A study of flexible supercapacitors: design, manufacture and testing

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonSupercapacitors have attracted great attention because of their high power density, long life cycle and high efficiency. They can be generally classified into two types: electrical double-layer capacitors (EDLCs) and pseudocapacitors. Compared with pseudocapacitors, EDLCs have a very fast charge/discharge rate, higher power density, higher coulombic efficiency and longer cycle life. Recently, in order to meet the requirements of portable and wearable electronics, supercapacitor development is moving towards flexible and stretchable solutions. This thesis presents the design, fabrication, performance testing and optimisation of flexible strip and fibre EDLCs. In this research, a sandwich structured strip EDLC was designed and manufactured. Experimental design was utilised to optimise the operation parameters of the EDLC in order to improve its capacity for energy storage. The flexibility of the strip EDLCs was studied extensively by mechanical tests under static and dynamic loading conditions, and the correlation between the electrochemical performance of the EDLCs and the mechanical testing process was investigated. Novel coaxial fibre EDLCs have also been studied and developed in this study. Fibre supercapacitors showed a good flexibility and weavability. The activated carbon produced by ball-milling method with optimum specific capacitance was mixed with commercial ink to produce active material to optimise the electrochemical performance of fibre EDLCs. The flexible EDLCs were applied into different appliances to demonstrate the stability of performance and the usability of EDLCs developed in this study. The electrical current and potential range can be altered by connecting multiple strip or fibre EDLCs in parallel or in series to meet the power and energy requirements. It has been proved that the flexible EDLCs developed have a great potential to be used as energy storage devices for smart electronics. This thesis makes original contributions to knowledge, including using an advanced test method to study the electrochemical performance of flexible supercapacitors under static and dynamic mechanical testing, investigation of the effect of key parameters in the manufacturing process on the performance of strip supercapacitors using experimental design method to optimise the supercapacitors’ performance, and optimisation of the performance of fibre supercapacitors by improving the structure and using a new active material with higher specific capacitance

Experimental design to optimise electrical performance of strip supercapacitors

Strip shaped electric double-layer supercapacitors (EDLCs) using activated carbon as the electrode material have been successfully fabricated and optimised. Their electrochemical characteristics were studied using a VersaSTAT 3 electrochemical workstation. The experimental design software, JMP™, was used to optimise the main parameters of supercapacitors in order to maximise the electrical performance. Simultaneously, the relationship between the electrical performance and the key manufacturing factors of the EDLCs, including the binder content, the electrolyte concentration and the thickness of electrode materials was studied and discussed

A deep learning model for drug screening and evaluation in bladder cancer organoids

Three-dimensional cell tissue culture, which produces biological structures termed organoids, has rapidly promoted the progress of biological research, including basic research, drug discovery, and regenerative medicine. However, due to the lack of algorithms and software, analysis of organoid growth is labor intensive and time-consuming. Currently it requires individual measurements using software such as ImageJ, leading to low screening efficiency when used for a high throughput screen. To solve this problem, we developed a bladder cancer organoid culture system, generated microscopic images, and developed a novel automatic image segmentation model, AU2Net (Attention and Cross U2Net). Using a dataset of two hundred images from growing organoids (day1 to day 7) and organoids with or without drug treatment, our model applies deep learning technology for image segmentation. To further improve the accuracy of model prediction, a variety of methods are integrated to improve the model’s specificity, including adding Grouping Cross Merge (GCM) modules at the model’s jump joints to strengthen the model’s feature information. After feature information acquisition, a residual attentional gate (RAG) is added to suppress unnecessary feature propagation and improve the precision of organoids segmentation by establishing rich context-dependent models for local features. Experimental results show that each optimization scheme can significantly improve model performance. The sensitivity, specificity, and F1-Score of the ACU2Net model reached 94.81%, 88.50%, and 91.54% respectively, which exceed those of U-Net, Attention U-Net, and other available network models. Together, this novel ACU2Net model can provide more accurate segmentation results from organoid images and can improve the efficiency of drug screening evaluation using organoids

Hierarchical Honeycomb-structured Electret/Triboelectric Nanogenerator for Biomechanical and Morphing Wing Energy Harvesting

Flexible, compact, lightweight and sustainable power sources are indispensable for modern wearable and personal electronics and small-unmanned aerial vehicles (UAVs). Hierarchical honeycomb has the unique merits of compact mesostructures, excellent energy absorption properties and considerable weight to strength ratios. Herein, a honeycomb-inspired triboelectric nanogenerator (h-TENG) is proposed for biomechanical and UAV morphing wing energy harvesting based on contact triboelectrification wavy surface of cellular honeycomb structure. The wavy surface comprises a multilayered thin film structure (combining polyethylene terephthalate, silver nanowires and fluorinated ethylene propylene) fabricated through high-temperature thermoplastic molding and wafer-level bonding process. With superior synchronization of large amounts of energy generation units with honeycomb cells, the manufactured h-TENG prototype produces the maximum instantaneous open-circuit voltage, short-circuit current and output power of 1207 V, 68.5 μA and 12.4 mW, respectively, corresponding to a remarkable peak power density of 0.275 mW/cm3 (or 2.48 mW/g) under hand-pressing excitations. Attributed to the excellent elastic property of self-rebounding honeycomb structure, the flexible and transparent h-TENG can be easily pressed, bent, and integrated into shoes for real-time insole plantar pressure mapping. The lightweight and compact h-TENG is further installed into a morphing wing of small UAVs for efficiently converting the flapping energy of ailerons into electricity for the first time. This research demonstrates this new conceptualizing single h-TENG device's versatility and viability for broad-range real-world application scenarios

A Solid-State Wire-Shaped Supercapacitor Based on Nylon/Ag/Polypyrrole and Nylon/Ag/MnO₂ Electrodes

In this work, a novel wire-shaped supercapacitor based on nylon yarn with a high specific capacitance and energy density was developed by designing an asymmetric configuration and integrating pseudocapacitive materials for both electrodes. The nylon/Ag/MnO2 yarn was prepared as a positive electrode by electrochemically depositing MnO2 on a silver-paste-coated nylon yarn. Additionally, PPy was prepared on nylon/Ag yarn by chemical polymerization firstly to enlarge the surface roughness of nylon/Ag, and then the PPy could be easily coated on the chemically polymerized nylon/Ag/PPy by electrochemical polymerization to obtain a nylon/Ag/PPy yarn-shaped negative electrode. The wire-shaped asymmetric supercapacitor (WASC) was fabricated by assembling the nylon/Ag/MnO2 electrode, nylon/Ag/PPy electrode and PAANa/Na2SO4 gel electrolyte. This WASC showed a wide potential window of 1.6 V and a high energy density varying from 13.9 to 4.2 μWh cm−2 with the corresponding power density changing from 290 to 2902 μW cm−2. Meanwhile, because of the high flexibility of the nylon substrate and superior adhesion of active materials, the WASC showed a good electrochemical performance stability under different bending conditions, suggesting its good flexibility. The promising performance of this novel WASC is of great potential for wearable/portable devices in the future

A Flexible Wearable Antenna with Annular Solar Eclipse Structure for ISM/WLAN/WIMAX/Bluetooth Applications

This paper proposes a wearable flexible dual-band antenna that covers the 2.34–2.68 GHz and 4.05–5.26 GHz frequency bands. This antenna employs a novel nested imitation annular solar eclipse structure, where the main radiator is a gradually widening loop, and another loop is coupled inside the radiator. The antenna, with overall dimensions of 40∗32∗0.3 mm³, utilizes polyimide as the dielectric material. The gain, efficiency, and cross-polarization of the antenna were tested using a microwave anechoic chamber. The antenna achieves a maximum gain of 6 dBi and a maximum efficiency of 79.6%. We tested the SAR of the antenna at 10 mm from the human body, which was significantly below the international standard of 2.0 W/kg. The flexible antenna presented in this paper exhibits a broad low-frequency bandwidth, enabling coverage of various communication bands such as ISM, WLAN, WIMAX, and Bluetooth. The antenna delivers satisfactory simulation and measurement results while meeting the requirements of minimizing radiation exposure to the human body

Liposome Lipid-Based Formulation Has the Least Influence on rAAV Transduction Compared to Other Transfection Agents

Recombinant adeno-associated virus (rAAV) vectors are considered ideal vehicles for human gene therapy. Meanwhile, non-viral strategies, such as transfection agents (TAs), have also shown promise to deliver genetic materials, such as siRNA. Transduction with the rAAV vector is performed concurrently with transfection with plasmid DNA or RNA. In the present study, we report that various TAs inhibited rAAV-mediated transgene expression at diverse levels. Overall, cationic polymers and dendrimers dramatically blocked rAAV transduction, while lipid-based liposomes displayed the least effect. The inhibitory effect was dependent on the dose of TAs and the timing of infection, suggesting that the early stages of viral infection were involved. In addition, the present results indicate that the transgene expression of rAAV vectors was significantly increased by liposome-mediated transfection with adenoviral helper genes. At the same time, this was dramatically inhibited by liposome-mediated transfection with the trichosanthin gene encoding a type I ribosome-inactivating protein isolated from traditional Chinese medicine. Furthermore, liposomes also have little effect on rAAV-mediated transgene expression in vivo. Taken together, these findings suggest liposome as the best choice of TAs, which should be used in combination with rAAV-mediated gene therapy. Keywords: liposome lipid-based formulation, rAAV, transduction, transfection agents, trichosanthi

A Wearable Self-Grounding Slit Antenna for ISM/4G/5G/Bluetooth/WLAN Applications

This design proposes a self-grounding semi-circular gap dual-band flexible antenna in the context of the rapid development of wireless body area networks. The antenna combines the slit structure with the characteristics of traditional rectangular monopole antenna to realize dual-band. In addition, the antenna’s grounding structure adopts the self-grounding structure, which is less used nowadays, to extend the bandwidth. The antenna is designed on a dielectric board of polyimide material with a relative dielectric constant of 3.5. The overall dimensions of the antenna are 44 mm $\times 40$ mm $\times 0.2$ mm with two different sized gaps in a rectangular patch, similar to the geometry of an umbrella handle. Measured data shows that the structure has higher gain and efficiency in the bent state than in the flat state, making it ideal for wearable smart terminals. It can be combined with a smart armband for sports and medical applications or for a single soldier wearable wristband smartwatch. The article explores the effect of different slot sizes and different bending angles on the performance of the antenna, as well as the specific absorption rate values of the antenna for the human body. Finally, two frequency bands with good omnidirectional radiation characteristics are obtained: 2.38–2.81 GHz and 4.28–5.10 GHz. The antenna covers ISM, 4G, 5G, Bluetooth, WLAN, and other common communication frequency bands. The results of the study show that the design method is highly reliable

Robust State Estimation Method Based on Mahalanobis Distance Under Non-Gauss Noise

Under non-Gauss noise condition, the performance of traditional state estimation methods based on Gauss measurement noise will be greatly reduced. In order to solve this problem, a robust state estimation method based on Mahalanobis distance under non-Gauss noise is proposed in this paper. First of all, based on the Mahalanobis distance, the calculation method of optimal buffer length for PMU measurements is used, which can unify the SCADA measurements with PMU measurements in the same snapshot. Then, Based on the two-stage processing method, in the first stage, the SCADA measurements are used for filtering by using maximum likelihood estimator to obtain the estimated values, and then the estimated values in the first-stage are combined with PMU measurements as the second-stage measurements for filtering, and finally the final results are obtained. Based on the IEEE-39 buses system and IEEE-118 buses system, under Gaussian noise and non-Gaussian noise, the AEE results of proposed method are very small, and which are all within 10−3, numerical tests under different simulation conditions verified the robustness and effectiveness