High versatility of polyethylene terephthalate (PET) waste for the development of batteries, biosensing and gas sensing devices.

Continuously growing adoption of electronic devices in energy storage, human health and environmental monitoring systems increases demand for cost-effective, lightweight, comfortable, and highly efficient functional structures. In this regard, the recycling and reuse of polyethylene terephthalate (PET) waste in the aforementioned fields due to its excellent mechanical properties and chemical resistance is an effective solution to reduce plastic waste. Herein, we review recent advances in synthesis procedures and research studies on the integration of PET into energy storage (Li-ion batteries) and the detection of gaseous and biological species. The operating principles of such systems are described and the role of recycled PET for various types of architectures is discussed. Modifying the composition, crystallinity, surface porosity, and polar surface functional groups of PET are important factors for tuning its features as the active or substrate material in biological and gas sensors. The findings indicate that conceptually new pathways to the study are opened up for the effective application of recycled PET in the design of Li-ion batteries, as well as biochemical and catalytic detection systems. The current challenges in these fields are also presented with perspectives on the opportunities that may enable a circular economy in PET use.

Selective Growth of Graphene-Confined Inkjet-Printed Sn Nanoparticles on Plastic Using Intense Pulsed Light Annealing.

Printing graphene-based nanomaterials on flexible substrates has become a burgeoning platform for next-generation technologies. Combining graphene and nanoparticles to create hybrid nanomaterials has been proven to boost device performance, thanks to their complementary physical and chemical properties. However, high growth temperatures and long processing times are often required to produce high-quality graphene-based nanocomposites. For the first time, we report a novel scalable approach for additive manufacturing of Sn patterns on polymer foil and their selective conversion into nanocomposite films under atmospheric conditions. A combination of inkjet printing and intense flashlight irradiation techniques is studied. Light pulses that are selectively absorbed by the printed Sn patterns cause a temperature of over 1000 °C to be reached locally in a split second without damaging the underlying polymer foil. The top surface of the polymer foil at the interface with printed Sn becomes locally graphitized and acts as a carbon source, transforming printed Sn into Sn@graphene (Sn@G) core-shell patterns. Our results revealed a decrease in electrical sheet resistance, with an optimal value (Rs = 72 ± 2 Ω/sq) reached when light pulses with an energy density of 12.8 J/cm2 were applied. These graphene-protected Sn nanoparticle patterns exhibit excellent resistance against air oxidation for months. Finally, we demonstrate the implementation of Sn@G patterns as electrodes for Li-ion microbatteries (LIBs) and triboelectric nanogenerators (TENGs), showing remarkable performance. This work offers new insight into the development of a versatile, eco-friendly, and cost-effective technique for producing well-defined patterns of graphene-based nanomaterials directly on a flexible substrate using different light-absorbing nanoparticles and carbon sources.

Toward autonomous wearable triboelectric systems integrated on textiles.

One of the major requirements of smart textiles is to achieve the integration of an energy source for powering embedded electronic systems. In this context, textile triboelectric nanogenerators (T-TENGs) are particularly well suited to imperceptibly play this role in the core of textiles, making them highly appealing for the development of future autonomous systems. This article reviews the wide range of topics related to T-TENGs technology starting from triboelectric generation (textile device and behavior modeling) up to the complete integration of power transfer (rectifier) circuits on textiles. The modeling part deals with the current mathematical models of the triboelectric charge transfer in order to highlight efficient power transfer circuits. Then the materials and architectures used to fabricate different types of T-TENGs are described. Finally, the methods and technologies to seamlessly integrate the power transfer circuit into textiles are discussed: from realizing electrically conductive tracks through to integrating electronic component on textiles.

Application of a conversion electrode based on decomposition derivatives of Ag4[Fe(CN)6] for aqueous electrolyte batteries.

The lack of stable electrode materials for water-based electrolytes due to the intercalation and conversion reaction mechanisms encourage scientists to design new or renovate existing materials with better cyclability, capacity, and cost-effectiveness. Ag4[Fe(CN)6] is a material belonging to the Prussian blue family that can be used, as its other family members, as an electrode material with the intercalation/deintercalation reaction or conversion-type mechanism through Ag oxidation/reduction. However, due to the instability of this material in its dry state, it decomposes to AgCN and a Prussian blue residual complex. A possible reason for Ag4[Fe(CN)6] decomposition is discussed. Nevertheless, it is shown that the decomposition products of Ag4[Fe(CN)6] have electrochemical activity due to the reversible oxidation/reduction of Ag atoms in water-based electrolytes.

Biomimetic models of the human eye, and their applications.

Replicating the functionality of the human eye has been a challenge for more than a century, creating a great wealth of biomimetic and bioinspired devices, and providing ever improving models of the eye for myriad research purposes. As improvements in microelectronics have proceeded, individual components of the eye have been replicated, and models of the optical behaviour of the eye have improved. This review explores both work developed for improving medical components, with an ultimate aim of a fully functioning prosthetic eye, and work looking at improving existing devices through biomimetic means. It is hoped that this holistic approach to the subject will aid in the cross pollination of ideas between the two research foci. The review starts by summarising the reported measurements of optical parameters of various components of the eye. It then charts the development of individual bionic components. Particular focus is put on the development of bionic and biomimetic forms of the two main adaptive components of the eye, namely the lens and the iris, and the challenges faced in modelling the light sensitive retina. Work on each of these components is thoroughly reviewed, including an overview of the principles behind the many different approaches used to mimic the functionality, and discussion of the pros and cons of each approach. This is concluded by an overview of several reported models of the complete or semi-complete eye, including details of the components used and a summary of the models' functionality. Finally, some consideration is given to the direction of travel of this field of research, and which existing approaches are likely to bring us closer to the long term goal of a fully functional analogue of the eye.

Changes in temperature inside an optomechanical model of the human eye during emulated transscleral cyclophotocoagulation.

Currently, many diseases of the eye are treated by laser surgery. An understanding of light propagation and the heating of eye tissue during laser exposure is crucial to improving the outcome of these procedures. Here, we present the development of physical and computational models of the human eye by combining optical light propagation and thermal characteristics. For the physical model, all parts of the eye, including cornea, lens, ciliary body, sclera, aqueous and vitreous humors, and iris, were fabricated using a 3D printed holder and modified polydimethylsiloxane. We also present a computational model based on finite element analysis that allows for a direct comparison between the simulation and experimental measurements. These models provide an opportunity to directly assess the rise in temperature in all eye tissues. The simulated and physical models showed good agreement for the transmission of light at varying incident angles. The heating of optical components was investigated in the retina and the ciliary body during simulated laser surgery. Temperature increases of 45.3°C and 30.6°C in the retina and ciliary bodies, respectively, were found in the physical model after 1 minute of exposure to 186 mW of 850 nm laser radiation. This compared to 29.8°C and 33.9°C increases seen under the same conditions in the simulation model with human eye parameters and 48.1°C and 28.7°C for physical model parameters. These results and these models are very promising for further investigation of the impact of laser surgery.

All-Solid-State Lithium Ion Batteries Using Self-Organized TiO2 Nanotubes Grown from Ti-6Al-4V Alloy.

All-solid-state batteries were fabricated by assembling a layer of self-organized TiO2 nanotubes grown on as anode, a thin-film of polymer as an electrolyte and separator, and a layer of composite LiFePO4 as a cathode. The synthesis of self-organized TiO2 NTs from Ti-6Al-4V alloy was carried out via one-step electrochemical anodization in a fluoride ethylene glycol containing electrolytes. The electrodeposition of the polymer electrolyte onto anatase TiO2 NTs was performed by cyclic voltammetry. The anodized Ti-6Al-4V alloys were characterized by scanning electron microscopy and X-ray diffraction. The electrochemical properties of the anodized Ti-6Al-4V alloys were investigated by cyclic voltammetry and chronopotentiometry techniques. The full-cell shows a high first-cycle Coulombic efficiency of 96.8% with a capacity retention of 97.4% after 50 cycles and delivers a stable discharge capacity of 63 µAh cm-2 µm-1 (119 mAh g-1) at a kinetic rate of C/10.

TiO2 Nanotube Layers Decorated with Al2O3/MoS2/Al2O3 as Anode for Li-ion Microbatteries with Enhanced Cycling Stability.

TiO2 nanotube layers (TNTs) decorated with Al2O3/MoS2/Al2O3 are investigated as a negative electrode for 3D Li-ion microbatteries. Homogenous nanosheets decoration of MoS2, sandwiched between Al2O3 coatings within self-supporting TNTs was carried out using atomic layer deposition (ALD) process. The structure, morphology, and electrochemical performance of the Al2O3/MoS2/Al2O3-decorated TNTs were studied using scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and chronopotentiometry. Al2O3/MoS2/Al2O3-decorated TNTs deliver an areal capacity almost three times higher than that obtained for MoS2-decorated TNTs and as-prepared TNTs after 100 cycles at 1C. Moreover, stable and high discharge capacity (414 µAh cm-2) has been obtained after 200 cycles even at very fast kinetics (3C).

Direct Pre-lithiation of Electropolymerized Carbon Nanotubes for Enhanced Cycling Performance of Flexible Li-Ion Micro-Batteries.

Carbon nanotubes (CNT) are used as anodes for flexible Li-ion micro-batteries. However, one of the major challenges in the growth of flexible micro-batteries with CNT as the anode is their immense capacity loss and a very low initial coulombic efficiency. In this study, we report the use of a facile direct pre-lithiation to suppress high irreversible capacity of the CNT electrodes in the first cycles. Pre-lithiated polymer-coated CNT anodes displayed good rate capabilities, studied up to 30 C and delivered high capacities of 850 mAh g-1 (313 µAh cm-2) at 1 C rate over 50 charge-discharge cycles.

Determination of optical parameters of the porcine eye and development of a simulated model.

The eye is a very sophisticated system of optical elements for the preeminent sense of vision. In recent years, the number of laser surgery to correct the optical aberration such as myopia or astigmatism has significantly increased. Consequently, improving the knowledge related to the interactions of light with the eye is very important in order to enhance the efficiency of the surgery. For this reason, a complete optical characterization of the porcine eye is presented in this study. Kubelka-Munk and Inverse Adding-Doubling methods were applied to spectroscopy measurement to determine the absorption and scattering coefficients. Furthermore, the refractive index has been measured by ellipsometry. The different parameters were obtained for the cornea, lens, vitreous humor, sclera, iris, choroids and eyelid in the visible and infrared region. Thereafter, the results are implemented in a COMSOL Multiphysics® software to create an eye model. This model gives a better understanding of the propagation of light in the eye by adding optical parts such as the iris, the sclera or the ciliary bodies. Two simulations show the propagation of light from the cornea to the retina but also from the sclera to the retina. This last possibility provides a better understanding of light propagation during eye laser surgery such as, for example, transscleral cyclophotocoagulation. Figure: Eye simulation models allow the development of new laser treatments in a simple and safe way for patients. To this purpose, the creation of an eye simulated model based on optical parameters obtained from experimental data is presented in this study. This model will facilitate the understanding of the light propagation inside the porcine eye.

Flexible Micro-Battery for Powering Smart Contact Lens.

In this paper, we demonstrate the first attempt of encapsulating a flexible micro battery into a contact lens to implement an eye-tracker. The paper discusses how to scale the battery to power various circuits embedded in the contact lens, such as ASIC, photodiodes, etc., as well as how to combine the battery with external harvested energy sources. The fabricated ring battery has a surface area of 0.75 cm2 yielding an areal capacity of 43 µAh·cm-2 at 20C. Based on simulated 0.35-µm CMOS ASIC power consumption, this value is large enough to allow powering the ASIC for 3 minutes. The functioning of the micro battery is demonstrated by powering an orange LED.

Superior Electrochemical Performance of Thin-Film Thermoplastic Elastomer-Coated SnSb as an Anode for Li-ion Batteries.

The high failure strain of thermoplastic elastomers (TPEs) is a very desirable feature for rechargeable Li-ion batteries by improving the lifetime of high specific capacity anode materials that undergo mechanical fractures induced by large volume variations. In this work, poly(styrene-b-2-hydroxyethyl acrylate) called PS-b-PHEA was synthesized by a nitroxide meditated polymerization method. Owing to the use of a specific polystyrene macroinitiator (SG1), a suitable TPE copolymer with long hydroxyethyl acrylate blocks to ensure good mechanical properties is obtained for the first time. We show that the electrochemical properties of the PS-b-PHEA-coated SnSb anode are drastically improved by suppressing the crack formation at the surface of the electrode. Indeed, electrochemical characterization revealed that a high and stable gravimetric capacity over 100 cycles could be achieved. Moreover, excellent capacity reversibility was achieved when cycled at multiple C-rates and fast kinetics confirming the strong protection role of the polymer. The advanced chemical and mechanical properties of PS-b-PHEA open up promising perspectives to significantly improve the electrochemical performance of all electrodes that are known to suffer from large volume variations.

Optical and Electrochemical Properties of Self-Organized TiO2 Nanotube Arrays From Anodized Ti-6Al-4V Alloy.

Due to their high specific surface area and advanced properties, TiO2 nanotubes (TiO2 NTs) have a great significance for production and storage of energy. In this paper, TiO2 NTs were synthesized from anodization of Ti-6Al-4V alloy at 60 V for 3 h in fluoride ethylene glycol electrolyte by varying the water content and further annealing treatment. The morphological, structural, optical and electrochemical performances of TiO2 NTs were investigated by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), UV-Visible spectroscopy and electrochemical characterization techniques. By varying the water content in the solution, a honeycomb and porous structure was obtained at low water content and the presence of (α + ß) phase in Ti-6Al-4V alloy caused not uniform etching. With an additional increase in water content, a nanotubular structure is formed in the (α + ß) phases with different morphological parameters. The anatase TiO2 NTs synthesized with 20 wt% H2O shows an improvement in absorption band that extends into the visible region due the presence of vanadium oxide in the structure and the effective band gap energy (Eg) value of 2.25 eV. The TiO2 NTs electrode also shows a good cycling performance, delivering a reversible capacity of 82 mAh.g-1 (34 µAh.cm-2.µm-1) at 1C rate over 50 cycles.

Electrodeposition of Polymer Electrolyte Into Porous LiNi0.5Mn1.5O4 for High Performance All-Solid-State Microbatteries.

We report the electrodeposition of polymer electrolyte (PMMA-PEG) in porous lithium nickel manganese oxide (LiNi0.5Mn1.5O4) cathode layer by cyclic voltammetry. The cathode-electrolyte interface of the polymer-coated LNMO electrode has been characterized by scanning electron microscopy and electrochemical techniques. Electrochemical measurements consisting of galvanostatic cycling tests and electrochemical impedance spectroscopy revealed a significant improvement of the capacity values and the increase of the operating voltage. These effects are attributed to the total filling of pores by the electrodeposited polymer that contributes to improve the reversible insertion of Li+. A complete all-solid-state microbattery consisting of electropolymerized LNMO as the cathode, a thin polymer layer as the electrolyte, and TiO2 nanotubes as the anode has been successfully fabricated and tested.

ALD Al2O3-Coated TiO2 Nanotube Layers as Anodes for Lithium-Ion Batteries.

The utilization of the anodic TiO2 nanotube layers, with uniform Al2O3 coatings of different thicknesses (prepared by atomic layer deposition, ALD), as the new electrode material for lithium-ion batteries (LIBs), is reported herein. Electrodes with very thin Al2O3 coatings (∼1 nm) show a superior electrochemical performance for use in LIBs compared to that of the uncoated TiO2 nanotube layers. A more than 2 times higher areal capacity is received on these coated TiO2 nanotube layers (∼75 vs 200 µAh/cm2) as well as higher rate capability and coulombic efficiency of the charging and discharging reactions. Reasons for this can be attributed to an increased mechanical stability of the TiO2 nanotube layers upon Al2O3 coating, as well as to an enhanced diffusion of the Li+ ions within the coated nanotube layers. In contrast, thicker ALD Al2O3 coatings result in a blocking of the electrode surface and therefore an areal capacity decrease.

Bottom-Up Electrochemical Deposition of Poly(styrene sulfonate) on Nanoarchitectured Electrodes.

The cathodic deposition of poly(styrene sulfonate) on nanoarchitectured TiO2 electrodes is explored by cyclic voltammetry and potentiostatic and galvanostatic experiments, showing a diffusion-controlled deposition described by Cottrell's law. The structure and composition of the polymer is evidenced by various spectroscopic techniques, including nuclear magnetic resonance, Fourier transform infrared, and X-ray photoelectron spectroscopy, and its morphology is studied by scanning electron microscopy. The average chain length can be estimated from the NMR spectra. The electropolymerization mechanism initiates by radical anion formation. The cycling behavior in half-cell batteries against Li metal is excellent, especially at high rates explored up to 10 C. The areal insertion capacity is above recent literature results, up to 80 µA h cm-2. The combination of normalized areal power density and areal energy density is one of the best reported in the literature.

Porous NASICON-Type Li3Fe2(PO4)3 Thin Film Deposited by RF Sputtering as Cathode Material for Li-Ion Microbatteries.

We report the electrochemical performance of porous NASICON-type Li3Fe2(PO4)3 thin films to be used as a cathode for Li-ion microbatteries. Crystalline porous NASICON-type Li3Fe2(PO4)3 layers were obtained by radio frequency sputtering with an annealing treatment. The thin films were characterized by XRD, SEM, and electrochemical techniques. The chronoamperometry experiments showed that a discharge capacity of 88 mAhg(-1) (23 µAhcm(-2)) is attained for the first cycle at C/10 to reach 65 mAhg(-1) (17 µAhcm(-2)) after 10 cycles with a good stability over 40 cycles.

Anodized Ti3SiC2 As an Anode Material for Li-ion Microbatteries.

We report on the synthesis of an anode material for Li-ion batteries by anodization of a common MAX phase, Ti3SiC2, in an aqueous electrolyte containing hydrofluoric acid (HF). The anodization led to the formation of a porous film containing anatase, a small quantity of free carbon, and silica. By varying the anodization parameters, various oxide morphologies were produced. The highest areal capacity was achieved by anodization at 60 V in an aqueous electrolyte containing 0.1 v/v HF for 3 h at room temperature. After 140 cycles performed at multiple applied current densities, an areal capacity of 380 µAh·cm(-2) (200 µA·cm(-2)) has been obtained, making this new material, free of additives and binders, a promising candidate as a negative electrode for Li-ion microbatteries.

Porous Silicon Nanotube Arrays as Anode Material for Li-Ion Batteries.

We report the electrochemical performance of Si nanotube vertical arrays possessing thin porous sidewalls for Li-ion batteries. Porous Si nanotubes were fabricated on stainless steel substrates using a sacrificial ZnO nanowire template method. These porous Si nanotubes are stable at multiple C-rates. A second discharge capacity of 3095 mAh g(-1) with a Coulombic efficiency of 63% is attained at a rate of C/20 and a stable gravimetric capacity of 1670 mAh g(-1) obtained after 30 cycles. The high capacity values are attributed to the large surface area offered by the porosity of the 3D nanostructures, thereby promoting lithium-ion storage according to a pseudocapacitive mechanism.