Printable Dielectric Elastomers of High Electromechanical Properties Based on SEBS Ink Incorporated With Polyphenols Modified Dielectric Particles

In this work, a recently developed 3D additive processing technology termed electrohydrodynamic (EHD) printing was employed to fabricate dielectric elastomer (DE) films by using styrene-ethylene-butylene-styrene (SEBS) inks with the addition of high dielectric titanium dioxide (TiO2) nanoparticles. In order to improve the dispersibility of TiO2 in the SEBS matrix, extracted walnut polyphenols were utilized for surface modification of TiO2 nanoparticles labelled wp-TiO2. The effect of the applied voltage on the ink jet morphology of the obtained SEBS based inks during EHD printing was analyzed. The prepared films had precision patterned shapes and their morphology was studied. It revealed that the dispersibility of TiO2 nanoparticles in the SEBS matrix and their compatibility were greatly improved using this procedure. Furthermore, the printed DE films were found to have excellent mechanical, dielectric and electromechanical properties. For the range of DEs fabricated, the SEBS/10%wp-TiO2 composite exhibited the maximum actuated area strain of 21.5% at an electric field of about 34.0 V/μm without degradation of other properties

A flexible dual-mode pressure sensor with ultra-high sensitivity based on BTO@MWCNTs core-shell nanofibers

Wearable flexible sensors have developed rapidly in recent years because of their improved capacity to detect human motion in wide-ranging situations. In order to meet the requirements of flexibility and low detection limits, a new pressure sensor was fabricated based on electrospun barium titanate/multi-wall carbon nanotubes (BTO@MWCNTs) core-shell nanofibers coated with styrene-ethylene-butene-styrene block copolymer (SEBS). The sensor material (BTO@MWCNTs/SEBS) had a SEBS to BTO/MWCNTs mass ratio of 20:1 and exhibited an excellent piezoelectricity over a wide range of workable pressures from 1 to 50 kPa, higher output current of 56.37 nA and a superior piezoresistivity over a broad working range of 20 to 110 kPa in compression. The sensor also exhibited good durability and repeatability under different pressures and under long-term cyclic loading. These properties make the composite ideal for applications requiring monitoring subtle pressure changes (exhalation, pulse rate) and finger movements. The pressure sensor developed based on BTO@MWCNTs core-shell nanofibers has demonstrated great potential to be assembled into intelligent wearable devices

The 3D Printing of Dielectric Elastomer Films Assisted by Electrostatic Force

ompared with traditional methods for preparing dielectric elastomer (DE) films, electrohydrodynamic (EHD) 3D printing displays many advantages, notably full automation, computer control and flexible design. It also confers high printing resolution, high preparation efficiency with minimal probability of nozzle clogging. In this article, EHD 3D printing was employed to fabricate silicone rubber (SR) based DE films. In order to increase their dielectric constant, high dielectric copper phthalocyanine (CuPc) particles were added into the SR ink. Optimal printing conditions were determined by analyzing the effects of printing voltage and ink properties on the formation of liquid cone and the printed line width. The SR/CuPc composite film with 3 wt% CuPc particles (SR/CuPc-3) exhibits a high dielectric constant of 5.52, with a large actuated area strain of 23.7% under an electric field of 39.4 V μm−1. Furthermore, under 100 cycles of electric field loading, SR/CuPc-3 demonstrate excellent electromechanical stability, indicating that EHD 3D printing holds a considerable potential for fabricating high-performance DE films in an efficacious manner

A Highly Sensitive and Flexible Strain Sensor Based on Dopamine-Modified Electrospun Styrene-Ethylene-Butylene-Styrene Block Copolymer Yarns and Multi Walled Carbon Nanotubes

As wearable electronic devices have become commonplace in daily life, great advances in wearable strain sensors occurred in various fields including healthcare, robotics, virtual reality and other sectors. In this work, a highly stretchable and sensitive strain sensor based on electrospun styrene-ethylene-butene-styrene copolymer (SEBS) yarn modified by dopamine (DA) and coated with multi-walled carbon nanotubes (MWCNTs) was reported. Due to the process of twisting, a strain senor stretched to a strain of 1095.8% while exhibiting a tensile strength was 20.03 MPa. The strain sensor obtained a gauge factor (GF of 1.13 × 105) at a maximum strain of 215%. Concurrently, it also possessed good stability, repeatability and durability under different strain ranges, stretching speeds and 15,000 stretching-releasing cycles. Additionally, the strain sensor exhibited robust washing fastness under an ultrasonic time of 120 min at 240 W and 50 Hz. Furthermore, it had a superior sensing performance in monitoring joint motions of the human body. The high sensitivity and motion sensing performance presented here demonstrate that PDA@SEBS/MWNCTs yarn has great potential to be used as components of wearable devices

Tunable Near-Infrared Transparent Bands Based on Cascaded Fabry–Perot Cavities Containing Phase Change Materials

In this paper, we construct a near-infrared Fabry–Perot cavity composed of two sodium (Na) layers and an antimony trisulfide (Sb2S3) layer. By cascading two Fabry–Perot cavities, the transmittance peak splits into two transmittance peaks due to the coupling between two Fabry–Perot modes. We utilize a coupled oscillator model to describe the mode coupling and obtain a Rabi splitting of 60.0 meV. By cascading four Fabry–Perot cavities, the transmittance peak splits into four transmittance peaks, leading to a near-infrared transparent band. The near-infrared transparent band can be flexibly tuned by the crystalline fraction of the Sb2S3 layers. In addition, the effects of the layer thickness and incident angle on the near-infrared transparent band and the mode coupling are investigated. As the thickness of the Na layer increases, the coupling strength between the Fabry–Perot modes becomes weaker, leading to a narrower transparent band. As the thickness of the Sb2S3 layer increases, the round-trip propagating of the Sb2S3 layer increases, leading to the redshift of the transparent band. As the incident angle increases, the round-trip propagating of the Sb2S3 layer decreases, leading to the blueshift of the transparent band. This work not only provides a viable route to achieving tunable near-infrared transparent bands, but also possesses potential applications in high-performance display, filtering, and sensing

Biodegradable Polyurethane Fiber-Based Strain Sensor with a Broad Sensing Range and High Sensitivity for Human Motion Monitoring

To date, a majority of polymer-based wearable flexible strain sensors are non-biodegradable, which inevitably causes environmental pollution at the end of their service life. In this work, biodegradable polyurethane (BPU) was synthesized and then processed with carbon nanotubes (CNTs) via wet spinning into BPU/CNT composite fibers used as strain sensors. The synthesized BPU showed excellent biodegradability with a 19.45% weight loss in 42 days in a phosphate buffered saline (PBS) solution. Compared with previously reported strain sensors made from silk, cellulose, and polylactic acid, the BPU/12%CNT fibers achieved a much wider strain-sensing range (0–250%) and a high sensitivity (gauge factors of 15 at 100% strain and of 2468 at 250% strain respectively) while exhibiting reliable stability. These properties allow strain sensors based on BPU/CNT fibers and knitted fabric to be successfully used for monitoring various human motions. Moreover, biodegradability of the BPU/CNT strain sensor in a PBS solution was verified. In consequence, this work provides insights into the development of biodegradable wearable electronic devices