Selective deposition of metal oxide nanoflakes on graphene electrodes to obtain high-performance asymmetric micro-supercapacitors

To meet the charging market demands of portable microelectronics, there has been a growing interest in high performance and low-cost microscale energy storage devices with excellent flexibility and cycling durability. Herein, interdigitated all-solid-state flexible asymmetric micro-supercapacitors (A-MSCs) were fabricated by a facile pulse current deposition (PCD) approach. Mesoporous Fe2O3 and MnO2 nanoflakes were functionally coated by electrodeposition on inkjet-printed graphene patterns as negative and positive electrodes, respectively. Our PCD approach shows significantly improved adhesion of nanostructured metal oxide with crack-free and homogeneous features, as compared with other reported electrodeposition approaches. The as-fabricated Fe2O3/MnO2 A-MSCs deliver a high volumetric capacitance of 110.6 F cm(-3) at 5 mu A cm(-2) with a broad operation potential range of 1.6 V in neutral LiCl/PVA solid electrolyte. Furthermore, our A-MSC devices show a long cycle life with a high capacitance retention of 95.7% after 10 000 cycles at 100 mu A cm(-2). Considering its low cost and potential scalability to industrial levels, our PCD technique could be an efficient approach for the fabrication of high-performance MSC devices in the future

Inkjet Printing of Graphene-based Microsupercapacitors for Miniaturized Energy Storage Applications

Printing technologies are becoming increasingly popular because they enable the large-scale and low-cost production of functional devices with various designs, functions, mechanical properties and materials. Among these technologies, inkjet printing is promising thanks to its direct (mask-free) patterning, non-contact nature, low material waste, resolution down to 10 µm, and compatibility with a broad range of materials and substrates. As a result, inkjet printing has applications in several fields like wearables, opto-electronics, thin-film transistors, displays, photovoltaic devices, and in energy storage. It's in energy storage that the technique shows its full potential by allowing the production of miniaturized devices with a compact form factor, high power density and long cycle life, called microsupercapacitors (MSCs). To this end, graphene has a number of remarkable properties like high electrical conductivity, large surface area, elasticity and transparency, making it a top candidate as an electrode material for MSCs. Some key drawbacks limit the use of inkjet printing for the production of graphene-based MSCs. This thesis aims at improving its scalability by producing fully inkjet printed devices, and extending its applications through the integration of inkjet printing with other fabrication techniques. MSCs typically rely on the deposition by hand of gel electrolyte that is not printable or by submerging the whole structure into liquid electrolyte. Because of this, so far large-scale production of more than 10 interconnected devices has not been attempted. In this thesis, a printable gel electrolyte ink based on poly(4-styrene sulfonic acid) was developed, allowing the production of large arrays of more than 100 fully inkjet printed devices connected in series and parallel that can be reliably charged up to 12 V. Also, a second electrolyte ink based on nano-graphene oxide, a solid-state material with high ionic conductivity, was formulated to optimize the volumetric performance of these devices. The resulting MSCs were also fully inkjet printed and exhibited an overall device thickness of around 1 µm, yielding a power density of 80 mW cm-3. Next, the use of inkjet printing of graphene was explored for the fabrication of transparent MSCs. This application is typically hindered by the so-called coffee-ring effect, which creates dark deposits on the edges of the drying patterns and depletes material from the inside area. In light of this issue, inkjet printing was combined with etching to remove the dark deposits thus leaving uniform and thin films of graphene with vertical sidewalls. The resulting devices showed a transmittance of up to 90%. Finally, the issue of the substrate compatibility of inkjet printed graphene was addressed. Although inkjet printing is considered to have broad substrate versatility, it is unreliable on hydrophilic or porous substrates and most inks (including graphene inks) require thermal annealing that damages substrates that are not resistant to heat. Accordingly, a technique based on inkjet printing and wet transfer was developed to reliably deposit graphene-based MSCs on a number of substrates, including flat, 3D, porous, plastics and biological (plants and fruits) with adverse surfaces. The contributions of this thesis have the potential to boost the use of inkjet printed MSCs in applications requiring scalability and resolution (e.g. on-chip integration) as well as applications requiring conformability and versatility (e.g. wearable electronics).QC 20190816</p

Inkjet Printing of Graphene-based Microsupercapacitors for Miniaturized Energy Storage Applications

Printing technologies are becoming increasingly popular because they enable the large-scale and low-cost production of functional devices with various designs, functions, mechanical properties and materials. Among these technologies, inkjet printing is promising thanks to its direct (mask-free) patterning, non-contact nature, low material waste, resolution down to 10 µm, and compatibility with a broad range of materials and substrates. As a result, inkjet printing has applications in several fields like wearables, opto-electronics, thin-film transistors, displays, photovoltaic devices, and in energy storage. It's in energy storage that the technique shows its full potential by allowing the production of miniaturized devices with a compact form factor, high power density and long cycle life, called microsupercapacitors (MSCs). To this end, graphene has a number of remarkable properties like high electrical conductivity, large surface area, elasticity and transparency, making it a top candidate as an electrode material for MSCs. Some key drawbacks limit the use of inkjet printing for the production of graphene-based MSCs. This thesis aims at improving its scalability by producing fully inkjet printed devices, and extending its applications through the integration of inkjet printing with other fabrication techniques. MSCs typically rely on the deposition by hand of gel electrolyte that is not printable or by submerging the whole structure into liquid electrolyte. Because of this, so far large-scale production of more than 10 interconnected devices has not been attempted. In this thesis, a printable gel electrolyte ink based on poly(4-styrene sulfonic acid) was developed, allowing the production of large arrays of more than 100 fully inkjet printed devices connected in series and parallel that can be reliably charged up to 12 V. Also, a second electrolyte ink based on nano-graphene oxide, a solid-state material with high ionic conductivity, was formulated to optimize the volumetric performance of these devices. The resulting MSCs were also fully inkjet printed and exhibited an overall device thickness of around 1 µm, yielding a power density of 80 mW cm-3. Next, the use of inkjet printing of graphene was explored for the fabrication of transparent MSCs. This application is typically hindered by the so-called coffee-ring effect, which creates dark deposits on the edges of the drying patterns and depletes material from the inside area. In light of this issue, inkjet printing was combined with etching to remove the dark deposits thus leaving uniform and thin films of graphene with vertical sidewalls. The resulting devices showed a transmittance of up to 90%. Finally, the issue of the substrate compatibility of inkjet printed graphene was addressed. Although inkjet printing is considered to have broad substrate versatility, it is unreliable on hydrophilic or porous substrates and most inks (including graphene inks) require thermal annealing that damages substrates that are not resistant to heat. Accordingly, a technique based on inkjet printing and wet transfer was developed to reliably deposit graphene-based MSCs on a number of substrates, including flat, 3D, porous, plastics and biological (plants and fruits) with adverse surfaces. The contributions of this thesis have the potential to boost the use of inkjet printed MSCs in applications requiring scalability and resolution (e.g. on-chip integration) as well as applications requiring conformability and versatility (e.g. wearable electronics).QC 20190816</p

Inkjet Printing of Graphene-based Microsupercapacitors for Miniaturized Energy Storage Applications

Printing technologies are becoming increasingly popular because they enable the large-scale and low-cost production of functional devices with various designs, functions, mechanical properties and materials. Among these technologies, inkjet printing is promising thanks to its direct (mask-free) patterning, non-contact nature, low material waste, resolution down to 10 µm, and compatibility with a broad range of materials and substrates. As a result, inkjet printing has applications in several fields like wearables, opto-electronics, thin-film transistors, displays, photovoltaic devices, and in energy storage. It's in energy storage that the technique shows its full potential by allowing the production of miniaturized devices with a compact form factor, high power density and long cycle life, called microsupercapacitors (MSCs). To this end, graphene has a number of remarkable properties like high electrical conductivity, large surface area, elasticity and transparency, making it a top candidate as an electrode material for MSCs. Some key drawbacks limit the use of inkjet printing for the production of graphene-based MSCs. This thesis aims at improving its scalability by producing fully inkjet printed devices, and extending its applications through the integration of inkjet printing with other fabrication techniques. MSCs typically rely on the deposition by hand of gel electrolyte that is not printable or by submerging the whole structure into liquid electrolyte. Because of this, so far large-scale production of more than 10 interconnected devices has not been attempted. In this thesis, a printable gel electrolyte ink based on poly(4-styrene sulfonic acid) was developed, allowing the production of large arrays of more than 100 fully inkjet printed devices connected in series and parallel that can be reliably charged up to 12 V. Also, a second electrolyte ink based on nano-graphene oxide, a solid-state material with high ionic conductivity, was formulated to optimize the volumetric performance of these devices. The resulting MSCs were also fully inkjet printed and exhibited an overall device thickness of around 1 µm, yielding a power density of 80 mW cm-3. Next, the use of inkjet printing of graphene was explored for the fabrication of transparent MSCs. This application is typically hindered by the so-called coffee-ring effect, which creates dark deposits on the edges of the drying patterns and depletes material from the inside area. In light of this issue, inkjet printing was combined with etching to remove the dark deposits thus leaving uniform and thin films of graphene with vertical sidewalls. The resulting devices showed a transmittance of up to 90%. Finally, the issue of the substrate compatibility of inkjet printed graphene was addressed. Although inkjet printing is considered to have broad substrate versatility, it is unreliable on hydrophilic or porous substrates and most inks (including graphene inks) require thermal annealing that damages substrates that are not resistant to heat. Accordingly, a technique based on inkjet printing and wet transfer was developed to reliably deposit graphene-based MSCs on a number of substrates, including flat, 3D, porous, plastics and biological (plants and fruits) with adverse surfaces. The contributions of this thesis have the potential to boost the use of inkjet printed MSCs in applications requiring scalability and resolution (e.g. on-chip integration) as well as applications requiring conformability and versatility (e.g. wearable electronics).QC 20190816</p

Hexosomes as Drug Delivery Vehicles for Antimicrobial Peptides

This master thesis project was carried out at SP Technical Research Institute of Sweden within the FORMAMP project which goal is to increase the efficiency and stability of antimicrobial peptides (AMPs) by exploring and developing a number of innovative formulation strategies for the drug delivery of those systems. In view of the growing problem of bacterial resistance to traditional antibiotics, AMPs represent one of the most promising alternatives as therapeutics against infectious diseases: besides having a fast and non-specific mechanism of action, they are less prone to bacterial resistance. In this project, the goal was to develop an efficient method for the formulation of hexagonal lyotropic phase nanodispersions (called hexosomes) as drug delivery vehicles for the AP114, DPK-060 and LL-37 AMPs. Then, these formulations were characterized through size measurements, zeta potential measurements, SAXS, cryo-TEM and UPLC and their stability was assessed. Lastly, the interaction of these systems with model bacterial membranes was tested through QCM-D and ellipsometry. The relevant samples were found to have a hexagonal structure with the lattice parameter being larger when peptide was loaded. The systems were observed to be sufficiently stable and the peptide loading efficiency was found to be higher than 90% in most cases. The hexosomes loaded with LL-37 were observed to preserve the effectiveness of the peptide when interacting with the model membrane through QCM-D

Drying-Mediated Self-Assembly of Graphene for Inkjet Printing of High-Rate Micro-supercapacitors

Scalable fabrication of high-rate micro-supercapacitors (MSCs) is highly desired for on-chip integration of energy storage components. By virtue of the special self-assembly behavior of 2D materials during drying thin films of their liquid dispersion, a new inkjet printing technique of passivated graphene micro-flakes is developed to directly print MSCs with 3D networked porous microstructure. The presence of macroscale through-thickness pores provides fast ion transport pathways and improves the rate capability of the devices even with solid-state electrolytes. During multiple-pass printing, the porous microstructure effectively absorbs the successively printed inks, allowing full printing of 3D structured MSCs comprising multiple vertically stacked cycles of current collectors, electrodes, and sold-state electrolytes. The all-solid-state heterogeneous 3D MSCs exhibit excellent vertical scalability and high areal energy density and power density, evidently outperforming the MSCs fabricated through general printing techniques.publishedVersionPeer reviewe

Facile fabrication of graphene-based highperformance microsupercapacitors operating ata high temperature of 150C

Many industry applications require electronic circuits and systems to operate at high temperatures over 150 °C. Although planar microsupercapacitors (MSCs) have great potential for miniaturized on-chip integrated energy storage components, most of the present devices can only operate at low temperatures (&lt;100 °C). In this work, we have demonstrated a facile process to fabricate activated graphene-based MSCs that can work at temperatures as high as 150 °C with high areal capacitance over 10 mF cm−2 and good cycling performance. Remarkably, the devices exhibit no capacitance degradation during temperature cycling between 25 °C and 150 °C, thanks to the thermal stability of the active components

Scalable Fabrication and Integration of Graphene Microsupercapacitors through Full Inkjet Printing

A simple full-inkjet-printing technique is developed for the scalable fabrication of graphene-based microsupercapacitors (MSCs) on various substrates. High-performance graphene inks are formulated by integrating the electrochemically exfoliated graphene with a solvent exchange technique to reliably print graphene interdigitated electrodes with tunable geometry and thickness. Along with the printed polyelectrolyte, poly­(4-styrenesulfonic acid), the fully printed graphene-based MSCs attain the highest areal capacitance of ∼0.7 mF/cm², substantially advancing the state-of-art of all-solid-state MSCs with printed graphene electrodes. The full printing solution enables scalable fabrication of MSCs and effective connection of them in parallel and/or in series at various scales. Remarkably, more than 100 devices have been connected to form large-scale MSC arrays as power banks on both silicon wafers and Kapton. Without any extra protection or encapsulation, the MSC arrays can be reliably charged up to 12 V and retain the performance even 8 months after fabrication