| 1. |
- Isacsson, Patrik, 1991-
(författare)
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Materials Design for Paper Electrodes : A Papermaking Perspective on Electrode Fabrication
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The electrification and digitalization of our society has propelled the demand for energy storage solutions. High-end technologies have been developed to satisfy the requirements of demanding applications, such as electromobility and portable consumer electronics, which also increasingly find markets for less demanding applications. These markets include grid and domestic energy storage, as well as Internet of Things (IoT). However, using high-end technologies for low-end applications is a waste of resources that puts unnecessary stress on the supply lines. Thus, more low-cost cost and environmentally friendly alternative technologies are sought, among which renewable biobased materials derived from agriculture and forestry play a prominent role.The dominant chemical constituents in plants, cellulose and lignin, exhibit some intriguing electrochemical and colloidal properties. Cellulose has been found to efficiently stabilize various electronic materials, whereas lignin can be used as an electronic material itself. Lignocellulosic materials also open for papermaking as an alternative manufacturing approach. Taking the step to using papermaking methods is, however, a bit far from the technology readiness level, as the vast majority of the research on paper electrodes is based on nanocellulose. The material properties of such nanopapers are indeed extraordinary, but the lack of large-scale production methods for nanopapers is a serious challenge.To circumvent this obstacle and find a shortcut to the realization of paper electrodes, this thesis has turned to conventional papermaking techniques. Fibres are essentially different to nanofibrils by their difference in size, and the papermaking process requires careful composition of the formulations. Thus, as the research on nanopaper electrodes cannot be directly translated into conventional papermaking techniques, this calls for separate studies on fibre-based systems.This thesis is based on four separate works carried out by an explorative approach, where different kinds of paper electrodes have been investigated with touchdowns in example applications. Based on these studies, general knowledge has been concluded. This has been summarized by four important aspects for materials design of paper electrodes:Colloidal Systems. The paper electrode formulations exhibit both familiar and unfamiliar colloidal interactions. Established wet-end chemistry including charge balance control and electrostatic interactions remain important in parallel with unconventional behaviours. Exfoliated graphite forms water-stable coatings around pulp fibres and exhibit auto-retention mechanism(s). The conducting polymer system PEDOT:PSS, which can adsorb to chemical pulp fibres, does not exhibit affinity to chemi-thermomechanical pulp.Percolating Networks. Cellulosic fibres constitute an insulative matrix, in which efficient percolating conductive networks must be formed. The way a conducting additive is introduced, as well as the morphology of the additive, is important. Combining conducting polymers with nanocarbons is a promising concept for material-efficient networks. For a filler used as an electrode active material, it is important to acknowledge whether it is electronically conductive or not. A higher amount of conductive additives is required for insulative electrode active materials than for those with internal conductivity.Lignin Electrochemistry. Residual lignin present in softwood pulps, in both mechanical and chemical pulps, is electrochemically active. This can either be wanted or unwanted depending on application. Fines differ from fibres in terms of electrochemical stability and oxidative activity. Substantial competing electrochemical reactions occur, which might be related to the electrochemical stability.Mechanical Properties. Percolating conductive networks require high interconnectivity, which entails a cross-linked structure. This brings increased stiffness to the papers, which can be observed both for exfoliated graphite as a filler as well as for papers impregnated with PEDOT:PSS.Based on the four aspects described above, prospects for a few paper electrode applications have been reviewed. The prospects are mixed, each with their own challenges and opportunities which requires further research and development. While this thesis can conclude that we have not yet reached the point where paper electrodes can be realized, it certainly paves the way to get there.
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| 2. |
- Mohammadi, Mohsen, 1992-
(författare)
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Stretchable electronics using wood-based functional materials
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stretchable electronics allows for direct integration into deforming systems like clothing, skin, and tissue, thereby enabling novel applications in soft robotics, wearable electronics, health monitoring, therapeutics, and human-machine interfaces. However, achieving seamless integration with the human body poses significant challenges, necessitating the development of functional materials with a low Young’s modulus matching biological tissues to avoid any discomfort or immune response. Additionally, as electronic devices are becoming increasingly used in different settings, accumulation of electronic waste, and the utilization of unsustainable raw materials are emerging as pressing environmental challenges. Therefore, it is important that the design and fabrication of these devices consider not only high performance, but also its environmental sustainability. Therefore the focus of this thesis is on enhancing the performance and sustainability aspects of stretchable electronics through using renewable wood-based functional wood-based materials in 4 papers. Paper I focuses on the development of versatile soft electromagnetic actuators for soft robotic applications. These stretchable electromagnetic actuators were capable of contraction, expansion, hopping, and locomotion without the need for external magnetic fields. By embedding strain sensors made of conductive cellulose nanofibril (CNF)-based foam, the actuators could internally monitor their states, enhancing their controllability and autonomy. In Paper II, a soft haptic system was designed to stimulate the sense of touch. The haptic system was based on a soft electromagnetic actuator concept that included a soft magnet and stretchable conducting composite consisting of silver flakes and a styrene elastomer. The system demonstrated an improved tactile response enabled by vibration amplitude sensing through conductive CNF-based foams. This novel design offers potential applications in human–machine interfaces and virtual reality tools. Paper III presents a scalable approach for the fabrication of ultra-soft high-resolution multilayer stretchable printed circuit boards (sPCBs). A wood derived biopolymer, lignin, was used to develop a water processable sacrificial mask bio-composite for laser-patterning of high-resolution prints of ultra-soft and stretchable conductors with high-aspect-ratio structures. Additionally, this method enabled the stable integration of rigid components onto the sPCBs that can facilitate their use for miniaturized electronic devices. Lastly, paper IV introduces a fluid-based electrode concept for stretchable batteries using the biopolymer lignin. Fluidity is engineered into the cathode and anode, thereby decoupling the mechanical and electrochemical properties of the battery electrodes, allowing for high deformability without sacrificing capacity. The developed wood-based fluid stretchable battery could potentially be used as a sustainable energy storage component to power wearable devices. Overall, the thesis has contributed to the advancement of the field of stretchable electronics. It provided valuable insights into the potential utilization of wood-based functional materials into a variety of devices, fabrication methods, and design concepts in stretchable electronics, incorporating both high performance and environmental sustainability. The knowledge generated from this thesis can be used as a prospective guideline to design next-generation stretchable electronics devices.
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| 3. |
- Routier, Cyril, 1996-
(författare)
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Plant Nanobionics : From Localized Carbon Capture to Precision Molecular Delivery
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Photosynthesis is an evolutionary marvel that not only sustains plant life but also profoundly shaped the climatic conditions necessary for the development of other advanced forms of life and the ecosystems we know today. During photosynthesis, plants harness the energy of light to convert carbon dioxide (CO2), one of the main greenhouse gases, into sugars for the growth of both themselves and organisms that consume plants, and oxygen that sustains life on Earth. As we face the challenges of a rapidly changing climate and growing global population, understanding and enhancing the functions of plants such as photosynthesis and drought tolerance is of major importance.With advances in materials science over the years, an increasing number of nanotechnologies harnessing the unique properties of materials with sizes in the nanometer range (<100 nm) are emerging, holding promise to revolutionize various sectors, including agriculture and plant biology. At the intersection of materials science and plant biology, the field of plant nanobionics emerges as a transformative discipline pioneering a novel approach to integrating nanomaterials directly into plant systems. Departing from traditional genetic modification, this interdisciplinary field seeks to create bio-hybrid systems to enhance plants’ natural functions such as photosynthesis or introduce entirely new capabilities such as environmental sensing, monitoring, or even light emission.Various strategies exist in plant nanobionics, including the use of carbon nanotubes, silica nanoparticles, liposomes, or even quantum dots. The use of polymers, which consist of long chains of molecules with repeating units, has also been particularly intriguing for nanotechnological and nanobionic approaches due to their versatile and tunable properties.The primary focus of this thesis was to increase the diffusion rate of atmospheric CO2 in the leaves of tobacco plants using polymeric nanoparticles. The nanoparticles are engineered to directly capture CO2 from the atmosphere and are able to cross various plant cell membranes to deliver it to the photosynthetic reaction centers. The initial carboxylation reaction of photosynthesis, where atmospheric CO2 is converted into sugar precursors (3-phosphoglyceric acid or 3-PGA) with the help of the enzyme RuBisCO, is often considered the limiting step of the photosynthetic process. The poor affinity of RuBisCO to CO2 coupled with the limited diffusion of CO2 to the reaction sites is responsible for a considerable reduction in the potential photosynthetic efficiency of plants.With that in mind, we designed nanoparticles based on polyethyleneimine, a polymer able to capture atmospheric CO2 and cross cellular membranes, and modified it with chitosan, a biocompatible polymer, to design nanoparticles that we further labeled with fluorescein isothiocyanate (FITC) for fluorescent observation purposes. We studied their ability to self-integrate into plant cells and the plant chloroplasts, where the photosynthetic reaction occurs, without causing harm to the cells or the plants in general. We further evaluated the capacity of the nanoparticles to integrate into plant cells in culture and demonstrated that the nanoparticles have a natural affinity for the cells and self-integrate in the cells, crossing the cell wall, after 3 days. The nanoparticles also had no negative impact on the capacity of the cells to keep growing and dividing. We also demonstrated the nanoparticles' ability to still capture atmospheric CO2 when integrated into plant leaves and, in vitro, to redistribute it to RuBisCO enhancing the production of 3-PGA by 20%. Since the entry of the nanoparticles into plant leaves requires forced infiltration using a syringe infiltration method, we also studied the impact of the method itself on the plants' natural capacity to uptake CO2 and perform photosynthesis. We found there was a temporary impact of the infiltration process on the leaves’ natural CO2 uptake that also resulted in a reduction of their natural photosynthetic abilities. This will enable future studies to reliably quantify the impact of the nanoparticles on plant processes. We also used an organic electronic ion pump as a precision delivery method to study the impact of various biomolecules, such as malic and abscisic acid, on the plants' natural regulation of carbon dioxide uptake through the leaf pores known as stomata.Our work elucidates the various mechanisms at play when infiltrating nanoparticles or delivering biomolecules into plant leaves and plant cells in culture. We demonstrated a proof-of-concept use of phytocompatible nanoparticles in vivo, paving the way for a nanomaterials-based CO2-concentrating mechanism in plants that can potentially increase plants’ photosynthetic efficiency and overall CO2 storage.
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| 4. |
- Zabihipour, Marzieh, 1985-
(författare)
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Organic Electrochemical Transistors for Printed Digital Circuits
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organic electronics enables cost-effective production of flexible electronic devices with high throughput and easy processing compared to the conventional electronics. Organic electronics, therefore, has the potential to realize various innovative applications on a large scale, for example, flexible displays, smart windows, solar cells, electronic skin and implantable medical devices.Many of the materials employed in the field of organic electronics can be processed from chemical solutions. This allows for making various types of inks and hence the possibility to use the traditional high-volume printing methods such as screen printing, inkjet printing and gravure printing for fabricating organic electronic devices on different surfaces. Screen printing has advantages over the other methods in terms of the range of ink viscosity, resolution, and controllable thickness of dry ink film.For various applications envisioned for an integration of printed organic electronics with other technology platforms, a prolonged lifetime and low power consumption are desired. This requires an optimized design of the electronic components and circuits so that they can operate at reduced voltages to guarantee both the long lifetime and the low power consumption. This thesis focuses on designing fully screen printed vertically stacked organic electrochemical transistors (OECTs) and OECT-based circuits operating at low supply voltages and at the same time delivering high gain and low power consumption with long lifetime. The OECTs and OECT-based circuits employ poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) as the organic polymer in their channel. The multi-layered OECTs have a small footprint with a high manufacturing yield and performance uniformity across the printed area, making them suitable for complex printed circuits. Furthermore, various inverter designs based on the reliable and reproducible OECTs are developed and explored to target circuits that can perform at relatively low supply voltages, yet offering improved performance.
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| 5. |
- Gryszel, Maciej, et al.
(författare)
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Vertical Organic Electrochemical Transistor Platforms for Efficient Electropolymerization of Thiophene Based Oligomers
- 2024
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534.
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Tidskriftsartikel (refereegranskat)abstract
- Organic electrochemical transistors (OECTs) have emerged as promising candidates for various fields, including bioelectronics, neuromorphic computing, biosensors, and wearable electronics. OECTs operate in aqueous solutions, exhibit high amplification properties, and offer ion-to-electron signal transduction. The OECT channel consists of a conducting polymer, with PEDOT:PSS receiving the most attention to date. While PEDOT:PSS is highly conductive, and benefits from optimized protocols using secondary dopants and detergents, new p-type and n-type polymers are emerging with desirable material properties. Among these, low-oxidation potential oligomers are highly enabling for bioelectronics applications, however the polymers resulting from their polymerization lag far behind in conductivity compared with the established PEDOT:PSS. In this work we show that by careful design of the OECT geometrical characteristics, we can overcome this limitation and achieve devices that are on-par with transistors employing PEDOT:PSS. We demonstrate that the vertical architecture allows for facile electropolymerization of a family of trimers that are polymerized in very low oxidation potentials, without the need for harsh chemicals or secondary dopants. Vertical and planar OECTs are compared using various characterization methods. We show that vOECTs are superior platforms in general and propose that the vertical architecture can be expanded for the realization of OECTs for various applications.
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