Enhanced Electromechanical Property of Silicone Elastomer Composites Containing TiO2@SiO2 Core-Shell Nano-Architectures

Dielectric elastomer (DE) is one type of promising field-activated electroactive polymer. However, its significant electromechanical actuated properties are always obtained under a giant electric voltage, which greatly restricts the potential applications of DE. In the present work, the well-constructed core-shell TiO2@SiO2 nanoparticles were fabricated by using the classical Stöber method. A series of TiO2@SiO2 nano-architectures-filled polydimethylsiloxane (PDMS) composites were prepared via solution blending and compression-molding procedures. Benefiting from the additional SiO2 shell, both the interfacial compatibility between fillers and matrix and core-shell interfacial interaction can be improved. The TiO2@SiO2/PDMS nanocomposites exhibit a significantly enhanced in-plane actuated strain of 6.08% under a low electric field of 30 V·μm−1 at 16 vol.% TiO2@SiO2 addition, which is 180% higher than that of neat PDMS. The experimental results reveal that the well-designed core-shell structure can play an important role in both improving the electromechanical actuated property and maintaining a good flexibility of DE composites. This research provides a promising approach for the design of the novel composites with advanced low-field actuated electromechanical property in next generation DE systems.

Fabrication of Macroporous Nafion Membrane from Silica Crystal for Ionic Polymer-Metal Composite Actuator

Nafion membrane with macropores is synthesized from silica crystal and composited with Pt nanoparticles to fabricate macroporous ionic polymer-metal composite (M-IPMC) actuator. M-IPMC shows highly dispersed small Pt nanoparticles on the porous walls of Nafion membrane. After the electromechanical performance test, M-IPMC actuator demonstrates a maximum displacement output of 19.8 mm and a maximum blocking force of 8.1 mN, far better than that of IPMC actuator without macroporous structure (9.6 mm and 2.8 mN) at low voltages (5.8–7.0 V). The good electromechanical performance can be attributed to interconnected macropores that can improve the charge transport during the actuation process and can allow the Pt nanoparticles to firmly adsorb, leading to a good electromechanical property.

Flexopiezoelectricity at ferroelastic domain walls in WO3 films

The emergence of a domain wall property that is forbidden by symmetry in bulk can offer unforeseen opportunities for nanoscale low-dimensional functionalities in ferroic materials. Here, we report that the piezoelectric response is greatly enhanced in the ferroelastic domain walls of centrosymmetric tungsten trioxide thin films due to a large strain gradient of 106 m−1, which exists over a rather wide width (~20 nm) of the wall. The interrelationship between the strain gradient, electric polarity, and the electromechanical property is scrutinized by detecting of the lattice distortion using atomic scale strain analysis, and also by detecting the depolarized electric field using differential phase contrast technique. We further demonstrate that the domain walls can be manipulated and aligned in specific directions deterministically using a scanning tip, which produces a surficial strain gradient. Our findings provide the comprehensive observation of a flexopiezoelectric phenomenon that is artificially controlled by externally induced strain gradients.

Characterisation, Design and Experimentation of a Fabric Based Wearable Joint Sensing Device

The use of conductive fabrics (CF) in the design of wearables for joint sensing has recently received much interest in a wide range of applications such as robotics, rehabilitation, personal wellness, sports, and entertainment. In this paper, we evaluate a new wearable device concept that comprises of a CF strain-voltage sensor embedded as part of an inverted slider-crank mechanism for joint extension sensing. This has the benefit of not requiring anthropometric information from the user to related the joint parameters to the fabric strain readings, as opposed to an existing design. Firstly, we characterize the electromechanical property of a commercially available CF. Secondly, we formulate the geometric synthesis procedure of the joint sensing device as a constrained revolute joint system, where the CF is designed and introduced as an RPR chain to obtain an inverted slider-crank linkage. Lastly, we develop and validate our wearable joint sensing device against an experimental setup that represents an elbow joint. Our concept shows that our proposed joint sensing device can track the elbow extension motion of 140° with a maximum error of 7.66%.

Highly Stretchable Dry Electrode Composited with Carbon Nanofiber (CNF) for Wearable Device

In this work, we present a highly stretchable dry electrode composited with carbon nanofiber (CNF) for wearable device by simple method. The fabricated electrodes were assembled with snap connector for connect with electric circuit and sticky polymer for improving adhesion strength on the skin. We evaluated the electrical and mechanical properties depending on the weight % (wt%) and thickness of CNF/elastomer composited stretchable electrode. From the results, the electrical characteristic was improved as increasing concentrations of CNF and their dropping volume. And we evaluated a stretchability and electromechanical property using with cycling test. Through these tests, we have demonstrated that fabricated dry electrode has outstanding stretchability and durability under stretching condition. Finally, electrocardiogram (ECG) was measured with these electrodes. The results of ECG measurement showed similar or larger signal that of commercial wet electrode. Consequently, these results are expected to apply as a wearable device such as a bio-signal measurement and strain sensors.