Electrically Adaptive and Shape-Changeable Invertible Microlens

Plasticized polyvinyl chloride: From material properties to flexible applications

The development of electroactive polymers (EAPs) affords novel integrated actuation and sensing technologies for intelligent flexible systems, enabling them to achieve remarkable flexibility and intelligence. Among EAPs, plasticized polyvinyl chloride (PVC) gel stands out as an ideal candidate for next-generation intelligent flexible applications due to its combination of exceptional actuation and sensing properties. This paper presents a comprehensive overview of recent advances in PVC gel actuators and sensors, including fabrication, properties, modeling, and applications. In particular, the outstanding actuation and sensing properties of PVC gel are thoroughly analyzed to exhibit its immense potential for application in smart flexible devices. Furthermore, the inherent relationships between the properties and materials of PVC gel are further revealed. Moreover, recent modification techniques to enhance the actuation and sensing properties of PVC gel are summarized, offering guidance for improving its properties. The current challenges and promising perspectives for enhancing performance and facilitating applications are finally discussed. We believe this paper will inspire the development of high-performance flexible devices employing PVC gel, as well as other EAPs, thereby paving the way for their practical applications.

Electrochemically mutable soft metasurfaces

Active optical metasurfaces, capable of dynamically manipulating light in ultrathin form factors, enable novel interfaces between humans and technology. In such interfaces, soft materials bring many advantages based on their flexibility, compliance and large stimulus-driven responses. Here, we create electrochemically mutable, soft metasurfaces that capitalize on the swelling of soft conducting polymers to alter the shape and associated resonant response of metasurface elements. Such geometric tuning overcomes the typical trade-off between achieving substantial tuning and low optical loss that is intrinsic to dynamic metasurfaces relying on index tuning of materials. Using the commercial polymer PEDOT:PSS, we demonstrate dynamic, high-resolution colour tuning and high-diffraction-efficiency (>19%) beam-steering devices that operate at CMOS-compatible voltages (~1.5 V). These results highlight how the deformability of soft materials can enable a class of high-performance metasurfaces that are suitable for body-worn technologies.

Electromechanical Performances of Polyvinyl Chloride Gels Using (Polyvinyl Chloride-Co-Vinyl Acetate) (P(VC-VA)) Synergistic Plasticization

The current polyvinyl chloride (PVC) gel flexible actuators are facing challenges of high input voltage and an insufficient elastic modulus. In this study, we conducted a detailed study on the properties of PVC gel prepared by introducing the modifier polyvinyl chloride-vinyl acetate (P(VC-VA)). We compared a modified PVC gel with the traditional one in terms of the relative dielectric constant, mechanical modulus, and electromechanical actuation performance. Experimental results demonstrated that the introduction of P(VC-VA) enhanced the dielectric constant and reduced the driving electric field strength of PVC gels. The dielectric constant increased from 4.77 to 7.3. The electromechanical actuation performance increased by 150%. We employed the Gent model to fit the experimental results, and the actual experimental data aligned well with the expectations of the Gent model. The research results show that this type of plasticizing method effectively balanced the mechanical and electrical performance of PVC gels. This study summarizes the experimental results and performance analysis of PVC gels prepared using innovative plasticization methods, revealing the potential engineering applications of polymeric gels.

Novel Optofluidic Imaging System Integrated with Tunable Microlens Arrays

Optofluidic tunable microlens arrays (MLAs) can manipulate and control light propagation using fluids. Lately, their applicability to miniature lab-on-a-chip systems is being extensively researched. However, it is difficult to incorporate 3D MLAs directly in a narrow microfluidic channel using common techniques. This has resulted in limited research on variable focal length imaging with optofluidic 3D MLAs. In this paper, we propose a method for fabricating MLAs in polydimethylsiloxane (PDMS)-based microchannels via electrohydrodynamic jet (E-jet) printing to achieve optofluidic tunable MLAs. Using this method, MLAs of diameters 15 to 80 μm can be fabricated in microfluidic channels with widths of 200 and 300 μm. By alternately using solutions with different refractive indices in the microchannel, the optofluidic microlenses exhibit reversible modulation properties while retaining the morphologies and refractive indices of the microlenses. The focal length of the resulting optofluidic chip can have threefold tunability, thereby achieving an imaging depth of approximately 450 μm. This outstanding advantage is useful in observing microspheres and cells flowing in the microfluidic system. Thus, the proposed optofluidic chip exhibits great potential for cell counting and imaging applications.

A novel electroactive plasticized polymer actuator based on chlorinated polyvinyl chloride gel

Plasticized poly (vinyl chloride) (PVC) gel is a promising electroactive polymer material for soft actuators and sensors, and it has attracted extensive attention and interest in multi-disciplinary fields. Chlorinated polyvinyl chloride (CPVC) has enhanced mechanical and chemical properties and shows a promising potential for fabricating gel materials for electroactive polymer gel actuators. Thus, we proposed a novel soft actuator based on CPVC gels. We studied the properties of CPVC gels with various technologies, such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) analysis, thermogravimetric analysis (TGA), etc. Furthermore, CPVC gel actuators were fabricated and the influence of membrane thickness and plasticizer content on the basic characteristics was investigated. The experimental results show that the CPVC gel actuator with a higher content of DBA has a better strain than that of the actuator with lower amount of DBA despite the membrane thickness. With the same ratio of DBA, the CPVC gel actuator has a better performance than the traditional PVC gel actuator under a low applied load. The maximum strain and stress of the CPVC gel (CPVC : DBA = 1 : 2.5) actuator are 9% and 0.12 MPa respectively at 400 V, which reaches the same level of the PVC gel actuator with higher content of DBA (PVC : DBA = 1 : 4). These results demonstrate a good potential of the proposed CPVC gel soft actuator for practical application.