16.2 Flexible and stretchable thermoelectric devices
4 min read•august 9, 2024
Flexible and stretchable thermoelectric devices are revolutionizing . These innovative materials can bend, twist, and conform to various shapes, opening up exciting new applications in wearable tech and portable electronics.
By using organic polymers and carbon-based materials, these devices offer lightweight, low-cost alternatives to traditional rigid thermoelectrics. They're paving the way for self-powered gadgets that can harvest energy from body heat or the environment.
Polymer and Organic Thermoelectrics
Organic and Polymer-based Thermoelectric Materials
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Functional conductive nanomaterials via polymerisation in nano-channels: PEDOT in a MOF ... View original
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Reversible switching of PEDOT:PSS conductivity in the dielectric–conductive range through the ... View original
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Top images from around the web for Organic and Polymer-based Thermoelectric Materials
Functional conductive nanomaterials via polymerisation in nano-channels: PEDOT in a MOF ... View original
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Reversible switching of PEDOT:PSS conductivity in the dielectric–conductive range through the ... View original
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- Organic thermoelectrics utilize carbon-based compounds exhibiting semiconducting properties
- Polymer-based thermoelectrics employ long-chain molecules with repeating structural units
- conduct electricity through their conjugated backbone structure
- (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate) functions as a widely used conductive polymer in thermoelectric applications
- Organic and polymer-based materials offer advantages of flexibility, lightweight nature, and potential for low-cost production
- These materials typically have lower compared to inorganic counterparts, potentially leading to higher ZT values
Properties and Advantages of Organic Thermoelectrics
- allows for conforming to various shapes and surfaces
- Solution processability enables easy fabrication through printing or coating techniques
- Tunable electronic properties through chemical modifications or doping
- Abundance of carbon-based materials reduces dependency on rare or toxic elements
- Potential for large-area applications due to scalable production methods
- Lower operating temperatures compared to inorganic thermoelectric materials
- Biocompatibility of certain organic materials opens up possibilities for biomedical applications
Challenges and Future Directions
- Improving electrical conductivity while maintaining low thermal conductivity remains a key challenge
- Enhancing the of organic thermoelectric materials to increase power output
- Developing strategies to improve the long-term stability and durability of organic thermoelectric devices
- Exploring to combine the advantages of both material classes
- Investigating novel molecular designs and synthesis routes to optimize thermoelectric performance
- Addressing the trade-off between flexibility and thermoelectric efficiency in polymer-based systems
Carbon-based Thermoelectrics
Carbon Nanotubes in Thermoelectric Applications
- (CNTs) consist of rolled-up sheets of graphene with unique electronic properties
- (SWCNTs) and (MWCNTs) offer different characteristics for thermoelectric applications
- CNTs exhibit high electrical conductivity and low thermal conductivity along the tube axis
- at CNT junctions contributes to reduced thermal conductivity in CNT networks
- Doping and functionalization of CNTs can enhance their Seebeck coefficient and overall thermoelectric performance
- CNT-based thermoelectric materials can be fabricated into flexible films or composites
- Challenges include controlling the chirality and alignment of CNTs to optimize thermoelectric properties
Graphene-based Thermoelectric Materials
- Graphene consists of a single layer of sp2-bonded carbon atoms arranged in a hexagonal lattice
- High electrical conductivity and carrier mobility make graphene attractive for thermoelectric applications
- Graphene's thermal conductivity can be reduced through nanostructuring or introduction of defects
- (GO) and (rGO) offer tunable electronic properties for thermoelectric devices
- Graphene-based composites with polymers or inorganic materials can enhance overall thermoelectric performance
- Edge functionalization and doping of graphene sheets provide methods to modify electronic structure
- Challenges include scaling up production of high-quality graphene and controlling its properties consistently
Hybrid Carbon-based Thermoelectric Systems
- Combining different carbon allotropes (CNTs, graphene, fullerenes) creates synergistic effects
- Carbon-based thermoelectric materials can be integrated with organic polymers to form flexible composites
- Incorporation of metal nanoparticles or conductive fillers enhances charge transport in carbon-based systems
- Layered structures of carbon materials with varying properties can create effective thermoelectric devices
- Carbon-based thermoelectrics show potential for waste heat recovery in low-temperature applications
- Future research focuses on optimizing interfaces between different carbon materials and enhancing power factor
Applications of Flexible Thermoelectrics
Printed Thermoelectric Devices
- Printed thermoelectrics utilize additive manufacturing techniques to create flexible and customizable devices
- , inkjet printing, and 3D printing enable fabrication of thermoelectric materials on various substrates
- Thermoelectric inks formulated with organic materials, conductive polymers, or nanoparticles
- Printed devices allow for complex geometries and large-area coverage not easily achievable with traditional methods
- In-plane and out-of-plane printed thermoelectric generators offer different design possibilities
- Challenges include optimizing ink formulations, improving printing resolution, and ensuring uniform material properties
- Integration of printed thermoelectrics with other printed electronic components for self-powered systems
Wearable Thermoelectric Generators
- Wearable thermoelectric generators (TEGs) harvest body heat to power portable electronic devices
- Flexible and stretchable materials enable conforming to body contours for efficient heat collection
- Integration of TEGs into textiles or clothing creates "smart" fabrics with energy harvesting capabilities
- Wearable TEGs can power health monitoring devices, fitness trackers, or communication systems
- Design considerations include breathability, comfort, and durability in addition to thermoelectric performance
- Challenges involve managing heat flow in dynamic wearing conditions and optimizing power output
- Potential applications in military, healthcare, and consumer electronics sectors
- Future developments aim to improve power density and reduce the profile of wearable TEG systems
Key Terms to Review (26)
2D materials like graphene: 2D materials like graphene are substances that have a thickness of just one or two atomic layers, making them incredibly thin and lightweight while retaining unique electrical, thermal, and mechanical properties. Graphene, a single layer of carbon atoms arranged in a hexagonal lattice, is particularly notable for its exceptional conductivity and flexibility, which makes it ideal for use in advanced technologies such as flexible and stretchable thermoelectric devices.
Bismuth Telluride: Bismuth telluride (Bi2Te3) is a compound semiconductor known for its excellent thermoelectric properties, making it a popular material for thermoelectric devices. It has the unique ability to convert temperature differences into electric voltage and vice versa, which connects it to both power generation and cooling applications.
Carbon nanotubes: Carbon nanotubes are cylindrical nanostructures made of carbon atoms arranged in a hexagonal lattice, exhibiting remarkable mechanical, electrical, and thermal properties. These unique structures can be single-walled or multi-walled and are known for their exceptional strength-to-weight ratio and high electrical conductivity, making them ideal candidates for use in flexible and stretchable thermoelectric devices that require efficient heat management and enhanced performance.
Composite Structures: Composite structures refer to materials that are made from two or more constituent materials with significantly different physical or chemical properties. When combined, these materials create a structure that exhibits enhanced mechanical, thermal, or electrical properties, making them ideal for applications in flexible and stretchable thermoelectric devices. This combination allows for the integration of different functionalities, such as improved flexibility and better thermoelectric performance, essential for modern wearable technologies.
Conductive polymers: Conductive polymers are organic polymers that exhibit electrical conductivity due to the presence of conjugated structures within their molecular chains. These materials have unique properties that combine the mechanical flexibility of plastics with electrical conductivity, making them suitable for various applications, including flexible and stretchable devices.
Degradation under strain: Degradation under strain refers to the deterioration of material properties, such as electrical and thermal conductivity, when subjected to mechanical stress or deformation. This phenomenon is particularly significant in flexible and stretchable thermoelectric devices, as these materials need to maintain their performance while being bent, twisted, or stretched. Understanding how materials behave under strain is crucial for optimizing the design and functionality of these devices in practical applications.
Energy harvesting: Energy harvesting is the process of capturing and storing energy from external sources, such as ambient heat, light, or motion, to power devices or systems. This technique enables the conversion of waste or low-grade energy into usable electrical energy, enhancing the efficiency and sustainability of various applications. By integrating energy harvesting technologies, systems can reduce their reliance on conventional power sources, leading to innovations in device functionality and lifespan.
Four-probe method: The four-probe method is a technique used to measure the electrical conductivity of materials with high accuracy by minimizing contact resistance. This method involves using four separate probes placed in a linear arrangement to measure voltage and current, thus ensuring that the resistive effects of the probes themselves are reduced. This technique is particularly important in understanding charge carrier transport mechanisms, quantifying electrical properties accurately, and evaluating materials for flexible and stretchable thermoelectric devices.
Graphene oxide: Graphene oxide is a single-atom-thick material derived from graphite that contains oxygen functionalities, making it hydrophilic and enabling easy dispersion in water and other solvents. Its unique properties, including high surface area and electrical conductivity, make it an attractive candidate for use in flexible and stretchable thermoelectric devices, where the need for lightweight and adaptable materials is essential.
Hybrid organic-inorganic composites: Hybrid organic-inorganic composites are materials that combine organic and inorganic components at the molecular or nano level to achieve unique properties not found in either component alone. These composites leverage the advantages of both materials, such as the flexibility and lightweight nature of organic substances with the thermal and electrical stability of inorganic materials, making them particularly useful in applications like flexible and stretchable thermoelectric devices.
Interfacial bonding issues: Interfacial bonding issues refer to the challenges related to the adhesion between different materials in a composite structure, which can lead to reduced performance and reliability in flexible and stretchable thermoelectric devices. These issues arise due to differences in thermal expansion, mechanical properties, or chemical compatibility of the materials, affecting their ability to maintain a strong bond under various conditions. Understanding and addressing these issues is crucial for optimizing device efficiency and longevity.
Mechanical flexibility: Mechanical flexibility refers to the ability of a material or device to bend, stretch, or deform under external forces without breaking or losing functionality. This property is crucial for creating devices that can conform to various shapes and sizes, making them suitable for applications in wearable technology, portable electronics, and other innovative designs that require adaptability.
Multi-walled carbon nanotubes: Multi-walled carbon nanotubes (MWCNTs) are cylindrical nanostructures composed of multiple layers of graphene rolled up into a tube shape. They have unique electrical, thermal, and mechanical properties, making them highly desirable for use in flexible and stretchable thermoelectric devices. These properties allow MWCNTs to efficiently conduct heat and electricity while also maintaining flexibility, which is crucial for applications that require materials to bend or stretch without losing performance.
PEDOT:PSS: PEDOT:PSS is a conductive polymer blend consisting of poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(styrenesulfonic acid) (PSS). This material is well-known for its high conductivity, transparency, and excellent stability, making it a popular choice for applications in flexible and stretchable thermoelectric devices. Its unique properties allow it to serve as an effective hole transport layer and enhance the performance of thermoelectric materials by facilitating efficient charge transport.
Phonon Scattering: Phonon scattering refers to the process where phonons, the quantized modes of vibrations in a material, interact with various defects, impurities, or other phonons, leading to a change in their direction and energy. This phenomenon is crucial in determining the thermal conductivity of materials, impacting their efficiency in thermoelectric applications as it affects how heat is transported and managed within these systems.
Reduced Graphene Oxide: Reduced graphene oxide (rGO) is a form of graphene oxide that has undergone a reduction process to restore some of the electrical conductivity and structural integrity lost during oxidation. This material combines the unique properties of graphene, such as high electrical conductivity and mechanical strength, with the tunable properties imparted by its functional groups, making it suitable for various applications in flexible and stretchable thermoelectric devices.
Screen Printing: Screen printing is a technique used to transfer ink onto a substrate using a mesh screen, where areas not to be printed are blocked off. This method is particularly significant for creating flexible and stretchable thermoelectric devices, as it allows for precise patterns and designs that can conform to various shapes and materials. The versatility of screen printing makes it an ideal choice for producing components that require both functionality and adaptability in energy harvesting applications.
Seebeck Coefficient: The Seebeck coefficient is a measure of the thermoelectric voltage generated in response to a temperature difference across a material. It indicates how effectively a material can convert heat energy into electrical energy and is fundamental to understanding the performance of thermoelectric devices.
Silicon nanowires: Silicon nanowires are ultra-thin, one-dimensional structures made of silicon, typically with diameters in the nanometer range. They have unique electrical and thermal properties, which make them particularly interesting for applications in flexible and stretchable thermoelectric devices, enabling improved energy conversion efficiency and adaptability in various environments.
Single-walled carbon nanotubes: Single-walled carbon nanotubes (SWCNTs) are cylindrical structures made up of a single layer of carbon atoms arranged in a hexagonal lattice, forming a tube with diameters on the nanometer scale. These remarkable materials possess exceptional electrical, thermal, and mechanical properties, which make them particularly valuable in the development of flexible and stretchable thermoelectric devices.
Stretchability: Stretchability refers to the ability of a material to undergo significant deformation when subjected to tensile stress without breaking. This property is crucial for flexible and stretchable thermoelectric devices, as it allows these devices to maintain performance and integrity while being stretched or bent, which is essential for applications in wearable technology and flexible electronics.
Thermal conductivity: Thermal conductivity is a measure of a material's ability to conduct heat. It plays a crucial role in thermal transport processes, as it directly influences the efficiency of heat transfer in thermoelectric materials and devices, impacting their performance in energy conversion applications.
Thin-film thermoelectrics: Thin-film thermoelectrics refer to thermoelectric materials that are fabricated in thin layers, typically ranging from nanometers to a few micrometers in thickness. This method of fabrication allows for improved thermal and electrical properties, making them ideal for applications in energy conversion and cooling. Thin films also enable the development of devices that can be flexible or stretchable, further enhancing their potential applications.
Transfer Printing: Transfer printing is a technique used to create patterns or images on a substrate by transferring pre-printed designs from a carrier material. This method is particularly useful in the production of flexible and stretchable thermoelectric devices, as it allows for the integration of complex geometries and designs while maintaining the performance characteristics of the materials involved.
Wearable electronics: Wearable electronics are smart electronic devices that can be comfortably worn on the body, often integrating technology to monitor health, fitness, or provide connectivity. These devices are designed to be lightweight and flexible, enabling users to incorporate them into their daily lives seamlessly. The incorporation of advanced materials and devices, such as flexible and stretchable thermoelectric devices, enhances their functionality and comfort, allowing for continuous data collection without hindering movement.
Zt factor: The zt factor, or figure of merit, is a dimensionless quantity used to evaluate the efficiency of thermoelectric materials. It is defined as the ratio of the material's Seebeck coefficient squared to the product of its electrical resistivity and thermal conductivity. A higher zt factor indicates better thermoelectric performance, making it a critical parameter for assessing materials used in applications such as flexible and stretchable thermoelectric devices.