Finding a perfect match of ion-exchanger and plasticizer for ion-selective sensors

Application of neutral ionophore based ion-selective sensors requires presence of ion-exchanger in the receptor phase, silently assuming that it is not only soluble but also dissociates to ions in the applied plasticizer. Although for typically applied ion-selective membrane constituents (plasticizers - ion-exchanger pairs) dissociation of ion-exchangers to ions is proven by theoretical (or close to) performance of resulting sensors, search for alternative plasticizers or ion-exchangers requires a method allowing estimation of the match of properties of involved compounds. In this work we propose a simple optical approach allowing estimation of ion-exchanger interactions with plasticizer. The results were confirmed by conductivity studies of model plasticizers solutions. The estimated dissociation constants of model ion-exchangers in plasticizers used are in excellent agreement with the results of optical studies. It was shown that solubility coupled with poor dissociation to ions of ion-exchanger affects performance of the resulting ion-selective membrane. Rational choice of properties of ion-exchanger and plasticizer allows finding a perfect match of the two, that results in improvements in performance of sensors (e.g. detection limits). As model sensors potassium and sodium ion-selective electrodes with poly(vinyl chloride) (PVC) based membranes, plasticized with classical plasticizer bis(2-ethylhexyl sebacate) or biodegradable alternative acetyl tributyl citrate, were prepared and studied using selected ion-exchangers.

Variable-focus liquid lens based on electrically responsive fluid

In this work, an adaptive liquid lens using a novel transparent electrically responsive fluid, dibutyl adipate (DBA), is demonstrated. The DBA liquid lens with a hemispherical plano-convex shape can change its curvature according to the application of various input voltages. More specifically, when an external direct current (DC) electric field is applied to the DBA liquid, the charges that are injected from the cathode move along with the DBA molecules toward the anode and accumulate on the surface of the anode. When the DC electric field is removed, the shape of the DBA liquid is recovered to its original state. This electrostatic force induces the deformation of the DBA liquid lens within a concentric annular anode electrode. In addition, the focal length of our system is increased from a value of approximately 7.5 mm to 13.1 mm when the voltage is changed from 0 to 100 V. Interestingly, the resolution of our DBA liquid lens can reach a value of ∼28.5 lp/mm. The proposed DBA liquid lens exhibits high optical transmittance (∼95%), good thermal stability (20-100°C), simple structure, and an excellent imaging property, which implies that the DBA liquid is a promising candidate for fabricating novel adaptive liquid lenses.

Investigation of a Novel Ecofriendly Electrolyte-Solvent for Lithium-Ion Batteries with Increased Thermal Stability

This study presents tributyl acetylcitrate (TBAC) as a novel ecofriendly high flash point and high boiling point solvent for electrolytes in lithium-ion batteries. The flash point (TFP=217∘C) and the boiling point (TBP=331∘C) of TBAC are approximately 200 K greater than that of conventional linear carbonate components, such as ethyl methyl carbonate (EMC) or diethyl carbonate (DEC). The melting point (TMP=−80∘C) is more than 100 K lower than that of ethylene carbonate (EC). Furthermore, TBAC is known as an ecofriendly solvent from other industrial sectors. A life cycle test of a graphite/NCM cell with 1 M lithium hexafluorophosphate (LiPF6) in TBAC:EC:EMC:DEC (60:15:5:20 wt) achieved a coulombic efficiency of above 99% and the remaining capacity resulted in 90 percent after 100 cycles (C/4) of testing. As a result, TBAC is considered a viable option for improving the thermal stability of lithium-ion batteries.

Electrically Tunable Lenses: A Review

Optical lenses with electrically controllable focal length are of growing interest, in order to reduce the complexity, size, weight, response time and power consumption of conventional focusing/zooming systems, based on glass lenses displaced by motors. They might become especially relevant for diverse robotic and machine vision-based devices, including cameras not only for portable consumer electronics (e.g. smart phones) and advanced optical instrumentation (e.g. microscopes, endoscopes, etc.), but also for emerging applications like small/micro-payload drones and wearable virtual/augmented-reality systems. This paper reviews the most widely studied strategies to obtain such varifocal “smart lenses”, which can electrically be tuned, either directly or via electro-mechanical or electro-thermal coupling. Only technologies that ensure controllable focusing of multi-chromatic light, with spatial continuity (i.e. continuous tunability) in wavefronts and focal lengths, as required for visible-range imaging, are considered. Both encapsulated fluid-based lenses and fully elastomeric lenses are reviewed, ranging from proof-of-concept prototypes to commercially available products. They are classified according to the focus-changing principles of operation, and they are described and compared in terms of advantages and drawbacks. This systematic overview should help to stimulate further developments in the field.

Electrically Adaptive and Shape-Changeable Invertible Microlens

Existing soft actuators for adaptive microlenses suffer from high required input voltage, optical loss, liquid loss, and the need for assistant systems. In this study, we fabricate a polyvinyl chloride-based gel using a new synergistic plasticization method to achieve simultaneously a high optical transparency and an ultrasoft rubber-like elastic behavior with a large voltage-induced deformation under a weak electric field. By compressing the smooth gel between two sets of annular electrodes, a self-contained biconvex microlens is realized that is capable of considerable shape changes in the optical path. Each surface of the dual-curvature microlens can be independently adjusted to focus or scatter light to capture real or virtual images, yield variable focal lengths (+31.8 to -11.3 mm), and deform to various shapes to improve aberrations. In addition to simple fabrication, our microlens operates silently and consumes low power (0.52 mW), making it superior to existing microlenses.

Polyvinyl chloride gels microlens array with a well-controlled curvature obtained by solvent evaporation under DC electric fields

In this paper, polyvinyl chloride (PVC) gels microlens arrays (MLAs) with controllable curvatures were prepared by evaporation of the solvent under DC electric fields. In order to obtain these arrays, the PVC gel solution was first injected into the cofferdam of a ring array patterned electrode substrate. Upon polarization under DC electric field, the electric charge injected from the cathode was carried by the plasticizers towards the anode to accumulate on its surface. After complete evaporation of the solvent, the PVC gels formed stable MLAs. The focal length of the formed MLAs obtained after evaporation of the 100 µL PVC gel solvent under 30 V DC field was 8.68 mm. The focal length of the as-obtained PVC gel-based MLAs can be well-controlled by merely tuning the strength of the electric field or by changing the volume of the PVC gel solution. Thus, it can be concluded that the proposed methodology looks very promising for future fabrication of MLAs with uniform size in larger areas.

High-k Polymer Nanocomposite Materials for Technological Applications

Understanding the properties of small molecules or monomers is decidedly important. The efforts of synthetic chemists and material engineers must be appreciated because of their knowledge of how utilize the properties of synthetic fragments in constructing long-chain macromolecules. Scientists active in this area of macromolecular science have shared their knowledge of catalysts, monomers and a variety of designed nanoparticles in synthetic techniques that create all sorts of nanocomposite polymer stuffs. Such materials are now an integral part of the contemporary world. Polymer nanocomposites with high dielectric constant (high-k) properties are widely applicable in the technological sectors including gate dielectrics, actuators, infrared detectors, tunable capacitors, electro optic devices, organic field-effect transistors (OFETs), and sensors. In this short colloquy, we provided an overview of a few remarkable high-k polymer nanocomposites of material science interest from recent decades.

Fabrication of a High-Performance Bending Actuator Made with a PVC Gel

This paper proposes a small, transparent, electroactive and highly deformable poly vinyl chloride (PVC) gel-based bending actuator. The effect of the PVC molecular weight and plasticizer content on the performance of the bending actuator is investigated. Three PVCs are prepared with different molecular weights (low molecular weight: PVCL, 116,000; medium molecular weight: PVCM, 239,000; and high molecular weight: PVCH, 282,000) and mixed with plasticizers in various ratios to achieve the best performance of the bending actuator. Experiments are conducted to investigate the bending performance of the actuators based on the prepared PVC gels. Among the prepared actuators, the PVCH-based bending actuator shows the best performance (maximum bending angle: 180°, elapsed time: 3.15 s).

An Enhanced Soft Vibrotactile Actuator Based on ePVC Gel with Silicon Dioxide Nanoparticles

In this paper, we propose a soft vibrotactile actuator made by mixing silicon dioxide nanoparticles and plasticized PVC gel. The effect of the silicon dioxide nanoparticles in the plasticized PVC gel for the haptic performance is investigated in terms of electric, dielectric, and mechanical properties. Furthermore, eight soft vibrotactile actuators are prepared as a function of the content. Experiments are conducted to examine the haptic performance of the prepared eight soft vibrotactile actuators and to find the best weight ratio of the plasticized PVC gel to the nanoparticles. The experiments should show that the plasticized PVC gel with silicon dioxide nanoparticles improves the haptic performance of the plasticized PVC gel-based vibrotactile actuator, and the proposed vibrotactile actuator can create a variety of haptic sensations in a wide frequency range.

Enhanced Design of a Soft Thin-Film Vibrotactile Actuator Based on PVC Gel

We fabricated a soft thin-film vibrotactile actuator, which can be easily inserted into wearable devices, based on an electroactive PVC gel. One of the most important factors in fabricating a soft and thin vibrotactile actuator is to create vibrational force strong enough to stimulate human skin in a wide frequency range. To achieve this, we investigate the working principle of the PVC gel and suggest a new structure in which most of electric energy contributes to the deformation of the PVC gel. Due to this structure, the vibrational amplitude of the proposed PVC gel actuator could considerably increase (0.816 g (g = 9.8 m/s2) at resonant frequency). The vibrotactile amplitude is proportional to the amount of input voltage. It increased from 0.05 g up to 0.416 g with increasing applied voltages from 200 V to 1 kV at 1 Hz. The experimental results show that the proposed actuator can create a variety of haptic sensations.

Focus-tunable double convex lens based on non-ionic electroactive gel

We propose a focus-tunable double-convex (DCX) lens based on a non-ionic PVC (nPVC) gel to be used at close conjugates. The proposed lens is composed of an nPVC gel and two plates with electrodes. Each plate has a hole whose boundary and inner part are pasted with an electrode (anode) and has another ring shaped electrode (cathode) whose center point is the same as the hole's center. The gel is sandwiched between an upper plate and a lower plate, and it is bulged inward between the holes of two plates by applied pressure from the plates (double-convex lens shape). The lens's focal length changed from 3 mm to 24.5 mm with applied voltages from 0 V to 400 V. We also observed that the proposed lens's field-of-view decreased from 121.9 ° to 41.9 ° according to the applied voltages. The proposed lens brings additional benefit for users with higher transmittance (over 94%).

High-Performance PVC Gel for Adaptive Micro-Lenses with Variable Focal Length

This paper presents a bio-inspired adaptive micro-lens with electrically tunable focus made of non-ionic high-molecular-weight polyvinyl chloride (PVC) gel. The optical device mimics the design of the crystalline lens and ciliary muscle of the human eye. It consists of a plano-convex PVC gel micro-lens on Indium Tin Oxide (ITO) glass, confined with an annular electrode operating as an artificial ciliary muscle. Upon electrical activation, the electroactive adhesive force of the PVC gel is exerted on the annular anode electrode, which reduces the sagittal height of the plano-convex PVC gel lens, resulting in focal length variation of the micro-lens. The focal length increases from 3.8 mm to 22.3 mm as the applied field is varied from 200 V/mm to 800 V/mm, comparable to that of the human lens. The device combines excellent optical characteristics with structural simplicity, fast response speed, silent operation, and low power consumption. The results show the PVC gel micro-lens is expected to open up new perspectives on practical tunable optics.