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Welden R, Das A, Krause S, Schöning MJ, Wagner PH, Wagner T. Actively Driven Light-Addressable Sensor/Actuator System for Automated pH Control for the Integration in Lab-On-A-Chip (LoC) Platforms. ACS Sens 2024; 9:1533-1544. [PMID: 38445576 DOI: 10.1021/acssensors.3c02712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2024]
Abstract
The miniaturization of microfluidic systems usually comes at the cost of more difficult integration of sensors and actuators inside the channel. As an alternative, this work demonstrates the embedding of semiconductor-based sensor and actuator technologies that can be spatially and temporally controlled from outside the channel using light. The first element is a light-addressable potentiometric sensor, consisting of an Al/Si/SiO2/Si3N4 structure, that can measure pH changes at the Si3N4/electrolyte interface. The pH value is a crucial factor in biological and chemical systems, and besides measuring, it is often important to bring the system out of equilibrium or to adjust and control precisely the surrounding medium. This can be done photoelectrocatalytically by utilizing light-addressable electrodes. These consist of a glass/SnO2:F/TiO2 structure, whereby direct charge transfer between the TiO2 and the electrolyte leads to a pH change upon irradiation. To complement the advantages of both, we integrated a light-addressable sensor with a pH sensitivity of 41.5 mV·pH-1 and a light-addressable electrode into a microfluidic setup. Here, we demonstrated a simultaneous operation with the ability to generate and record pH gradients inside a channel under static and dynamic flow conditions. The results show that dependent on the light-addressable electrode (LAE)-illumination conditions, pH changes up to ΔpH of 2.75 and of 3.52 under static and dynamic conditions, respectively, were spatially monitored by the light-addressable potentiometric sensor. After flushing with fresh buffer solution, the pH returned to its initial value. Depending on the LAE illumination, pH gradients with a maximum pH change of ΔpH of 1.42 were tailored perpendicular to the flow direction. In a final experiment, synchronous LAE illumination led to a stepwise increase in the pH inside the channel.
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Affiliation(s)
- Rene Welden
- Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Heinrich-Mußmann-Str. 1, Jülich 52428, Germany
- Laboratory for Soft Matter and Biophysics, KU Leuven, Celestijnenlaan 200D, Leuven 3001, Belgium
| | - Anirban Das
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, U.K
| | - Steffi Krause
- School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, U.K
| | - Michael J Schöning
- Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Heinrich-Mußmann-Str. 1, Jülich 52428, Germany
- Institute of Biological Information Processing (IBI-3), Forschungszentrum Jülich GmbH, Jülich 52428, Germany
| | - Patrick H Wagner
- Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Heinrich-Mußmann-Str. 1, Jülich 52428, Germany
- Laboratory for Soft Matter and Biophysics, KU Leuven, Celestijnenlaan 200D, Leuven 3001, Belgium
| | - Torsten Wagner
- Institute of Nano- and Biotechnologies (INB), Aachen University of Applied Sciences, Heinrich-Mußmann-Str. 1, Jülich 52428, Germany
- Institute of Biological Information Processing (IBI-3), Forschungszentrum Jülich GmbH, Jülich 52428, Germany
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Patiño Cárdenas J, Encinas A, Ramírez Villegas R, de la Torre Medina J. Control of the asymmetric growth of nanowire arrays with gradient profiles. RSC Adv 2021; 11:25892-25900. [PMID: 35479484 PMCID: PMC9037112 DOI: 10.1039/d1ra04198c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Accepted: 07/18/2021] [Indexed: 11/22/2022] Open
Abstract
A novel electrochemical methodology for the growth of arrays of Ni and Co nanowires (NWs) with linear and non-linear varying micro-height gradient profiles (μHGPs), has been developed. The growth mechanism of these microstructures consists of a three-dimensional growth originating from the allowed electrical contact between the electrolyte and the edges of the cathode at the bottom side of porous alumina membranes. It has been shown that the morphology of these microstructures strongly depends on electrodeposition parameters like the cation material and concentration and the reduction potential. At constant reduction potentials, linear Ni μHGPs with trapezoid-like geometry are obtained, whereas deviations from this simple morphology are observed for Co μHGPs. In this regime, the μHGPs average inclination angle decreases for more negative reduction potential values, leading as a result to more laterally extended microstructures. Besides, more complex morphologies have been obtained by varying the reduction potential using a simple power function of time. Using this strategy allows us to accelerate or decelerate the reduction potential in order to change the μHGPs morphology, so to obtain convex- or concave-like profiles. This methodology is a novel and reliable strategy to synthesize μHGPs into porous alumina membranes with controlled and well-defined morphologies. Furthermore, the synthesized low dimensional asymmetrically loaded nanowired substrates with μHGPs are interesting for their application in micro-antennas for localized electromagnetic radiation, magnetic stray field gradients in microfluidic systems, non-reciprocal microwave absorption, and super-capacitive devices for which a very large surface area and controlled morphology are key requirements. A novel electrochemical methodology for the growth of arrays of Ni and Co nanowires (NWs) with linear and non-linear varying micro-height gradient profiles (μHGPs), has been developed.![]()
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Affiliation(s)
- Juan Patiño Cárdenas
- Instituto de Investigaciones en Materiales – Unidad Morelia
- Universidad Nacional Autónoma de México
- Morelia
- Mexico
| | - Armando Encinas
- División de Materiales Avanzados
- Instituto Potosino de Investigación Científica y Tecnológica A. C
- 78216 San Luis Potosí, SLP
- Mexico
| | - Rossana Ramírez Villegas
- Instituto de Investigaciones en Materiales – Unidad Morelia
- Universidad Nacional Autónoma de México
- Morelia
- Mexico
| | - Joaquín de la Torre Medina
- Instituto de Investigaciones en Materiales – Unidad Morelia
- Universidad Nacional Autónoma de México
- Morelia
- Mexico
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