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Del Bosque A, Sánchez-Romate XF, Sánchez M, Ureña A. Toward flexible piezoresistive strain sensors based on polymer nanocomposites: a review on fundamentals, performance, and applications. NANOTECHNOLOGY 2024; 35:292003. [PMID: 38621367 DOI: 10.1088/1361-6528/ad3e87] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 04/15/2024] [Indexed: 04/17/2024]
Abstract
The fundamentals, performance, and applications of piezoresistive strain sensors based on polymer nanocomposites are summarized herein. The addition of conductive nanoparticles to a flexible polymer matrix has emerged as a possible alternative to conventional strain gauges, which have limitations in detecting small strain levels and adapting to different surfaces. The evaluation of the properties or performance parameters of strain sensors such as the elongation at break, sensitivity, linearity, hysteresis, transient response, stability, and durability are explained in this review. Moreover, these nanocomposites can be exposed to different environmental conditions throughout their lifetime, including different temperature, humidity or acidity/alkalinity levels, that can affect performance parameters. The development of flexible piezoresistive sensors based on nanocomposites has emerged in recent years for applications related to the biomedical field, smart robotics, and structural health monitoring. However, there are still challenges to overcome in designing high-performance flexible sensors for practical implementation. Overall, this paper provides a comprehensive overview of the current state of research on flexible piezoresistive strain sensors based on polymer nanocomposites, which can be a viable option to address some of the major technological challenges that the future holds.
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Affiliation(s)
- Antonio Del Bosque
- Technology, Instruction and Design in Engineering and Education Research Group (TiDEE.rg), Catholic University of Ávila, C/Canteros s/n, E-05005 Ávila, Spain
| | - Xoan F Sánchez-Romate
- Materials Science and Engineering Area, Higher School of Experimental Sciences and Technology, Rey Juan Carlos University, C/Tulipán s/n, Móstoles, E-28933 Madrid, Spain
| | - María Sánchez
- Materials Science and Engineering Area, Higher School of Experimental Sciences and Technology, Rey Juan Carlos University, C/Tulipán s/n, Móstoles, E-28933 Madrid, Spain
- Instituto de Tecnologías Para la Sostenibilidad, Rey Juan Carlos University, C/Tulipán s/n, E-28933 Móstoles, Madrid, Spain
| | - Alejandro Ureña
- Materials Science and Engineering Area, Higher School of Experimental Sciences and Technology, Rey Juan Carlos University, C/Tulipán s/n, Móstoles, E-28933 Madrid, Spain
- Instituto de Tecnologías Para la Sostenibilidad, Rey Juan Carlos University, C/Tulipán s/n, E-28933 Móstoles, Madrid, Spain
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Georgopoulou A, Diethelm P, Wagner M, Spolenak R, Clemens F. Soft Self-Regulating Heating Elements for Thermoplastic Elastomer-Based Electronic Skin Applications. 3D PRINTING AND ADDITIVE MANUFACTURING 2024; 11:e828-e838. [PMID: 38689932 PMCID: PMC11057689 DOI: 10.1089/3dp.2022.0242] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2024]
Abstract
Resistive heating elements can be of particular interest for many applications, such as e-skin. In this study, soft heating elements were developed by combining thermoplastic polyurethane (TPU) with carbon black. In contrast to previous studies on thermoplastic polymer-based thermistors, the heating elements could endure elongations above 100%. Due to the high melting point of the TPU and the carbon filler, the thermistors could be heated up to 180°C without significant deformation. The heating elements were extruded on TPU substrates using material extrusion additive manufacturing in one-step process. Self-regulating behavior to control the maximum temperature was achieved with the application of two different voltages (20 and 25 V) and different current thresholds, between 100 and 800 mA. The heating performance was adjusted by changing the geometry of the sensing elements; an increase in cross section resulted in a lower current density and lower temperature. For the heating elements, variation of the additive manufacturing parameters such as offset, layer height, nozzle speed, and extrusion multiplier resulted in a different width/height aspect ratio of the cross section of the extruded lines, affecting the initial resistivity of the thermistor. Orientation of the carbon filler during extrusion process is one reason for the small change of the longitudinal conductivity of the heating elements. The resulting skin with the integrated heating elements allowed the possibility to perform the in situ heating for the localized healing of structural damage, while maintaining the softness required for the application of soft robotic electronic skin.
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Affiliation(s)
- Antonia Georgopoulou
- Department of Functional Materials, Empa–Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
- Brubotics, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Pascal Diethelm
- Department of Functional Materials, Empa–Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
| | - Marius Wagner
- Laboratory for Nanometallurgy, Department of Materials, ETH Zürich, Zürich, Switzerland
| | - Ralph Spolenak
- Laboratory for Nanometallurgy, Department of Materials, ETH Zürich, Zürich, Switzerland
| | - Frank Clemens
- Department of Functional Materials, Empa–Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
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Mousavi A, Rahimnejad M, Azimzadeh M, Akbari M, Savoji H. Recent advances in smart wearable sensors as electronic skin. J Mater Chem B 2023; 11:10332-10354. [PMID: 37909384 DOI: 10.1039/d3tb01373a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2023]
Abstract
Flexible and multifunctional electronic devices and soft robots inspired by human organs, such as skin, have many applications. However, the emergence of electronic skins (e-skins) or textiles in biomedical engineering has made a great revolution in a myriad of people's lives who suffer from different types of diseases and problems in which their skin and muscles lose their appropriate functions. In this review, recent advances in the sensory function of the e-skins are described. Furthermore, we have categorized them from the sensory function perspective and highlighted their advantages and limitations. The categories are tactile sensors (including capacitive, piezoresistive, piezoelectric, triboelectric, and optical), temperature, and multi-sensors. In addition, we summarized the most recent advancements in sensors and their particular features. The role of material selection and structure in sensory function and other features of the e-skins are also discussed. Finally, current challenges and future prospects of these systems towards advanced biomedical applications are elaborated.
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Affiliation(s)
- Ali Mousavi
- Institute of Biomedical Engineering, Department of Pharmacology and Physiology, Faculty of Medicine, University of Montreal, Montreal, QC, H3T 1J4, Canada.
- Research Center, Sainte-Justine University Hospital, Montreal, QC, H3T 1C5, Canada
- Montreal TransMedTech Institute, Montreal, QC, H3T 1J4, Canada
| | - Maedeh Rahimnejad
- Department of Cariology, Restorative Sciences, and Endodontics, School of Dentistry, University of Michigan, Ann Arbor, Michigan, USA
| | - Mostafa Azimzadeh
- Laboratory for Innovations in Micro Engineering (LiME), Department of Mechanical Engineering, University of Victoria, Victoria, BC, V8P 5C2, Canada
| | - Mohsen Akbari
- Laboratory for Innovations in Micro Engineering (LiME), Department of Mechanical Engineering, University of Victoria, Victoria, BC, V8P 5C2, Canada
| | - Houman Savoji
- Institute of Biomedical Engineering, Department of Pharmacology and Physiology, Faculty of Medicine, University of Montreal, Montreal, QC, H3T 1J4, Canada.
- Research Center, Sainte-Justine University Hospital, Montreal, QC, H3T 1C5, Canada
- Montreal TransMedTech Institute, Montreal, QC, H3T 1J4, Canada
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Sanchaniya JV, Lasenko I, Kanukuntla SP, Mannodi A, Viluma-Gudmona A, Gobins V. Preparation and Characterization of Non-Crimping Laminated Textile Composites Reinforced with Electrospun Nanofibers. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:1949. [PMID: 37446465 DOI: 10.3390/nano13131949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Revised: 06/24/2023] [Accepted: 06/26/2023] [Indexed: 07/15/2023]
Abstract
This research investigated the use of electrospun nanofibers as reinforcing laminates in textiles to enhance their mechanical properties for use as smart and technical textile applications. Crimping plays a crucial role in textiles. Because of crimp, fabrics have extensibility, compressibility, and improved quality. Although crimping is inevitable for fabrics used in smart textiles, it is also a disadvantage as it could weaken the fibers and reduce their strength and efficiency. The study focused on preparing laminated textile composites by electrospinning a polyacrylonitrile (PAN) polymer onto textile fabric. The research examined the effect of electrospun nanofibers on the fabric by using a tensile testing machine and scanning electron microscopy. The results revealed that the prepared laminated textile was crimp-free because of the orientation of the nanofibers directly electrospun on the fabric, which exhibited perfect bonding between the laminates. Additionally, the nanofiber-reinforced composite fabrics demonstrated a 75.5% increase in the elastic moduli and a 20% increase in elongation at breaking. The study concluded that the use of electrospun nanofibers as laminates in textile composites could enhance the elastic properties, and prepared laminated composites will have the advantages of nanofibers, such as crimp-free elastic regions. Furthermore, the mechanical properties of the laminated textile composite were compared with those of the micromechanical models, providing a deeper understanding of the behavior of these laminated composites.
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Affiliation(s)
- Jaymin Vrajlal Sanchaniya
- Mechanics and Biotextile Research Laboratory, Riga Technical University, 3/3-20 Pulka Street, LV-1007 Riga, Latvia
- Department of Theoretical Mechanics and Strength of Materials, Institute of Mechanics and Mechanical Engineering, Riga Technical University, 6B Kipsala Street, LV-1048 Riga, Latvia
| | - Inga Lasenko
- Mechanics and Biotextile Research Laboratory, Riga Technical University, 3/3-20 Pulka Street, LV-1007 Riga, Latvia
| | - Sai Pavan Kanukuntla
- Mechanics and Biotextile Research Laboratory, Riga Technical University, 3/3-20 Pulka Street, LV-1007 Riga, Latvia
- Department of Theoretical Mechanics and Strength of Materials, Institute of Mechanics and Mechanical Engineering, Riga Technical University, 6B Kipsala Street, LV-1048 Riga, Latvia
| | - Anunand Mannodi
- Department of Theoretical Mechanics and Strength of Materials, Institute of Mechanics and Mechanical Engineering, Riga Technical University, 6B Kipsala Street, LV-1048 Riga, Latvia
| | - Arta Viluma-Gudmona
- Mechanics and Biotextile Research Laboratory, Riga Technical University, 3/3-20 Pulka Street, LV-1007 Riga, Latvia
| | - Valters Gobins
- Laboratory of Environmental Genetics, Institute of Biology, Faculty of Biology, Latvian University, Jelgavas Street 1, LV-1004 Riga, Latvia
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Georgopoulou A, Srisawadi S, Wiroonpochit P, Clemens F. Soft Wearable Piezoresistive Sensors Based on Natural Rubber Fabricated with a Customized Vat-Based Additive Manufacturing Process. Polymers (Basel) 2023; 15:polym15102410. [PMID: 37242985 DOI: 10.3390/polym15102410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 05/09/2023] [Accepted: 05/14/2023] [Indexed: 05/28/2023] Open
Abstract
Piezoresistive sensors for monitoring human motions are essential for the prevention and treatment of injury. Natural rubber is a material of renewable origin that can be used for the development of soft wearable sensors. In this study, natural rubber was combined with acetylene black to develop a soft piezoresistive sensing composite for monitoring the motion of human joints. An additive manufacturing technique based on stereolithography was used, and it was seen that the sensors produced with the method could detect even small strains (<10%) successfully. With the same sensor composite fabricated by mold casting, it was not possible to detect low strains reliably. TEM microscopy revealed that the distribution of the filler was not homogeneous for the cast samples, suggesting a directionality of the conductive filler network. For the sensors fabricated through the stereolithography-based method, a homogeneous distribution could be achieved. Based on mechano-electrical characterization, it was seen that the samples produced with AM combined the ability to endure large elongations with a monotonic sensor response. Under dynamic conditions, the sensor response of the samples produced by 3D printing showed lower drift and lower signal relaxation. The piezoresistive sensors were examined for monitoring the motion of the human finger joints. By increasing the bending angle of the sensor, it was possible to increase the sensitivity of the response. With the renewable origin of natural rubber and manufacturing method, the featured sensors can expand the applicability of soft flexible electronics in biomedical applications and devices.
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Affiliation(s)
- Antonia Georgopoulou
- Department of Advanced Materials and Surfaces, Empa-Swiss Federal Laboratories for Material Science and Technology, Ueberlandstrasse 129, 8600 Dübendorf, Switzerland
| | - Sasitorn Srisawadi
- National Metal and Materials Technology Center, National Science and Technology Development Agency, 114 Thailand Science Park, Phahonyothin Road, Khlong Nueng, Khlong Luang, Pathum Thani 12120, Thailand
| | - Panithi Wiroonpochit
- National Metal and Materials Technology Center, National Science and Technology Development Agency, 114 Thailand Science Park, Phahonyothin Road, Khlong Nueng, Khlong Luang, Pathum Thani 12120, Thailand
| | - Frank Clemens
- Department of Advanced Materials and Surfaces, Empa-Swiss Federal Laboratories for Material Science and Technology, Ueberlandstrasse 129, 8600 Dübendorf, Switzerland
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Roels E, Terryn S, Iida F, Bosman AW, Norvez S, Clemens F, Van Assche G, Vanderborght B, Brancart J. Processing of Self-Healing Polymers for Soft Robotics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2104798. [PMID: 34610181 DOI: 10.1002/adma.202104798] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 09/27/2021] [Indexed: 06/13/2023]
Abstract
Soft robots are, due to their softness, inherently safe and adapt well to unstructured environments. However, they are prone to various damage types. Self-healing polymers address this vulnerability. Self-healing soft robots can recover completely from macroscopic damage, extending their lifetime. For developing healable soft robots, various formative and additive manufacturing methods have been exploited to shape self-healing polymers into complex structures. Additionally, several novel manufacturing techniques, noted as (re)assembly binding techniques that are specific to self-healing polymers, have been created. Herein, the wide variety of processing techniques of self-healing polymers for robotics available in the literature is reviewed, and limitations and opportunities discussed thoroughly. Based on defined requirements for soft robots, these techniques are critically compared and validated. A strong focus is drawn to the reversible covalent and (physico)chemical cross-links present in the self-healing polymers that do not only endow healability to the resulting soft robotic components, but are also beneficial in many manufacturing techniques. They solve current obstacles in soft robots, including the formation of robust multi-material parts, recyclability, and stress relaxation. This review bridges two promising research fields, and guides the reader toward selecting a suitable processing method based on a self-healing polymer and the intended soft robotics application.
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Affiliation(s)
- Ellen Roels
- Brubotics, Vrije Universiteit Brussel (VUB) and Imec, Pleinlaan 2, Brussels, 1050, Belgium
- Physical Chemistry and Polymer Science (FYSC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, Brussels, 1050, Belgium
| | - Seppe Terryn
- Brubotics, Vrije Universiteit Brussel (VUB) and Imec, Pleinlaan 2, Brussels, 1050, Belgium
- Physical Chemistry and Polymer Science (FYSC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, Brussels, 1050, Belgium
| | - Fumiya Iida
- Machine Intelligence Lab, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, UK
| | - Anton W Bosman
- SupraPolix B. V., Horsten 1.29, Eindhoven, 5612 AX, The Netherlands
| | - Sophie Norvez
- Chimie Moléculaire, Macromoléculaire, Matériaux, École Supérieure de Physique et de Chimie (ESPCI), 10 Rue Vauquelin, Paris, 75005, France
| | - Frank Clemens
- Laboratory for High Performance Ceramics, Swiss Federal Laboratories for Materials Science and Technology (EMPA), Überlandstrasse 129, Dübendorf, 8600, Switzerland
| | - Guy Van Assche
- Physical Chemistry and Polymer Science (FYSC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, Brussels, 1050, Belgium
| | - Bram Vanderborght
- Brubotics, Vrije Universiteit Brussel (VUB) and Imec, Pleinlaan 2, Brussels, 1050, Belgium
| | - Joost Brancart
- Physical Chemistry and Polymer Science (FYSC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, Brussels, 1050, Belgium
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Georgopoulou A, Vanderborght B, Clemens F. Fabrication of a Soft Robotic Gripper With Integrated Strain Sensing Elements Using Multi-Material Additive Manufacturing. Front Robot AI 2021; 8:615991. [PMID: 35372524 PMCID: PMC8965514 DOI: 10.3389/frobt.2021.615991] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Accepted: 09/24/2021] [Indexed: 01/01/2023] Open
Abstract
With the purpose of making soft robotic structures with embedded sensors, additive manufacturing techniques like fused deposition modeling (FDM) are popular. Thermoplastic polyurethane (TPU) filaments, with and without conductive fillers, are now commercially available. However, conventional FDM still has some limitations because of the marginal compatibility with soft materials. Material selection criteria for the available material options for FDM have not been established. In this study, an open-source soft robotic gripper design has been used to evaluate the FDM printing of TPU structures with integrated strain sensing elements in order to provide some guidelines for the material selection when an elastomer and a soft piezoresistive sensor are combined. Such soft grippers, with integrated strain sensing elements, were successfully printed using a multi-material FDM 3D printer. Characterization of the integrated piezoresistive sensor function, using dynamic tensile testing, revealed that the sensors exhibited good linearity up to 30% strain, which was sufficient for the deformation range of the selected gripper structure. Grippers produced using four different TPU materials were used to investigate the effect of the Shore hardness of the TPU on the piezoresistive sensor properties. The results indicated that the in situ printed strain sensing elements on the soft gripper were able to detect the deformation of the structure when the tentacles of the gripper were open or closed. The sensor signal could differentiate between the picking of small or big objects and when an obstacle prevented the tentacles from opening. Interestingly, the sensors embedded in the tentacles exhibited good reproducibility and linearity, and the sensitivity of the sensor response changed with the Shore hardness of the gripper. Correlation between TPU Shore hardness, used for the gripper body and sensitivity of the integrated in situ strain sensing elements, showed that material selection affects the sensor signal significantly.
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Affiliation(s)
- Antonia Georgopoulou
- Department of Functional Materials, Empa–Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
- Department of Mechanical Engineering (MECH), Vrije Universiteit Brussel (VUB), and Flanders Make, Brussels, Belgium
- *Correspondence: Antonia Georgopoulou, ; Frank Clemens,
| | - Bram Vanderborght
- Department of Mechanical Engineering (MECH), Vrije Universiteit Brussel (VUB), and Flanders Make, Brussels, Belgium
| | - Frank Clemens
- Department of Functional Materials, Empa–Swiss Federal Laboratories for Materials Science and Technology, Dübendorf, Switzerland
- *Correspondence: Antonia Georgopoulou, ; Frank Clemens,
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Supramolecular Self-Healing Sensor Fiber Composites for Damage Detection in Piezoresistive Electronic Skin for Soft Robots. Polymers (Basel) 2021; 13:polym13172983. [PMID: 34503023 PMCID: PMC8433753 DOI: 10.3390/polym13172983] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 08/26/2021] [Accepted: 08/28/2021] [Indexed: 11/16/2022] Open
Abstract
Self-healing materials can prolong the lifetime of structures and products by enabling the repairing of damage. However, detecting the damage and the progress of the healing process remains an important issue. In this study, self-healing, piezoresistive strain sensor fibers (ShSFs) are used for detecting strain deformation and damage in a self-healing elastomeric matrix. The ShSFs were embedded in the self-healing matrix for the development of self-healing sensor fiber composites (ShSFC) with elongation at break values of up to 100%. A quadruple hydrogen-bonded supramolecular elastomer was used as a matrix material. The ShSFCs exhibited a reproducible and monotonic response. The ShSFCs were investigated for use as sensorized electronic skin on 3D-printed soft robotic modules, such as bending actuators. Depending on the bending actuator module, the electronic skin was loaded under either compression (pneumatic-based module) or tension (tendon-based module). In both configurations, the ShSFs could be successfully used as deformation sensors, and in addition, detect the presence of damage based on the sensor signal drift. The sensor under tension showed better recovery of the signal after healing, and smaller signal relaxation. Even with the complete severing of the fiber, the piezoresistive properties returned after the healing, but in that case, thermal heat treatment was required. With their resilient response and self-healing properties, the supramolecular fiber composites can be used for the next generation of soft robotic modules.
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