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Lu G, Ni E, Jiang Y, Wu W, Li H. Room-Temperature Liquid Metals for Flexible Electronic Devices. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2024; 20:e2304147. [PMID: 37875665 DOI: 10.1002/smll.202304147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 07/26/2023] [Indexed: 10/26/2023]
Abstract
Room-temperature gallium-based liquid metals (RT-GaLMs) have garnered significant interest recently owing to their extraordinary combination of fluidity, conductivity, stretchability, self-healing performance, and biocompatibility. They are ideal materials for the manufacture of flexible electronics. By changing the composition and oxidation of RT-GaLMs, physicochemical characteristics of the liquid metal can be adjusted, especially the regulation of rheological, wetting, and adhesion properties. This review highlights the advancements in the liquid metals used in flexible electronics. Meanwhile related characteristics of RT-GaLMs and underlying principles governing their processing and applications for flexible electronics are elucidated. Finally, the diverse applications of RT-GaLMs in self-healing circuits, flexible sensors, energy harvesting devices, and epidermal electronics, are explored. Additionally, the challenges hindering the progress of RT-GaLMs are discussed, while proposing future research directions and potential applications in this emerging field. By presenting a concise and critical analysis, this paper contributes to the advancement of RT-GaLMs as an advanced material applicable for the new generation of flexible electronics.
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Affiliation(s)
- Guixuan Lu
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), School of Materials Science and Engineering, Shandong University, Jinan, Shandong, 250061, China
| | - Erli Ni
- The Institute for Advanced Studies of Wuhan University, Wuhan University, Wuhan, Hubei, 430072, China
| | - Yanyan Jiang
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), School of Materials Science and Engineering, Shandong University, Jinan, Shandong, 250061, China
| | - Weikang Wu
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), School of Materials Science and Engineering, Shandong University, Jinan, Shandong, 250061, China
| | - Hui Li
- Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), School of Materials Science and Engineering, Shandong University, Jinan, Shandong, 250061, China
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Hamza A, Navale A, Song Q, Bhagwat S, Kotz-Helmer F, Pezeshkpour P, Rapp BE. 3D printed microfluidic valve on PCB for flow control applications using liquid metal. Biomed Microdevices 2024; 26:14. [PMID: 38289398 PMCID: PMC10827904 DOI: 10.1007/s10544-024-00697-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/04/2024] [Indexed: 02/01/2024]
Abstract
Direct 3D printing of active microfluidic elements on PCB substrates enables high-speed fabrication of stand-alone microdevices for a variety of health and energy applications. Microvalves are key components of microfluidic devices and liquid metal (LM) microvalves exhibit promising flow control in microsystems integrated with PCBs. In this paper, we demonstrate LM microvalves directly 3D printed on PCB using advanced digital light processing (DLP). Electrodes on PCB are coated by carbon ink to prevent alloying between gallium-based LM plug and copper electrodes. We used DLP 3D printers with in-house developed acrylic-based resins, Isobornyl Acrylate, and Diurethane Dimethacrylate (DUDMA) and functionalized PCB surface with acrylic-based resin for strong bonding. Valving seats are printed in a 3D caterpillar geometry with chamber diameter of 700 µm. We successfully printed channels and nozzles down to 90 µm. Aiming for microvalves for low-power applications, we applied square-wave voltage of 2 Vpp at a range of frequencies between 5 to 35 Hz. The results show precise control of the bistable valving mechanism based on electrochemical actuation of LMs.
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Affiliation(s)
- Ahmed Hamza
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110, Freiburg, Germany
| | - Anagha Navale
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110, Freiburg, Germany
| | - Qingchuan Song
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110, Freiburg, Germany
| | - Sagar Bhagwat
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110, Freiburg, Germany
| | - Frederik Kotz-Helmer
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110, Freiburg, Germany
| | - Pegah Pezeshkpour
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110, Freiburg, Germany.
| | - Bastian E Rapp
- Laboratory of Process Technology, NeptunLab, Department of Microsystem Engineering (IMTEK), University of Freiburg, 79110, Freiburg, Germany
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Bhagwat S, Hambitzer L, Prediger R, Zhu P, Hamza A, Kilian SK, Kluck S, Pezeshkpour P, Kotz-Helmer F, Rapp BE. Tungsten Oxide Coated Liquid Metal Electrodes via Galvanic Replacement as Heavy Metal Ion Sensors. SENSORS (BASEL, SWITZERLAND) 2024; 24:416. [PMID: 38257509 PMCID: PMC10819474 DOI: 10.3390/s24020416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 01/07/2024] [Accepted: 01/08/2024] [Indexed: 01/24/2024]
Abstract
Gallium liquid metals (LMs) like Galinstan and eutectic Gallium-Indium (EGaIn) have seen increasing applications in heavy metal ion (HMI) sensing, because of their ability to amalgamate with HMIs like lead, their high hydrogen potential, and their stable electrochemical window. Furthermore, coating LM droplets with nanopowders of tungsten oxide (WO) has shown enhancement in HMI sensing owing to intense electrical fields at the nanopowder-liquid-metal interface. However, most LM HMI sensors are droplet based, which show limitations in scalability and the homogeneity of the surface. A scalable approach that can be extended to LM electrodes is therefore highly desirable. In this work, we present, for the first time, WO-Galinstan HMI sensors fabricated via photolithography of a negative cavity, Galinstan brushing inside the cavity, lift-off, and galvanic replacement (GR) in a tungsten salt solution. Successful GR of Galinstan was verified using optical microscopy, SEM, EDX, XPS, and surface roughness measurements of the Galinstan electrodes. The fabricated WO-Galinstan electrodes demonstrated enhanced sensitivity in comparison with electrodes structured from pure Galinstan and detected lead at concentrations down to 0.1 mmol·L-1. This work paves the way for a new class of HMI sensors using GR of WO-Galinstan electrodes, with applications in microfluidics and MEMS for a toxic-free environment.
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Affiliation(s)
- Sagar Bhagwat
- Laboratory of Process Technology, NeptunLab, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg im Breisgau, Germany; (S.B.); (L.H.); (R.P.); (P.Z.); (A.H.); (S.K.); (P.P.); (B.E.R.)
| | - Leonhard Hambitzer
- Laboratory of Process Technology, NeptunLab, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg im Breisgau, Germany; (S.B.); (L.H.); (R.P.); (P.Z.); (A.H.); (S.K.); (P.P.); (B.E.R.)
| | - Richard Prediger
- Laboratory of Process Technology, NeptunLab, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg im Breisgau, Germany; (S.B.); (L.H.); (R.P.); (P.Z.); (A.H.); (S.K.); (P.P.); (B.E.R.)
| | - Pang Zhu
- Laboratory of Process Technology, NeptunLab, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg im Breisgau, Germany; (S.B.); (L.H.); (R.P.); (P.Z.); (A.H.); (S.K.); (P.P.); (B.E.R.)
| | - Ahmed Hamza
- Laboratory of Process Technology, NeptunLab, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg im Breisgau, Germany; (S.B.); (L.H.); (R.P.); (P.Z.); (A.H.); (S.K.); (P.P.); (B.E.R.)
| | - Sophia K. Kilian
- Hahn-Schickard, Georges-Köhler-Allee 103, 79110 Freiburg im Breisgau, Germany;
| | - Sebastian Kluck
- Laboratory of Process Technology, NeptunLab, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg im Breisgau, Germany; (S.B.); (L.H.); (R.P.); (P.Z.); (A.H.); (S.K.); (P.P.); (B.E.R.)
| | - Pegah Pezeshkpour
- Laboratory of Process Technology, NeptunLab, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg im Breisgau, Germany; (S.B.); (L.H.); (R.P.); (P.Z.); (A.H.); (S.K.); (P.P.); (B.E.R.)
| | - Frederik Kotz-Helmer
- Laboratory of Process Technology, NeptunLab, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg im Breisgau, Germany; (S.B.); (L.H.); (R.P.); (P.Z.); (A.H.); (S.K.); (P.P.); (B.E.R.)
- Freiburg Materials Research Center (FMF), University of Freiburg, Stefan-Meier-Straße 21, 79104 Freiburg im Breisgau, Germany
| | - Bastian E. Rapp
- Laboratory of Process Technology, NeptunLab, Department of Microsystems Engineering (IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg im Breisgau, Germany; (S.B.); (L.H.); (R.P.); (P.Z.); (A.H.); (S.K.); (P.P.); (B.E.R.)
- Freiburg Materials Research Center (FMF), University of Freiburg, Stefan-Meier-Straße 21, 79104 Freiburg im Breisgau, Germany
- FIT Freiburg Center of Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg im Breisgau, Germany
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Bhagwat S, Goralczyk A, Luitz M, Sharieff L, Kluck S, Hamza A, Nekoonam N, Kotz-Helmer F, Pezeshkpour P, Rapp BE. In Situ Actuators with Gallium Liquid Metal Alloys and Polypyrrole-Coated Electrodes. ACS APPLIED MATERIALS & INTERFACES 2023; 15:10109-10122. [PMID: 36754363 PMCID: PMC9952059 DOI: 10.1021/acsami.2c17906] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 01/09/2023] [Indexed: 06/18/2023]
Abstract
Gallium liquid metal alloys (GLMAs) such as Galinstan and gallium-indium eutectic (EGaIn) are interesting materials due to their high surface tensions, low viscosities, and electrical conductivities comparable to classical solid metals. They have been used for applications in microelectromechanical systems (MEMS) and, more recently, liquid metal microfluidics (LMMF) for setting up devices like actuators. However, their high tendency to alloy with the most common metals used for electrodes such as gold (Au), platinum (Pt), titanium (Ti), nickel (Ni), and tungsten-titanium (WTi) is a major problem limiting the scaleup and applicability, e.g., liquid metal actuators. Stable electrodes are key elements for many applications and thus, the lack of an electrode material compatible with GLMAs is detrimental for many potential application scenarios. In this work, we study the effect of actuating Galinstan on various solid metal electrodes and present an electrode protection methodology that, first, prevents alloying and, second, prevents electrode corrosion. We demonstrate reproducible actuation of GLMA segments in LMMF, showcasing the stability of the proposed protective coating. We investigated a range of electrode materials including Au, Pt, Ti, Ni, and WTi, all in aqueous environments, and present the resulting corrosion/alloying effects by studying the interface morphology. Our proposed protective coating is based on a simple method to electrodeposit electrically conductive polypyrrole (PPy) on the electrodes to provide a conductive alloying-barrier layer for applications involving direct contact between GLMAs and electrodes. We demonstrate the versatility of this approach by direct three-dimensional (3D) printing of a 500 μm microfluidic chip on a set of electrodes onto which PPy is electrodeposited in situ for actuation of Galinstan plugs. The developed protection protocol will provide a generic, widely applicable strategy to protect a wide range of electrodes from alloying and corrosion and thus form a key element in future applications of GLMAs.
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Affiliation(s)
- Sagar Bhagwat
- Laboratory
of Process Technology, NeptunLab, Department of Microsystems Engineering
(IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
| | - Andreas Goralczyk
- Laboratory
of Process Technology, NeptunLab, Department of Microsystems Engineering
(IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
| | - Manuel Luitz
- Laboratory
of Process Technology, NeptunLab, Department of Microsystems Engineering
(IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
| | - Lathif Sharieff
- Laboratory
of Process Technology, NeptunLab, Department of Microsystems Engineering
(IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
| | - Sebastian Kluck
- Laboratory
of Process Technology, NeptunLab, Department of Microsystems Engineering
(IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
| | - Ahmed Hamza
- Laboratory
of Process Technology, NeptunLab, Department of Microsystems Engineering
(IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
| | - Niloofar Nekoonam
- Laboratory
of Process Technology, NeptunLab, Department of Microsystems Engineering
(IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
| | - Frederik Kotz-Helmer
- Laboratory
of Process Technology, NeptunLab, Department of Microsystems Engineering
(IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
- Freiburg
Materials Research Center (FMF), University
of Freiburg, Stefan-Meier-Straße
21, 79104 Freiburg, Germany
| | - Pegah Pezeshkpour
- Laboratory
of Process Technology, NeptunLab, Department of Microsystems Engineering
(IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
- Freiburg
Materials Research Center (FMF), University
of Freiburg, Stefan-Meier-Straße
21, 79104 Freiburg, Germany
| | - Bastian E. Rapp
- Laboratory
of Process Technology, NeptunLab, Department of Microsystems Engineering
(IMTEK), University of Freiburg, Georges-Köhler-Allee 103, 79110 Freiburg, Germany
- Freiburg
Materials Research Center (FMF), University
of Freiburg, Stefan-Meier-Straße
21, 79104 Freiburg, Germany
- FIT
Freiburg Center of Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany
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Zhou L, Li Y, Xiao J, Chen SW, Tu Q, Yuan MS, Wang J. Liquid Metal-Doped Conductive Hydrogel for Construction of Multifunctional Sensors. Anal Chem 2023; 95:3811-3820. [PMID: 36747339 DOI: 10.1021/acs.analchem.2c05118] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Interest in wearable and stretchable multifunctional sensors has grown rapidly in recent years. The sensing elements must accurately detect external stimuli to expand their applicability as sensors. However, the sensor's self-healing and adhesion to a target object have been major challenges in developing such practical and versatile devices. In this study, we prepared a hydrogel (LM-SA-PAA) composed of liquid metal (LM), sodium alginate (SA), and poly(acrylic acid) (PAA) with ultrastretchable, excellent self-healing, self-adhesive, and high-sensitivity sensing capabilities that enable the conformal contact between the sensor and skin even during dynamic movements. The excellent self-healing performance of the hydrogel stems from its double cross-linked networks, including physical and chemical cross-linked networks. The physical cross-link formed by the ionic interaction between the carboxyl groups of PAA and gallium ions provide the hydrogel with reversible autonomous repair properties, whereas the covalent bond provides the hydrogel with a stable and strong chemical network. Alginate forms a microgel shell around LM nanoparticles via the coordination of its carboxyl groups with Ga ions. In addition to offering exceptional colloidal stability, the alginate shell has sufficient polar groups, ensuring that the hydrogel adheres to diverse substrates. Based on the efficient electrical pathway provided by the LM, the hydrogel exhibited strain sensitivity and enabled the detection of various human motions and electrocardiographic monitoring. The preparation method is simple and versatile and can be used for the low-cost fabrication of multifunctional sensors, which have broad application prospects in human-machine interface compatibility and medical monitoring.
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Affiliation(s)
- Lingtong Zhou
- College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shaanxi 712100, P. R. China
| | - Yuanchang Li
- College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shaanxi 712100, P. R. China
| | - Jingcheng Xiao
- College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shaanxi 712100, P. R. China
| | - Shu-Wei Chen
- College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shaanxi 712100, P. R. China
| | - Qin Tu
- College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shaanxi 712100, P. R. China
| | - Mao-Sen Yuan
- College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shaanxi 712100, P. R. China
| | - Jinyi Wang
- College of Chemistry & Pharmacy, Northwest A&F University, Yangling, Shaanxi 712100, P. R. China
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