Stretchable Electromagnetic Interference Research Articles

Highly stretchable and strain-insensitive multilayered electromagnetic interference shielding films prepared via a simple soaking-infiltration strategy

Stretchable electromagnetic interference (EMI) shielding films are crucial for wearable electronics. However, it is challenging to further endow the EMI shielding films with good stretchability and satisfactory EMI shielding effectiveness (EMI SE) under large strains. Herein, we successfully prepared high-performance stretchable polydimethylsiloxane (PDMS)/ single-walled carbon nanotube buckypaper (SWNT BP)/PDMS EMI shielding films with multi-graded conductive networks via a soaking-infiltration strategy. In this multilayered film, infiltration layers of SWNT/PDMS were particularly created between elastic PDMS and brittle SWNT BP. Owing to the multilayered structure and conductivity compensation effects arising from infiltration layers, our EMI shielding films exhibited excellent EMI SE of 34.2 dB with high stretchability of >400%. The outstanding EMI SE could be well maintained under large strains. At <50% strain, the relative change in EMI SE (|ΔSE/SE0|) remained consistently below 10%, while at even 100% strain, |ΔSE/SE0| was only ∼35%. Furthermore, we proposed a parallel-series hybrid model to describe electrical conduction in straining films. Due to their excellent conductivity under strain, the films could also serve as stretchable Joule heaters. This work provides a novel and simple approach for constructing strain-insensitive conductive films, with potential applications in stretchable EMI shielding and thermal management.

Silver nanoparticles bridging liquid metal for wearable electromagnetic interference fabric

Stretchable conductive fibers are essential for the advancement of wearable electronic textiles. However, a significant challenge arises as their conductivity sharply decreases when stretched due to disruptions in electronic transport. Coating fibers with soft liquid metal (LM) has emerged as a promising solution. Despite this, there remains an urgent need to develop methods that enhance LM adhesion to substrates while facilitating efficient electron transport pathways. This study demonstrates a novel Ag-LM conductive network strategy for fabricating a thermoplastic polyurethane/polydopamine/silver-LM (TPU/PDA/Ag-LM) fiber membrane. This membrane exhibits outstanding stretchable electromagnetic interference (EMI) shielding performance and is produced through straightforward electrospinning, electroless depositing, and LM coating and activation. The TPU/PDA/Ag fiber membrane is initially prepared via polydopamine-assisted deposition of silver nanoparticles (AgNPs) on electrospun TPU fibers. The presence of AgNPs on the surface of TPU/PDA fibers enhances LM adhesion to the substrate and bridges adjacent LM to establish efficient conductive paths. This interaction benefits from the reactive alloying between AgNPs and LM, where the LM infiltrates the gaps among AgNPs, forming a distinctive LM-Ag alloy layer that uniformly coats the surface of TPU fibers. As anticipated, the unique three-dimensional (3D) interconnected LM-Ag conductive network remains intact during stretching, ensuring strain-invariant conductivity. The fabricated TPU/PDA/Ag-LM fiber membrane demonstrates exceptional EMI shielding effectiveness (SE) of 77.4 dB within the frequency range of 8.2–12.8 GHz and maintains an excellent EMI SE of 37.2 dB under extensive tensile deformation of 300%. Furthermore, the TPU/PDA/Ag-LM fiber membrane shows remarkable mechanical properties and stable Joule heating performance even under significant stretching.

A super-stretchable conductive film with strain-insensitive conductivity for stretchable EMI shielding materials and wearable capacitive strain sensors

Strain-insensitive conductive films as stretchable electromagnetic interference (EMI) shielding materials and stretchable electrodes are highly desired in wearable electronics. However, fabricating super strain-insensitive conductive films under a tensile strain higher than 400 % is still a great challenge. Herein, a super-stretchable conductive film based on the crumple-structured Ti3C2Tx nanosheets-single walled carbon nanotubes/stretchable substrate double-layers is designed for the stretchable EMI shielding materials and electrodes. The resulting film exhibits a strain-insensitive electrical conductivity as high as 3.01 × 103 S/m even at a strain up to 500 %, which endows the film with a high and stable electromagnetic interference shielding efficiency (EMI SE) value of ∼45 dB. More interestingly, the EMI SE value of the film remains nearly constant even after 2000 cycles of 500 % tensile strain, indicating the excellent long-term service stability as a stretchable EMI shielding material. Moreover, a capacitive strain sensor with extra-wide sensing range, ultra-high stability, and excellent durability is successfully achieved by employing the as-prepared films as stretchable electrodes. This work proposes a convenient strategy of strain-insensitive conductive film aiming to design stretchable EMI shielding materials and electrodes for wearable electronics.

Ultrathin-flexible multifunctional MXene composite hydrogels with good mechanical properties-high strain sensitivity and ultra-broadband EMI shielding performances

Conductive hydrogels show excellent application potential in flexible and stretchable electromagnetic interference (EMI) shielding materials due to their water-rich porous structure and tissue-like mechanical properties. However, integrating multiple functions into EMI shielding materials remains challenging, including ultra-broadband EMI shielding, mechanical properties, strain sensitivity, flexibility, etc., with high performance. Here, through a straightforward and scalable combination of ultrasound-assisted dispersion and thermal polymerization, we have successfully synthesized the MXene/PE-CS composite hydrogels composed of acrylic acid (AA), 2-(Dimethylamino) ethyl methacrylate (DMAEMA), and chitosan (CS). It exhibits more comprehensive and excellent functionalities including high stretchability (0.47 MPa, 747 %), strain sensitivity (11.2), ultralow thickness (0.5–2.0 mm), good adhesion (0.13 MPa), and flexibility. More importantly, it achieves excellent shielding performance of more than 99.99 % in ultra-broadband (X-band, Ka-band, Ku-band, and THz-band) under ultralow thickness (0.5–2 mm) and MXene (transition metal carbides/nitrides) content (0.46 wt%), and the shielding properties can be dynamically controlled through MXene content, PE content and hydrogel thickness. Even after repeated stretching, bending, and long-term water evaporation, it still exhibits stable and high-performance EMI shielding performance. Our MXene/PE-CS composite hydrogels exhibit potential applications in ultra-broadband shielding for new generation flexible wearable electronic devices.

Recyclable and leakage-suppressed microcellular liquid–metal composite foams for stretchable electromagnetic shielding

The metallic conductivity and high liquidity of liquid metal (LM) make LM-polymer composites exhibit high electrical conductivity, large stretchability, and excellent mechanical–electrical decoupling, which provide significant advantages in the fabrication of stretchable electromagnetic interference (EMI) shielding materials. However, problems such as undesired LM leakage, high density, and poor recyclability due to the frequent use of chemically cross-linked polymers limit the applications of LM-polymer composites. Herein, we report the fabrication of stretchable and recyclable microcellular thermoplastic polyurethane (TPU)/LM composite foams (TLFs) with controllable LM distribution through a water–vapor-induced phase separation (WVIPS) process. The sedimentation of LM droplets helps to improve the shielding effectiveness (SE) of TLF, while the microcellular structure enables TLF with more uniform LM dispersion to achieve high leakage resistance. Moreover, the stretch-activated TLF shows high electrical stability with only slight resistance changes during stretching and exhibits a strain-insensitive shielding behavior. As a stretchable joule heater, the sample has outstanding Joule-heating performance, with stable temperature dropping only slightly under large tensile strains. More importantly, the excellent solubility of TPU, combined with a solution-based WVIPS process, allows our TLFs to be easily recycled into new products with very similar structure and performance to those before recycling, indicating the ideal recyclability of such materials.

Ti3C2Tx MXene- and Sulfuric Acid-Treated Double-Network Hydrogel with Ultralow Conductive Filler Content for Stretchable Electromagnetic Interference Shielding.

Hydrogels are emerging as stretchable electromagnetic interference (EMI) shielding materials because of their tissue-like mechanical properties and water-rich porous cellular structures. However, achieving high-performance hydrogel shields remains a challenge because enhancing conductivity often results in a compromise in deformation adoptability. This work proposes a treatment strategy involving sulfuric acid/titanium carbide MXene, which can simultaneously enhance the conductivity and stretchability of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/poly(vinyl alcohol) (PVA) double-network hydrogels. Multiple spectroscopic characterizations reveal that sulfuric acid promotes the linear conformation transition of the PEDOT molecular chain, while MXene increases charge delocalization and hydrogen bond cross-linking sites. The hydrogels, synthesized with a combined content of 0.6 wt % of MXene and PEDOT:PSS, exhibit an average X-band EMI SE of 41 dB. This performance is sustained at 94.5%, even following stretching and release at a strain of 200%. Interestingly, the EMI SE is found to linearly increase, reaching a value of 99 dB as the frequency is increased to 26.5 GHz. This increase is attributed to the enhanced water molecular polarization process, as supported by theoretical calculations of the impedance and attenuation constant. This work introduces a post-treatment technique that optimizes double-network hydrogels, providing deep insights into their EMI shielding mechanism and enabling high-performance EMI shielding with an ultralow conductive filler content.

Liquid metal based conductive textile via reactive wetting for stretchable electromagnetic shielding and electro-thermal conversion applications

Developing stretchable electromagnetic interference (EMI) shielding fabrics has long been fascinating, but remains challenging. Inspired by the fluidity of GaInSn based liquid metal (LM), a series of conductive and stretchable textiles was successfully fabricated here. Notably, the collaboration between Ag nanoparticles and flexible LM coating give rise to metallic electrical conductivity (5637 S/m) and distinguished EMI shielding effectiveness (112.8 dB), together with a remarkable shielding value (96.2 dB) even under stretching. Such a well-established conductive pathway can further yield favorable Joule heating performance that enables low-voltage driving warmth retention. Moreover, the LM coating deliver anti-fouling property and robust fastness on the textile substrate, with no discernible reduction in EMI SE observed even after repetitive strain or cyclic washing. These fascinating features, together with the easy processability, are believed to further drive the structure design of novel conductive textile toward wearable applications.

Multifunctional strain-activated liquid-metal composite films with electromechanical decoupling for stretchable electromagnetic shielding.

The increasing miniaturization and intelligence of flexible electronic devices pose a challenge to the facile and scalable fabrication of multifunctional stretchable electromagnetic interference (EMI) shielding films with strain-stable shielding effectiveness (SE). This paper presents a highly stretchable liquid metal/thermoplastic polyurethane (LM/TPU) composite film produced via a facile method of scraping and pre-stretching induced activation. The TPU matrix endows the activated LM/TPU (ALMT) film with excellent tensile properties (elongation at break >700%), and the stable and malleable three-dimensional conductive LM network enables the ALMT film to exhibit almost negligible resistance changes and strain-enhanced conductivity during stretching, resulting in excellent strain-insensitive far-field and near-field shielding capabilities. Moreover, the high EMI SE up to ∼60 dB in the tensile state (0-400%) and reduced thickness from ∼75 to ∼50 μm during stretching allow the SE/thickness values of the ALMT film to increase from ∼700 to ∼1200 dB mm-1, outperforming most of the reported LM/polymer composites. Furthermore, the stretchability of the ALMT film provides efficient Joule-heating performance even under substantial deformation, and it can also serve as a strain sensor for real-time monitoring of human motion. The strain-insensitive EMI shielding behavior as well as the outstanding Joule heating and sensing performance of the ALMT film renders it a promising candidate for next-generation flexible electronic devices.

Transparent and Stretchable Electromagnetic Interference Shielding Film with Fence-like Aligned Silver Nanowire Conductive Network.

Flexible transparent conductive electrodes (TCEs) that can be used as electromagnetic interference (EMI) shielding materials have a great potential for use as electronic components in optical window and display applications. However, development of TCEs that display high shielding effectiveness (SE) and good stretchability for flexible electronic device applications has proven challenging. Herein, this study describes a stretchable polydimethylsiloxane (PDMS)/silver nanowire (AgNW) TCE with a fence-like aligned conductive network that is fabricated via pre-stretching method. The fence-like AgNW network endowed the PDMS/AgNW film with excellent optoelectronic properties, i.e., low sheet resistance of 7.68Ωsq-1 at 73.7% optical transmittance, thus causing an effective EMI SE of 32.2dB at X-band. More importantly, the fence-like aligned AgNW conductive network reveals a high stability toward tensile deformation, thus gives the PDMS/AgNW film stretch-stable conductivity and EMI shielding property in the strain range of 0-100%. Typically, the film can reserve ≈70% or 80% of its initial EMI SE when stretching at 100% strain or stretching/releasing (50% strain) for 128 cycles, respectively. Additionally, the film exhibits a low-voltage driven and stretchable Joule heating performance. With these overall performances, the PDMS/AgNW film should be well suited for use in flexible and stretchable optical electronic devices.

Stretchable polymer composite film based on pseudo-high carbon-filler loadings for electromagnetic interference shielding

Polymer composites with carbon-based filler (C-filler) are regarded as promising alternatives for flexible and stretchable electromagnetic interference (EMI) shielding materials. However, the poor mechanical properties caused by high-loadings largely hinders their practical applications, especially for the film. Herein, a class of pseudo-high C-filler (PHCF) composite films are constructed by introducing lean C-filler polymer phase on both sides of the high C-filler polymer phase. Not only does conductive structure of the high C-filler phase not transform, but the lean C-filler phase serves as both absorbing microwaves and supporting function. Strong interfacial compatibility and multi-level “zigzag” cracks synergistically enhance the mechanical stretchability with elongation at break of 200 ± 8%. Notably, its EMI shielding effectiveness reaches 31.8 dB with enhanced absorptivity (>0.2). Further, EMI shielding performance remains reliable after bending and stretching. This work offers a regulation strategy to upgrade EMI shielding materials for burgeoning stretchable, wearable and mini electronics.

Highly stretchable and conformal electromagnetic interference shielding armor with strain sensing ability

Lightweight and stretchable electromagnetic interference (EMI) shielding materials are desirable for wearable electronics. Herein, a graphene armor composed of laminated graphene film (LGF) and hierarchical porous graphene foam (HGF) with film/foam/film sandwich architecture is reported for human EMI shielding and motion monitoring. The LGF with micron-level interlayer spacing (∼2 μm) is fabricated by laser induction in a single step under an ambient atmosphere. Attributed to abundant interfaces and excellent electrical conductivity of 1670 S/m, the LGF exhibits an EMI shielding effectiveness (SE) up to 36.3 dB at a thickness of 19.4 μm. Due to the three-dimensional porous foam structure with the tunability of graphene content, the EMI SE of the HGF can range from 10 to 80 dB. Based on HGF with a graphene content of 27 wt%, the sandwich graphene armor with a thickness of about 2 mm exhibits an EMI SE up to 69.8 dB at an ultralow density of 0.228 g/cm3. Furthermore, the graphene armor possesses excellent mechanical properties as strain sensors that the gauge factor can reach 258 at the strain range up to 100%, thus the graphene armor can be used for motion monitoring while protecting the joints of the human body. The results demonstrate that sandwich architecture can not only enhance the EMI shielding performance of foam materials but also be an effective approach to improving the sensitivity of strain sensors. Therefore, the highly stretchable, conformal, and lightweight sandwich graphene armor is promising for multifunctional applications of EMI shielding and strain sensing.

Highly stretchable graphene/polydimethylsiloxane composite lattices with tailored structure for strain-tolerant EMI shielding performance

The fast-growing wearable and portable electronics bring imperative demand for high-performance stretchable electromagnetic interference (EMI) shielding materials to tackle the issue of electromagnetic (EM) wave pollution. In this work, highly stretchable and conductive graphene/polydimethylsiloxane lattices are fabricated through a facile 3D printing technique. Benefiting from the unique 3D interconnected and robust conductive network, the resultant composite lattices deliver excellent stretchability of 130%, tunable EMI shielding effectiveness (SE) as high as 45 dB, along with exceptional durability, showing over 90% retention of EMI SE even after 200 cycles of repeated stretching and releasing at strains up to 100%. In addition, the composite lattices exhibit outstanding shielding stability, because the deformation of lattice structure effectively shares the external strain, and the filaments perpendicular to the loading direction act as stabilizing layers preventing the steep resistance changes. The exceptional combination of mechanical properties and EMI shielding performance of the composite lattice provide a brand new perspective for next-generation flexible and stretchable electronics.

Stretchable electromagnetic interference shielding and antenna for wireless strain sensing by anisotropic micron-steel-wire based conductive elastomers* *Project supported by the State Key Development Program for Basic Research of China (Grant Nos. 2016YFA0200200 and 2017YFB0307001), the National Natural Science Foundation of China (Grant Nos. 51973093, U1533122, and 51773094), and the Natural Science Foundation of Tianjin, China (Grant No. 18JCZDJC36800).

We prepare stretchable elastic electromagnetic interference (EMI) shielding and stretchable antenna for wireless strain sensing using an elastic composite comprising commercial steel wool as a conducting element. The prepared elastic conductor shows anisotropic electrical properties in response to the external force. In the stretchable range, the electrical resistance abnormally decreases with the increase of tensile deformation. The EMI shielding effectiveness of the elastic conductor can reach above –30 dB under 80% tensile strain. The resonance frequency of the dipole antenna prepared by the elastic conductor is linearly correlated with the tensile strain, which can be used as a wireless strain sensor. The transmission efficiency is stable at about –15 dB when stretched to 50% strain, with attenuation less than 5%. The current research provides an effective solution for stretchable EMI shielding and wireless strain sensing integrated with signal transmission by an antenna.

Intrinsic elastic conductors with internal buckled electron pathway for flexible electromagnetic interference shielding and tumor ablation

The elastic conductor is crucial in wearable electronics and soft robotics. The ideal intrinsic elastic bulk conductors show uniform three-dimensional conductive networks and stable resistance during large stretch. A challenge is that the variation of resistance is high under deformation due to disconnection of conductive pathway for bulk elastic conductors. Our strategy is to introduce buckled structure into the conductive network, by self-assembly of a carbon nanotube layer on the interconnecting micropore surface of a prestrained foam, followed by strain relaxation. Both unfolding of buckles and flattening of micropores contributed to the stability of the resistance under deformation (2.0% resistance variation under 70% strain). Microstructural analysis and finite element analysis illustrated different patterns of two-dimensional buckling structures could be obtained due to the imperfections in the conductive layer. Applications as all-directional interconnects, stretchable electromagnetic interference shielding and electrothermal tumor ablation were demonstrated.

Highly Stretchable Electromagnetic Interference Shielding Materials Made with Conductive Microcoils Confined to a Honeycomb Structure.

With the rapid development of flexible electronic facilities, conventional electromagnetic interference (EMI) shielding materials cannot meet the increasing demands of flexible deformation and stable EMI shielding performance. To solve this problem, in this research, stretchable conductive microcoils made from Spirulina biotemplates were confined in an orderly manner in the microgrooves of a honeycomb mold and then were sintered to form stable and conductive honeycomb networks, followed by immersion in silicone rubber to fabricate deformable EMI shielding materials. The morphologies and structures of the samples were analyzed in detail, and the conductive performance, mechanical deformation capacity, and electromagnetic (EM) characteristics of the as-prepared materials under different deformation situations were studied. The results showed that the honeycomb-structured EMI shielding materials could maintain a stable electrical conductivity and EMI shielding property under repeated stretching from 0 to 50%. Notably, the EMI shielding effectiveness of samples with 0.4 mm thicknesses increase from 23.3-26.2 to 34.3-35.7 dB in the X-band (7.8-12.4 GHz) when the tested sample is stretched to 50%, which is higher than most values of stretchable EMI shielding materials ever reported. This electrical filler particle and body structure simultaneously deforming strategy will open new routes toward the development of deformable EMI shielding materials and broaden the EM range in applications such as flexible EM protection skins, wearable EM devices, and flexible displays.

Highly stretchable electromagnetic interference (EMI) shielding segregated polyurethane/carbon nanotube composites fabricated by microwave selective sintering

Microwave selective sintering is a green and efficient strategy to construct a segregated conductive network.

Stretchable Intrinsically Conductive Polymers for Wearable Thermotherapy and Electromagnetic Interface Shielding

Stretchable conductors can have important application in wearable electronics. We prepared stretchable conductors by blending poly(3,4-ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS, a conductive polymer) and elastomeric waterborne polyurethane (WPU) and demonstrated the application of the blends for thermotherapy and electromagnetic interference (EMI) shielding. Wearable heaters were fabricated by using the stretchable PEDOT:PSS/WPU blends. rGO was mixed into the to improve the temperature uniformity because rGO has high thermal conductivity while the polymers have very low thermal conductivity. The heater shows stable heating behavior under repetitive voltage on/off cycles, and the temperature remains almost unchanged under a tensile strain of up to 30%. The devices can be comfortably attached to the skin of humans, for example on the wrist, and they exhibit a uniform and stable heating profile even under mechanical disturbance. In addition, the PEDOT:PSS/WPU blends can be investigated for EMI shielding. Flexible or even stretchable electromagnetic interference (EMI) shielding materials with high performance are needed for wearable electronic systems. The PEDOT:PSS/WPU blends can exhibit a high EMI shielding effectiveness (SE) of about 62 dB over the X-band frequency range at a film thickness of only 0.15 mm.

Fabrication of a stretchable electromagnetic interference shielding silver nanoparticle/elastomeric polymer composite

Highly conductive and stretchable electromagnetic interference shielding (EMI) materials were developed using a silver nanoparticle/elastomeric polymer (NP/SBS) composite.