Salmon Landi, Vasco Teixeira, Manuel F. M. Costa
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	capacitive-type sensor sensitivity anodization nanoporous anodic alumina Chemical technology TP1-1185
Acceso en línea:	https://doaj.org/article/8cfdbbd78dad43039be1f8ddaa7aa480
Etiquetas:	Agregar Etiqueta Sin Etiquetas, Sea el primero en etiquetar este registro!

id	oai:doaj.org-article:8cfdbbd78dad43039be1f8ddaa7aa480
record_format	dspace
spelling	oai:doaj.org-article:8cfdbbd78dad43039be1f8ddaa7aa4802021-11-11T19:16:00ZDevelopment of Capacitive-Type Sensors by Electrochemical Anodization: Humidity and Touch Sensing Applications10.3390/s212173171424-8220https://doaj.org/article/8cfdbbd78dad43039be1f8ddaa7aa4802021-11-01T00:00:00Zhttps://www.mdpi.com/1424-8220/21/21/7317https://doaj.org/toc/1424-8220This work describes the development of a capacitive-type sensor created from nanoporous anodic aluminium oxide (NP-AAO) prepared by the one-step anodization method conducted in potentiostatic mode and performed in a low-cost homemade system. A series of samples were prepared via an anodization campaign carried out on different acid electrolytes, in which the anodization parameters were adjusted to investigate the effect of pore size and porosity on the capacitive sensing performance. Two sensor test cases are investigated. The first case explores the use of highly uniform NP-AAO structures for humidity sensing applications while the second analyses the use of NP-AAO as a capacitive touch sensor for biological applications, namely, to detect the presence of small “objects” such as bacterial colonies of <i>Escherichia Coli.</i> A mathematical model based on equivalent electrical circuits was developed to evaluate the effect of humidity condensation (inside the pores) on the sensor capacitance and also to estimate the capacitance change of the sensor due to pore blocking by the presence of a certain number of bacterial microorganisms. Regarding the humidity sensing test cases, it was found that the sensitivity of the sensor fabricated in a phosphoric acid solution reaches up to 39 (pF/RH%), which is almost three times higher than the sensor fabricated in oxalic acid and about eight times higher than the sensor fabricated in sulfuric acid. Its improved sensitivity is explained in terms of the pore size effect on the mean free path and the loss of Brownian energy of the water vapour molecules. Concerning the touch sensing test case, it is demonstrated that the NP-AAO structures can be used as capacitive touch sensors because the magnitude of the capacitance change directly depends on the number of bacteria that cover the nanopores; the fraction of the electrode area activated by bacterial pore blocking is about 4.4% and 30.2% for B1 (<i>E. Coli</i> OD<sub>600nm</sub> = 0.1) and B2 (<i>E. Coli</i> OD<sub>600nm</sub> = 1) sensors, respectively.Joaquim O. CarneiroArtur RibeiroFilipe MirandaIran Rocha SegundoSalmon LandiVasco TeixeiraManuel F. M. CostaMDPI AGarticlecapacitive-type sensorsensitivityanodizationnanoporous anodic aluminaChemical technologyTP1-1185ENSensors, Vol 21, Iss 7317, p 7317 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	capacitive-type sensor sensitivity anodization nanoporous anodic alumina Chemical technology TP1-1185
spellingShingle	capacitive-type sensor sensitivity anodization nanoporous anodic alumina Chemical technology TP1-1185 Joaquim O. Carneiro Artur Ribeiro Filipe Miranda Iran Rocha Segundo Salmon Landi Vasco Teixeira Manuel F. M. Costa Development of Capacitive-Type Sensors by Electrochemical Anodization: Humidity and Touch Sensing Applications
description	This work describes the development of a capacitive-type sensor created from nanoporous anodic aluminium oxide (NP-AAO) prepared by the one-step anodization method conducted in potentiostatic mode and performed in a low-cost homemade system. A series of samples were prepared via an anodization campaign carried out on different acid electrolytes, in which the anodization parameters were adjusted to investigate the effect of pore size and porosity on the capacitive sensing performance. Two sensor test cases are investigated. The first case explores the use of highly uniform NP-AAO structures for humidity sensing applications while the second analyses the use of NP-AAO as a capacitive touch sensor for biological applications, namely, to detect the presence of small “objects” such as bacterial colonies of <i>Escherichia Coli.</i> A mathematical model based on equivalent electrical circuits was developed to evaluate the effect of humidity condensation (inside the pores) on the sensor capacitance and also to estimate the capacitance change of the sensor due to pore blocking by the presence of a certain number of bacterial microorganisms. Regarding the humidity sensing test cases, it was found that the sensitivity of the sensor fabricated in a phosphoric acid solution reaches up to 39 (pF/RH%), which is almost three times higher than the sensor fabricated in oxalic acid and about eight times higher than the sensor fabricated in sulfuric acid. Its improved sensitivity is explained in terms of the pore size effect on the mean free path and the loss of Brownian energy of the water vapour molecules. Concerning the touch sensing test case, it is demonstrated that the NP-AAO structures can be used as capacitive touch sensors because the magnitude of the capacitance change directly depends on the number of bacteria that cover the nanopores; the fraction of the electrode area activated by bacterial pore blocking is about 4.4% and 30.2% for B1 (<i>E. Coli</i> OD<sub>600nm</sub> = 0.1) and B2 (<i>E. Coli</i> OD<sub>600nm</sub> = 1) sensors, respectively.
format	article
author	Joaquim O. Carneiro Artur Ribeiro Filipe Miranda Iran Rocha Segundo Salmon Landi Vasco Teixeira Manuel F. M. Costa
author_facet	Joaquim O. Carneiro Artur Ribeiro Filipe Miranda Iran Rocha Segundo Salmon Landi Vasco Teixeira Manuel F. M. Costa
author_sort	Joaquim O. Carneiro
title	Development of Capacitive-Type Sensors by Electrochemical Anodization: Humidity and Touch Sensing Applications
title_short	Development of Capacitive-Type Sensors by Electrochemical Anodization: Humidity and Touch Sensing Applications
title_full	Development of Capacitive-Type Sensors by Electrochemical Anodization: Humidity and Touch Sensing Applications
title_fullStr	Development of Capacitive-Type Sensors by Electrochemical Anodization: Humidity and Touch Sensing Applications
title_full_unstemmed	Development of Capacitive-Type Sensors by Electrochemical Anodization: Humidity and Touch Sensing Applications
title_sort	development of capacitive-type sensors by electrochemical anodization: humidity and touch sensing applications
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/8cfdbbd78dad43039be1f8ddaa7aa480
work_keys_str_mv	AT joaquimocarneiro developmentofcapacitivetypesensorsbyelectrochemicalanodizationhumidityandtouchsensingapplications AT arturribeiro developmentofcapacitivetypesensorsbyelectrochemicalanodizationhumidityandtouchsensingapplications AT filipemiranda developmentofcapacitivetypesensorsbyelectrochemicalanodizationhumidityandtouchsensingapplications AT iranrochasegundo developmentofcapacitivetypesensorsbyelectrochemicalanodizationhumidityandtouchsensingapplications AT salmonlandi developmentofcapacitivetypesensorsbyelectrochemicalanodizationhumidityandtouchsensingapplications AT vascoteixeira developmentofcapacitivetypesensorsbyelectrochemicalanodizationhumidityandtouchsensingapplications AT manuelfmcosta developmentofcapacitivetypesensorsbyelectrochemicalanodizationhumidityandtouchsensingapplications
_version_	1718431597072482304

Development of Capacitive-Type Sensors by Electrochemical Anodization: Humidity and Touch Sensing Applications

Ejemplares similares