Two percolation thresholds and remarkably high dielectric permittivity in pristine carbon nanotube/elastomer composites

Shqau

J of Applied Polymer Sci

et al. 2020

A new material, classified as a soft mixed ionic–electronic conductor (MIEC), was fabricated through casting and curing of different ratios of single walled carbon nanotube (SWNTs), hyaluronic acid (HA), and acrylonitrile butadiene copolymer latex (NBR) and developed for noninvasive stimulation for electrotherapeutics. The morphology of the composite yielded high electrical conductivity and retention of elasticity. The interfacial charge transfer of the material showed that by increasing the HA loading the capacitive contribution decreased, while increasing SWNT loading decreased the interfacial resistance. The soft MIEC materials interfacial charge transfer was superior than current state‐of‐the art electrodes on the market. A layered configuration with high HA ratio at the skin interface and high SWNTs ratio at the stainless‐steel interface was created to induce the most optimal charge transfer. These soft MIEC electrodes will be extremely helpful in electrotherapeutic applications to eliminate the need for hydrogels, which can be unsuitable due the their lack long term durability and instability.

Section: Resultsmentioning

confidence: 79%

Soft mixed ionic–electronic conductive electrodes for noninvasive stimulation

Shqau

J of Applied Polymer Sci

et al. 2020

Macromol. Rapid Commun.

“…Therefore the addition of a filler close to the percolation threshold is desirable for maximum ε r enhancement, although this is also likely to increase the electric field . When incorporating carbon nanotubes, a percolation threshold as low as 0.07 wt% has been reported …”

Section: Extrinsic Approaches To Improve the Dielectric Properties Ofmentioning

confidence: 99%

Intrinsically Tuning the Electromechanical Properties of Elastomeric Dielectrics: A Chemistry Perspective

Ellingford

Bowen

McNally

et al. 2018

Dielectric elastomers have the capability to be used as transducers for actuation and energy harvesting applications due to their excellent combination of large strain capability (100-400%), rapid response (10 s), high energy density (10-150 kJ m ), low noise, and lightweight nature. However, the dielectric properties of non-polar elastomers such as dielectric permittivity ε , breakdown strength E , and dielectric loss ε ″, need to be enhanced for real world applications. The introduction of polar groups or structures into dielectric elastomers through covalently bonding is an attractive approach to 'intrinsically' induce a permanent polarity to the elastomers, and can eliminate the poor post-processing issues and breakdown strength of extrinsically modified materials, which have often been prepared by incorporation of fillers. This review discusses the chemical methods for modification of dielectric elastomers, such as hydrosilylation, thiol-ene click chemistry, azide click chemistry, and atom transfer radical polymerization. The effects of the type and concentration of polar groups on the dielectric and mechanical properties of the elastomers and their performance in actuation and harvesting systems are discussed. State-of-the-art developments and perspectives of modified dielectric elastomers for deformable energy generators and transducers are provided.

“…Titanium dioxide (TiO 2 ) [28] and barium titanate (BaTiO 3 ) [29] have reportedly served as high permittivity inorganic particles for improving the dielectric constants of elastomers. Conductive fillers enhance the dielectric constant of elastomers by increasing the effective electrode area or facilitating electronic polarization, such as carbon nanotubes (CNTs) [30,31], metal particles [26] and conductive polymers [32].…”

Section: Elastomers 234mentioning

confidence: 99%

Dielectric Elastomer Sensors

Ni¹,

Zhang²

2017

Elastomers

Dielectric elastomers (DEs) represent a class of electroactive polymers (EAPs) that exhibit a significant electromechanical effect, which has made them very attractive over the last several decades for use as soft actuators, sensors and generators. Based on the principle of a plane-parallel capacitor, dielectric elastomer sensors consist of a flexible and stretchable dielectric polymer sandwiched between two compliant electrodes. With the development of elastic polymers and stretchable conductors, flexible and sensitive dielectric elastomer tactile sensors, similar to human skin, have been used for measuring mechanical deformations, such as pressure, strain, shear and torsion. For high sensitivity and fast response, air gaps and microstructural dielectric layers are employed in pressure sensors or multiaxial force sensors. Multimodal dielectric elastomer sensors have been reported that can detect mechanical deformation but can also sense temperature, humidity, as well as chemical and biological stimulation in human-activity monitoring and personal healthcare. Hence, dielectric elastomer sensors have great potential for applications in soft robotics, wearable devices, medical diagnostic and structural health monitoring, because of their large deformation, low cost, ease of fabrication and ease of integration into monitored structures.