Scalable Paper Supercapacitors for Printed Wearable Electronics

Novel Fe(II)-Based Supramolecular Film Prepared by Interfacial Self-Assembly of an Asymmetric Polypyridine Ligand and Its Electrochromic Performance

An asymmetric two-arm polypyridine ligand 4'-{4-[4-(2,2'-dipyridyl)phenyl]}-2,2':6',2'-terpyridine (TPY-Ph-BPY) with double coordination units was synthesized using the one-step Suzuki reaction. The metallic supramolecular film was subsequently obtained by the Fe2+-induced self-assembly method at the CHCl3-H2O interface, which displayed a distinct flat and continuous morphology. The supramolecular film-coated ITO electrode demonstrated a reversible electrochemical redox behavior with pronounced color changes between purple and light green. Its solid-state electrochromic device had an optical contrast (ΔT%) of 26.2% at λmax = 573 nm with balanced coloring (tc = 2.4 s) and bleaching (tb = 2.6 s) times and a high current efficiency of 507.8 cm2/C. Moreover, good cycling stability with a long-term reversible color change was observed beyond 900 cycles. These results suggested the promising potential of the TPY-Ph-BPY-Fe(II) supramolecular film for electrochromic applications.

Synergistic integration of energy harvesters and supercapacitors for enhanced performance

In this paper, it is integrated a piezoelectric energy harvester and a supercapacitor storage device on a flexible substrate with a connection through an innovative alternative current (AC) to direct current (DC) boosting power management system for wearable biosensors' power supply. Flexible substrates can conform to irregular surfaces or shapes, enabling energy harvesting and storage devices to be integrated into a variety of form factors, including curved or bendable surfaces. Having an integrated energy harvester and storage system ensures a reliable and portable power source, providing power autonomy. The proposed element was layer-by-layer design including silver electrode, polyvinylidene fluoride-trifluoroethylene/multiwall carbon nanotubes, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate: carbon nanotubes, aluminium oxide, graphene and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate: carbon nanotubes (Ag/PVDF-TrFE:MWCNT/PEDOT:PSS:CNT/Al2O3/Gr/PEDOT:PSS:CNT), prepared by spray coating. A voltage rectifier with a low-pass filter and a direct current to direct current (DC-DC) converter was used as a power management system and intermediate unit between the harvester and storage part of the element. The type of the electronic circuit is voltage-doubler rectifier. It was found that piezoelectric harvester can generates voltage with a magnitude of 2V at loading of 110 g/cm2@10 Hz and with the proposed electronic circuit can be determined the workability of the created element during repeated charging and discharging, without introducing interfering changes in the capacity. The behaviour of the supercapacitor part is dependent on the thickness of Al2O3 and demonstrates more favourable characteristics at the thicker film of 750 nm, where the charging time is short (6s), the voltage ripples are small (±0.50 mV), and the maximum output voltage after charging almost reached the input supply voltage (∼1.94 V output voltage at 2 V input voltage). In addition, it resists up to 15500 cycles and shows a stable retention capacitance of 1.63 mF. The devices retain their capacity at multiple bending (1000) to 93 % and 91 %, according to the aluminium oxide film thickness, which is suitable for wearable devices.

Biohybrid Energy Storage Circuits Based on Electronically Functionalized Plant Roots

Biohybrid systems based on plants integrate plant structures and processes into technological components targeting more sustainable solutions. Plants' biocatalytic machinery, for example, has been leveraged for the organization of electronic materials directly in the vasculature and roots of living plants, resulting in biohybrid electrochemical devices. Among other applications, energy storage devices were demonstrated where the charge storage electrodes were seamlessly integrated into the plant tissue. However, the capacitance and the voltage output of a single biohybrid supercapacitor are limited. Here, we developed biohybrid circuits based on functionalized conducting roots, extending the performance of plant based biohybrid energy storage systems. We show that root-supercapacitors can be combined in series and in parallel configuration, achieving up to 1.5 V voltage output or up to 11 mF capacitance, respectively. We further demonstrate that the supercapacitors circuit can be charged with an organic photovoltaic cell, and that the stored charge can be used to power an electrochromic display or a bioelectronic device. Furthermore, the functionalized roots degrade in composting similarly to native roots. The proof-of-concept demonstrations illustrate the potential of this technology to achieve more sustainable solutions for powering low consumption devices such as bioelectronics for agriculture or IoT applications.

Ultrafast Metal-Free Microsupercapacitor Arrays Directly Store Instantaneous High-Voltage Electricity from Mechanical Energy Harvesters

Harvesting renewable mechanical energy is envisioned as a promising and sustainable way for power generation. Many recent mechanical energy harvesters are able to produce instantaneous (pulsed) electricity with a high peak voltage of over 100 V. However, directly storing such irregular high-voltage pulse electricity remains a great challenge. The use of extra power management components can boost storage efficiency but increase system complexity. Here utilizing the conducting polymer PEDOT:PSS, high-rate metal-free micro-supercapacitor (MSC) arrays are successfully fabricated for direct high-efficiency storage of high-voltage pulse electricity. Within an area of 2.4 × 3.4 cm2 on various paper substrates, large-scale MSC arrays (comprising up to 100 cells) can be printed to deliver a working voltage window of 160 V at an ultrahigh scan rate up to 30 V s-1. The ultrahigh rate capability enables the MSC arrays to quickly capture and efficiently store the high-voltage (≈150 V) pulse electricity produced by a droplet-based electricity generator at a high efficiency of 62%, significantly higher than that (<2%) of the batteries or capacitors demonstrated in the literature. Moreover, the compact and metal-free features make these MSC arrays excellent candidates for sustainable high-performance energy storage in self-charging power systems.

Recent Progress and Challenges in Paper-Based Microsupercapacitors for Flexible Electronics: A Comprehensive Review

Recent advances in paper-based microsupercapacitors (p-MSCs) have attracted significant attention due to their potential as substrates for flexible electronics. This review summarizes progress in the field of p-MSCs, discussing their challenges and prospects. It covers various aspects, including the fundamental characteristics of paper, the modification of paper with functional materials, and different methods for device fabrication. The review critically analyzes recent advancements, materials, and fabrication techniques for p-MSCs, exploring their potential applications and benefits, such as flexibility, cost-effectiveness, and sustainability. Additionally, this review highlights gaps in current research, guiding future investigations and innovations in the field. It provides an overview of the current state of p-MSCs and offers valuable insights for researchers and professionals in the field. The critical analysis and discussion presented herein offer a roadmap for the future development of p-MSCs and their potential impact on the domain of flexible electronics.

Dual Applications of Cobalt-Oxide-Grafted Carbon Quantum Dot Nanocomposite for Two Electrode Asymmetric Supercapacitors and Photocatalytic Behavior

Carbon materials, such as graphene, carbon nanotubes, and quantum-dot-doped metal oxides, are highly attractive for energy storage and environmental applications. This is due to their large surface area and efficient optical and electrochemical activity. In this particular study, a composite material of cobalt oxide and carbon quantum dots (Co3O4-CQD) was prepared using cobalt nitrate and ascorbic acid (carbon source) through a simple one-pot hydrothermal method. The properties of the composite material, including the functional groups, composition, surface area, and surface morphology, were evaluated by using various methods such as ultraviolet, Fourier transform infrared, X-ray diffraction, Raman, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller, scanning electron microscopy, and transmission electron microscopy analysis. The electrochemical performance of the Co3O4-CQD composite has been studied using a three-electrode system. The results show that at 1 A g-1, the composite delivers a higher capacitance of 1209 F g-1. The asymmetric supercapacitor (Co3O4-CQD//AC) provided 13.88 W h kg-1 energy and 684.65 W kg-1 power density with a 96% capacitance retention. The Co3O4-CQD composite also demonstrated excellent photocatalytic activity (90% in 60 min) for the degradation of methylene blue dye under UV irradiation, which is higher than that of pristine Co3O4 and CQD. This demonstrates that the Co3O4-CQD composite is a promising material for commercial energy storage and environmental applications.

Porous Structural Microfluidic Device for Biomedical Diagnosis: A Review

Microfluidics has recently received more and more attention in applications such as biomedical, chemical and medicine. With the development of microelectronics technology as well as material science in recent years, microfluidic devices have made great progress. Porous structures as a discontinuous medium in which the special flow phenomena of fluids lead to their potential and special applications in microfluidics offer a unique way to develop completely new microfluidic chips. In this article, we firstly introduce the fabrication methods for porous structures of different materials. Then, the physical effects of microfluid flow in porous media and their related physical models are discussed. Finally, the state-of-the-art porous microfluidic chips and their applications in biomedicine are summarized, and we present the current problems and future directions in this field.