Archive for the ‘Community Board’ Category

Photo-induced synthesis of polymeric nanoparticles and chemiluminescent degradable materials via flow chemistry

Polymeric particles represent a widely utilized class of materials due to their adjustable size and shape, high volume-surface area ratio, customizable properties and ease of surface modification. These attributes make them indispensable across diverse fields, finding applications in coatings, pigments, drug delivery, nanomedicine, catalysis and more. Traditional methods of synthesis, predominantly via thermal heterogeneous polymerization like emulsion or dispersion polymerization, often necessitate the use of surfactants/stabilizers and thermal initiators, risking material contamination and complicating purification processes. In recent years, light polymerization has gained significant attention due to its ability to operate under milder conditions and offer temporal regulation. However, employing the photo-flow reaction, which is commonly viewed as an appealing method for upscaling reactions, proves challenging for heterogeneous systems due to constraints such as limited light penetration and scattering.

In a recent study by Holloway et al., an upscaled, photochemical synthesis of polymeric particles via flow chemistry was achieved based on precipitation step-growth polymerization without radical or surfactant sources. This innovative approach optimized an easy, scalable, and fast synthetic procedure and produced functional polymeric materials with chemiluminescent self-reporting properties and chemical-stimulated degradability, thus opening novel avenues for scaled-up synthesis of functional polymeric particles (Figure 1).

Figure 1: (A) Overview of the particle formation with AA and BB2 monomers and subsequent cleavage of the oxalate bond in presence of H2O2, resulting in the degradation of the particles and light emission. (B) SEM image of the particles after synthesis. (C) SEM image of the particles after adding H2O2. (D) Photocount recorded at various particles concentrations. Reproduced from DOI: 10.1039/D4MH00106K with permission from the Royal Society of Chemistry.

Harnessing their expertise in photochemical reactions, the team synthesized functional AA and BB monomers capable of Diels-Alder step-growth polymerization under light irradiation. The oligomers, with limited solubility in the reaction solvent, precipitated out upon reaching a critical molecular weight, facilitating particle formation via precipitation polymerization mechanism. Thorough optimization of polymerization parameters enabled precise control over particle size, yield, and shape, with solvent selection and flow rate playing crucial roles in the process. The solvent selection significantly affected polymer solubility, with dramatic effects on yield and particle size. The reaction yield increased impressively, from 1% in acetonitrile, a commonly used solvent, to up to 60% in the optimized water/methanol mixture. Since the reactions took place in a flow system, the flow rate was of paramount importance. In-depth investigation revealed that tuning the flow rate allowed manipulation of reaction yield, particle size, and shape, with the ability to tune the particle size over 545 nm (ranging from 185 to 730 nm). Furthermore, the initial monomer concentration played an important role in the reaction, as the limited solubility of the monomers prohibited equimolar monomer ratios at higher concentrations, significantly affecting particle morphology.

After successfully demonstrating the photo-flow reaction, the authors took advantage of the polymer’s nature, demonstrating its potential application in point-of-care devices. The Diels-Alder adduct exhibited intrinsic fluorescence, serving as a fluorophore for the peroxylate chemiluminescent reaction. Specifically, upon the addition of H2O2, the particles degraded via oxalate bond cleavage, resulting in the excitation of the fluorophore and subsequent photon emission with a strong signal, allowing for degradation monitoring.

In summary, this work surpasses previous approaches by developing a scalable photo-flow system capable of producing polymeric particles with tuneable properties within minutes, free from additives or radical initiators. The molecular design of these polymers enables the synthesis of functional and degradable particles responsive to chemical stimuli, featuring the potential for diverse applications. Overall, this study elegantly combines fundamental aspects of polymerization and materials design to pave the way for a plethora of applications in various fields.

To find out more, please read:

Photo-induced synthesis of polymeric nanoparticles and chemiluminescent degradable materials via flow chemistry
Joshua O. Holloway, Laura Delafresnaye, Emily M. Cameron, Jochen A. Kammerer and Christopher Barner-Kowollik
Mater. Horiz., 2024, DOI:10.1039/D4MH00106K

 


About the blogger


 

Dr. Kostas Parkatzidis is a Swiss National Science Foundation Postdoc Fellow in the group of Professor Zhenan Bao at Stanford University (United States), working on the molecular design of polymer-based skin-inspired materials for various applications. Kostas obtained his PhD from ETH Zurich (Switzerland) under the supervision of Professor Athina Anastasaki where he focused on the development of advanced polymer synthesis and chemical recycling methodologies. He also holds MSc in Organic Chemistry and BSc in Materials Science and Technology obtained from the University of Crete (Greece). Since 2023, Kostas has served as a Materials Horizons Community Board member.

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Development of High-Toughness Liquid-Free Ionic Conductive Elastomers Through Multiple Cross-Linking Strategies

Current ionic conductors, such as hydrogels and ionogels, offer diverse capabilities but also exhibit limitations. These systems rely on a substantial amount of liquid to provide a mobile environment for free ions, while a covalently crosslinked network enhances mechanical strength. However, the presence of liquid compromises thermal and electrochemical stability and reduces mechanical integrity. Furthermore, the covalently crosslinked network often results in irreversible polymer structures, creating a fundamental conflict between ionic conductivity, self-healing capabilities, and mechanical performance—challenges that are particularly pronounced in flexible and wearable ionotronic devices. To address these issues, many researchers are focusing on developing versatile ionic conductive elastomers with innovative polymer molecular structures. Yet, the design of liquid-free ion-conducting elastomers typically struggles to achieve high ionic conductivity due to restricted segmental motion of polymer chains in covalently crosslinked networks, leading to significantly slower ion transport efficiency and a reduced volume of free ions.

Figure 1: Molecular structure and mechanism design of SSxDAy–LiTFSIz%. (a) Schematic of the molecular structure of a high-strength, ultra-toughness and healing polyurethane with multiple dynamic bonding interactions in this elastomer. (b) SSxDAy–LiTFSIz%-based (i) wearable strain and (ii) pressure sensors and (iii) self-powered TENG. Reproduced from DOI: 10.1039/d3mh02217j with permission from the Royal Society of Chemistry.

To enhance molecular segmental motion and ion transport, Ou and colleagues recently proposed a strategy that combines dual dynamic covalent bonds with non-covalent interactions. By integrating multilevel hydrogen bonds, disulfide bonds, and dynamic donor-acceptor (D–A) bonds into a polyurethane system, they developed liquid-free ionic conductive polyurethane elastomers (ICPEs), designated as SS50DA50–LiTFSIz%. Polytetramethylene ether glycol was selected as the soft phase, whereas the ether chain segments engage in ionic transport through loosely coordinated lithium-oxygen (O–Li+) bonding interactions. This configuration facilitates the development of all-solid ICPEs characterized by high ionic conductivity. The well-designed structure of SS50DA50 enables self-healing at 130°C for 2 hours, achieving a high tensile strength of 58.90 MPa and toughness of 260.33 MJ m-3, with a healing efficiency of 92% and complete recyclability. This performance is attributed to the dynamic covalent crosslinked bonds that maintain the relative positions of the polymer chain segments under tension, thereby maintaining the three-dimensional integrity of the network and substantially improving both the tensile strength and toughness of the elastomers. Additionally, the ICPEs (SS50DA50–LiTFSI80%) demonstrated high mechanical strength (1.18 MPa), superior ionic conductivity (0.14 mS cm-1), and excellent healing capacity (healing efficiency >95%), highlighting their potential as wearable sensors for physical rehabilitation training.

Because of their excellent sensitivity and durability properties, the SS50DA50–LiTFSI80% elastomers are used in multifunctional sensors and triboelectric nanogenerators, capable of real-time and rapid detection of various human activities, and can recognize writing signals and encrypted information transmission. Furthermore, SS50DA50–LiTFSI80% achieved an excellent open-circuit voltage of 464 V, a short-circuit current of 16 mA, a transferred charge of 50 nC, and a power density of 720 mW m-2. Its outstanding output performance offers significant practical value for wearable electronics and self-powered products.

In summary, the innovative design of ICEs such as SS50DA50–LiTFSI80% features a polyurethane matrix enriched with multiple dynamic bonds, including hydrogen and disulfide bonds. This design offers a more robust and sustainable alternative with enhanced functionality compared to traditional hydrogels. The improved mechanical properties, healing abilities, and recyclability of these materials make them pivotal for the future of flexible and wearable technology. The potential applications of these elastomers extend from sustainable wearable electronics to energy-harvesting devices and solid-state polymer electrolytes.

To find out more, please read:

Liquid-free ionic conductive elastomers with high mechanical properties and ionic conductivity for multifunctional sensors and triboelectric nanogenerators
Fangyan Ou, Ting Xie, Xinze Li, Zhichao Zhang, Chuang Ning, Liang Tuo, Wenyu Pan, Changsheng Wang, Xueying Duan, Qihua Liang, Wei Gao, Zequan Li,* and Shuangliang Zhao
Mater. Horiz., 2024, DOI: 10.1039/d3mh02217j

 


About the blogger


 

Fang Cheng Liang is currently a Lecturer in the Department of Materials Science and Engineering at the National University of Singapore (NUS) and serves as a Community Board member for Materials Horizons. Before joining NUS, he was a Research Assistant Professor at the Research and Development Center for Smart Textile Technology at the National Taipei University of Technology, Taiwan. He earned dual Ph.D. degrees in Organic Chemistry and Polymer Science and Engineering from the University Grenoble Alpes and National Taipei University of Technology in 2019. His research focuses on sustainable self-healing soft materials, liquid metal hydrogels, reconfigurable liquid crystal elastomers, and hybrid organic-inorganic perovskite applications in light-emitting diodes, triboelectric nanogenerators, soft robotics, and wearable electronics.

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Bioelectronic Wound Dressings for Realtime Monitoring of Patient Health

Patients with diabetes frequently develop chronic ulcers on their lower extremities that are extremely challenging to treat. To accelerate healing, numerous wound dressings have been developed to protect damaged tissue and possibly deliver therapeutics. However, few dressings can provide real-time monitoring of wound healing and patient health. Since diabetic ulcers are prone to persistent hyperglycemia, ischemia, prolonged inflammation, and bacterial infections, frequently assessing biomarkers is essential to optimize treatment and maximize healing outcomes.

In a recent work by Hou et. al., a multifunctional wound dressing is developed to not only shield diabetic foot wounds from insult and bacterial infections, but record wound site temperature, pH, and glucose levels. Additionally, the flexible electronic also monitors physiological signals such as patient heart rhythm and brain activity. To create the diagnostic dressing, a poly(ethylene glycol)-based polymer possessing cationic and anionic moieties, as well as the self-complementary hydrogen-bonding group, ureidopyrimidinone (UPy) is developed. The polymer abbreviated PADU after the first letter of each constituting monomer, forms flexible substrates due to intermolecular UPy interactions as well as ionic bonding between cationic and ionic segments.

 

Figure 1: Schematics of using the diagnostic wound dressings, the internal molecular structure and corresponding performance of flexible polymeric substrates. Reproduced from DOI: 10.1039/D3MH02064A with permission from the Royal Society of Chemistry.

 

When applied to metals, rubber, plastic, glass, and biological tissues, PADU substrates display remarkable adhesion, notably exceeding an adhesive strength of 13 kPa for both diabetic and healthy mouse skin. Following damage to the patch, dynamic hydrogen bonding also endows PADU materials with self-healing capabilities, restoring 96% of their original mechanical strength after 24 hours. In practical use this gives PADU substrates a huge advantage because may be able to sustain electronic function despite physical damage from bodily movement.

In addition to its superb mechanical properties, PADU was also found to exhibit antibacterial activity. Killing of bacteria is achieved through disruption of the cell membrane by cationic groups within the polymer, making it active against even drug-resistant pathogens. Co-cultures with mammalian cells and blood cells, however, showed no cytotoxic or hemolytic effects, and biocompatibility was further confirmed by subcutaneous implantation into mice.

When glucose, pH, and temperature sensors were printed on PADU substrates, real-time monitoring of environmental conditions were reported with high accuracy. Gold foil electrodes could also be easily integrated into the patch to produce dressings capable of collecting electrocardiograms, electromyographic signals, and electroencephalograms. Due to their strong adhesion to skin, PADU-based sensors could even collect electrophysiological readings while patients were in motion, exceeding the accuracy of commercial sensors.

The dressing developed in the work by Hou, et. al. surpasses the capabilities of most diabetic wound dressings due its multifunctional performance as an adhesive and versatile electronic. Although initially designed for diabetic ulcers, the technology will likely find broad use as a diagnostic dressing for any type of slow-healing wound. In future studies, electronic patches may even be studied as implantable materials to monitor surgical site healing or internal injuries. Overall, the work demonstrates the vast utility of flexible bioelectronics and highlights the importance of developing new devices that not only treat but monitor chronic wounds.

To find out more, please read:

Skin-adhesive and self-healing diagnostic wound dressings for diabetic wound healing recording and electrophysiological signal monitoring
Zishuo Hou, Tengjiao Wang, Lei Wang, Junjie Wang, Yong Zhang, Qian Zhou,   Zhengheng Zhang, Peng Li and Wei Huang
Mater. Horiz., 2024, Advance Article, DOI: 10.1039/D3MH02064A


About the blogger


 

Kelsey DeFrates is a Materials Horizons Community Board member. She received her Bachelor of Science in Bioengineering at Rowan University (Glassboro, New Jersey) in 2018 and completed her Ph.D. in Bioengineering through the University of California, Berkeley – UCSF joint graduate program in 2023. For her thesis research, Kelsey worked with Professor Phillip Messersmith at UC Berkeley on the development of supramolecular materials for drug delivery and tissue regeneration. In 2023, Kelsey joined Professor Christopher Hernandez at UCSF as a Chancellor’s Postdoctoral Fellow, where she is working to understand how bacteria sense and respond to physical stimuli. In future work, Kelsey hopes to use this information to develop engineered living materials for healthcare and sustainable building.

 

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Dual substitution strategy to promote ionic conductivity of solid-state electrolyte

Electrification of transportation has become one of the most important central themes of modern society to build a sustainable system. The market for electric vehicles (EVs), which are powered by Li-ion batteries (LIBs), has been growing very rapidly and continuously. While EVs have become more popular on the road, there are concerns about their safety and somewhat limited driving ranges. In this respect, solid-state Li metal batteries have been extensively explored because of the following merits. First, solid-state electrolytes are more resistant to catching fire than liquid organic electrolytes that are flammable. Second, solid-state electrolytes are expected to be more stable against lithium metal dendrite penetration, which allows the use of energy-dense lithium metal anodes instead of graphitic carbon. However, it is still challenging to achieve “practical” high-energy density of solid-state Li metal batteries, which requires thick composite cathodes enabled by super-ionic conductors (>10 mS/cm). Although we have observed significant progress in improving the ionic conductivities of solid-state electrolytes, more fundamental studies to understand important parameters promoting lithium-ion conductivity and further exploration in new chemical spaces are needed.

A recent study by Han and colleagues developed a new borohydride/halide dual-substituted argyrodite-type solid-state electrolyte, which achieves an ionic conductivity of > 26 mS/cm after low-temperature sintering. They synthesized the borohydride/halide dual-substituted argyrodite solid-state electrolytes using a two-step ball-milling method from β-Li3PS4, LiBH4, and LiCl. While they also tried to incorporate Br and I instead of Cl in the argyrodite solid-state electrolytes, they always produced unknown impurity phases and exhibited lower ionic conductivity. When they varied the compositions (2.5 ≥ x ≥ 1.5, Li3PS4 + xLiBH4 + 0.5LiCl), it was found that the composition of Li3PS4 + 2LiBH4 + 0.5LiCl (x = 2) exhibits the highest ionic conductivity of 16.4 mS/cm without sintering and 26.1 mS/cm after the sintering. They claimed that the increase of occupancy of BH4in 4a may harm the ionic conductivity when x is larger than 2, but it still remains an open question why x = 2 composition has a sweet spot for the highest ionic conductivity in their system.

Figure 1: (a) Nyquist plots of Li3PS4 + xLiBH4 + 0.5LiCl (2.5 ≥ x ≥ 1.5) and commercial Li6PS5Cl. (b) EIS spectra of Li5.35PS4.35(BH4)1.15Cl0.5 at various temperatures. (c) Arrhenius plots and the activation energy of Li3PS4 + xLiBH4 + 0.5LiCl (2.5 ≥ x ≥ 1.5) and commercial Li6PS5Cl. (d) BH4- occupancy of 4a and 4d sites for each electrolyte and its ionic conductivity. The dashed lines are the trend lines of each site. Reproduced from DOI: 10.1039/D3MH01450A with permission from the Royal Society of Chemistry.

They further investigated the electrochemical properties, including oxidation stability limit, Li metal deposition/stripping cycles, and full cell tests. While they confirmed that their borohydride/halide dual-substituted argyrodite-type solid-state electrolytes are stable up to 5.0 V (vs. Li/Li+) using cyclic voltammetry (CV) technique, they used a simple cell configuration of Li-metal/solid-state electrolyte/current collector, which often overestimates oxidation limits. In the Li/solid-state electrolyte/Li symmetric cycling tests, they achieved stable cycling for up to 2000 hours (at 1mA/cm2, for 1 hour charge – 1 hour discharge cycles) and high critical current density (CCD) of 2.5 mA/cm2. They also confirmed the practical feasibility of their solid-state electrolytes in full-cell tests where Li metal and LiNbO3-coated LiNi0.8Co0.1Mn0.1O2 are used as an anode and a cathode, respectively.

In conclusion, Han et al. demonstrated that the dual substitution of borohydride and halide enhances lithium-ionic conductivity of argyrodite-type solid-state electrolytes significantly. Their work sheds light on a new strategy of dual substitution to achieve super-ionic conductivity although there are remaining important questions to understand (i) why only Cl could be soluble in the argyrodite structure along with borohydride and (ii) why a specific composition shows the best ionic conductivity. Answering the questions above will give us better insights to design even better super-ionic conductors in the future.

To find out more, please read:

Borohydride and halide dual-substituted lithium argyrodites
Ji-Hoon Han, Do Kyung Kim, Young Joo Lee, Young-Su Lee, Kyung-Woo Yi and  Young Whan Cho.
Mater. Horiz., 2024, 11, 251-261, DOI: 10.1039/D3MH01450A


About the blogger


Haegyeom Kim is a Staff Scientist at Materials Sciences Division of Lawrence Berkeley National Laboratory (LBNL) and a Community Board member of Materials Horizons. In 2016-2019, he worked as a postdoctoral researcher at the LBNL (Supervisor: Prof. Gerbrand Ceder). He also spent 1 year as a postdoctoral researcher at Research Institute of Advanced Materials in Seoul National University (SNU) (Supervisor: Prof. Kisuk Kang) in 2015-2016. Dr. Kim completed his PhD degree in Materials Science and Engineering from SNU in 2015 (Advisor: Prof. Kisuk Kang), Master’s Degree in EEWS (Energy, Environment, Water and Sustainability) from Korea Advanced Institute of Science and Technology (KAIST) in 2011, and Bachelor’s Degree in Materials Science and Engineering from Hanyang University in 2009. At LBNL, Dr. Kim runs Renewable Energy Storage Lab, which designs and develops efficient and cost-effective energy storage and conversion materials based on the fundamental understanding of synthesis-structure-performance relationships. More information about Dr. Kim and his research group can be found here: https://kimhaegyeom1.wixsite.com/kim1

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High-Performance Neuromorphic Computing Based on One-Dimensional Halide Perovskites

Neuromorphic computing, inspired by the structure of the human brain, aims to overcome the limitations of traditional computing architectures by more closely integrating processing and memory functions. It is believed that this approach is a step towards dramatically improving the efficiency of artificial neural networks by in-memory computing. Specifically, compared to conventional graphics processing units, the memristor crossbars connected by synapses would markedly enhance the training and inference of the artificial neural networks in terms of speed and power for natural language processing, image classification, and so forth.

Due to their tantalizing properties, including unique control of ionic processes, mechanical flexibility, and low cost processability, organic materials, such as small molecules, polymers, graphene oxides, and halide perovskites, have sparked considerable research interests for crossbar memristive materials for artificial neural networks. Nevertheless, some weaknesses, such as dissatisfactory environmental stability, irreproducible switching behavior, and lack of understanding of the switching mechanisms, inevitably limit their applications for such application. Thus, it is of vital importance to rationally design new organic materials for crossbar memristors and synapses, to thoroughly understand their mechanisms, and to characterize their performance.

Recently, Vishwanath et al. designed, fabricated, and evaluated one-dimensional halide perovskites for crossbar memristive materials for application in artificial neural networks. They synthesized two kinds of one-dimensional halide perovskites, one with the organic cation of propylpyridinium and the other with the organic cation of benzylpyridinium. The substituted pyridines were used as templating agents to construct the one-dimensional structures. Compared to the three-dimensional perovskites, these exhibit better resistive switching performance due to their larger band gaps.

Figure 1: Comparative evaluation of 1D halide perovskites (PrPyr)[PbI3] and (BnzPyr)[PbI3]. Single crystal X-ray structures of 1D lead-iodide hybrids (A) (PrPyr)[PbI3] and (B) (BnzPyr)[PbI3]. Grey, blue, and purple spheroids represent C, N, and I atoms, respectively, while the cyan octahedron represents the [PbI6]−4 coordination sphere. Insets show the molecular structures of PrPyr+ and BnzPyr+ cations. H atoms are omitted for clarity. Thermal ellipsoids are shown at 50% probability. (C) Glancing angle X-ray diffraction (GAXRD) patterns, (D) UV-vis absorption spectra, and (E) I–V characteristics demonstrating the resistive switching effect in three different perovskites, MAPbI3, (PrPyr)[PbI3] and (BnzPyr)[PbI3]. (F) Crystal structure of (BnzPyr)[PbI3] where the edgeto-face type π-stacking interactions of aromatic cores are highlighted with dashed lines within the organic galleries. The square insets show a view down the axis from the perspective of eclipsed aromatic cores (viewing direction is denoted by the black arrows, while the red arrows point to the C atoms containing C–H ‘‘H-bond donor’’ functionalities). Reproduced from DOI: 10.1039/d3mh02055j with permission from the Royal Society of Chemistry.

In order to maximize the improvement of their reliability, endurance, and retention, a device configuration of Ag/PMMA/HP/PEDOT:PSS/ITO was adopted, in which the halide perovskites switching matrix is sandwiched between the poly(methyl methacrylate) (PMMA) isolated layers and the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). By employing the widely-used solution-processable technique, the team elaborately fabricated the largest dot point and crossbar halide perovskites memristive arrays so far (50000 devices across an area of 100 cm2 and 16×16 crossbar).

Furthermore, they comprehensively analyzed the analog programming window for the halide perovskites. Concurrently, a spiking neural network with halide perovskite synapses was trained to classify the handwritten digits from the Modified National Institute of Standards and Technology database, which corroborates the applicability of the spike-timing-dependent plasticity learning of one-dimensional halide perovskite memristive synapses.

In summary, this novel study pioneers a new path for high-performance neuromorphic computing with innovative halide perovskites as the active material. These insightful results not only offer a solid foundation for the future explorations of halide perovskites in state-of-the-art neuromorphic computing, but also highlight the significance of materials innovation in unlocking the potential of next-generation computing technologies.

To find out more, please read:

High-performance one-dimensional halide perovskite crossbar memristors and synapses for neuromorphic computing
Sujaya Kumar Vishwanath, Benny Febriansyah, Si En Ng, Tisita Das, Jyotibdha Acharya, Rohit Abraham John, Divyam Sharma, Putu Andhita Dananjaya, Metikoti Jagadeeswararao, Naveen Tiwari, Mohit Ramesh Chandra Kulkarni, Wen Siang Lew, Sudip Chakraborty, Arindam Basuf and Nripan Mathews
Mater. Horiz., 2024, Advance Article, DOI: 10.1039/d3mh02055j


About the blogger


 

Wen Shi is currently an Associate Professor at School of Chemistry, Sun Yat-sen University and a Materials Horizons Community Board member. He received his Ph.D. in physical chemistry from Tsinghua University in 2017. From 2017 to 2021, he worked as a scientist at Institute of High Performance Computing (IHPC), Agency for Science, Technology and Research (A*STAR) in Singapore. Dr. Shi’s current research interests are in theoretical computations and simulations of functional materials.

 

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Processing Myco-Composites Through Sustainable Additive Manufacturing

In the ever-evolving landscape of materials engineering, researchers are pushing the boundaries of sustainability and functionality. One groundbreaking avenue of exploration is the integration of mycelium, the root-like structure of fungi, into biocomposites. In this blog post, we delve into a recent study that harnesses the unique properties of mycelium through 3D printing and indirect inoculation, resulting in a material with enhanced mechanical strength and diverse applications.

Shen et al. formulated a biocomposite designed to offer mechanical robustness and compatibility with mycelium. To achieve this, the researchers ingeniously selected chitosan and cellulose and introduced leftover coffee grounds as a sustainable source of nutrients. This careful combination created a material that not only exhibited shear thinning behavior, ideal for 3D printing but also laid the foundation for mycelium colonization (Figure 1).

One distinguishing feature of this study is the use of indirect inoculation for mycelium colonization. Traditionally, direct inoculation involves mixing the inoculum with the composite material before printing. However, the researchers chose a different route, incubating printed samples on a bed of live mycelium. This indirect approach, although taking longer for full colonization, turned out to be more effective.

The study of the mechanical properties of biocomposites revealed a strong influence on the orientation of the 3D printing tool path and the alignment of the cellulose fibers. The authors printed parts of different shapes, and the mechanical properties were dependent on the printing design. However, the fully colonized material showed a notable increase in mechanical strength, surpassing previously reported mycelium composites.

 

Figure 1. (A) Keeping the solid:liquid ratio consistent, the introduction of spent coffee grounds augmented the rate of mycelium colonization up to a threshold (B) The optimized biocomposite displays shear-thinning characteristics, offering advantages for extrusion-based additive manufacturing. (C) Achieving a vertical resolution of approximately 2 mm. Adapted from DOI: 10.1039/D3MH01277H with permission from the Royal Society of Chemistry

The influence of mycelium extended beyond mechanical properties to wettability and absorption characteristics. The fully colonized composite developed a smooth hydrophobic “skin,” demonstrating improved water contact angles. Under submerged conditions, the colonized compound demonstrated lower water absorption and volume swelling, attributed to the presence of hydrophobic mycelial hyphae.

The team explored the capabilities of mycelium to develop biosealed mycelium containers as self-sealing living boxes and the creation of flexible textile-like materials through precise 3D printing and mycelium colonization. By printing biocomposite panels with consistent gaps and allowing mycelium to cover them, flexible hinges were formed, enabling the creation of a material capable of bending and stretching in multiple directions.

In conclusion, the fusion of 3D printing, indirect inoculation, and mycelium colonization represents a leap forward in the field of sustainable biocomposites. The mechanical properties, wetting characteristics, and adaptability of the biocomposite open avenues for green alternatives in packaging, textiles, and more.

To find out more, please read:

Robust myco-composites: a biocomposite platform for versatile hybrid-living materials
Sabrina C. Shen, Nicolas A. Lee, William J. Lockett, Aliai D. Acuil, Hannah B. Gazdus, Branden N. Spitzerab  and Markus J. Buehler
Mater. Horiz., 2024, Advance Article, DOI: 10.1039/D3MH01277H


About the blogger


 

Dr. Danila Merino is the PI of the SusBioComp group at POLYMAT and a Materials Horizons Community Board member. Her research focuses on the development of new sustainable biocomposite materials derived from biomass specifically designed to protect and enhance agricultural and food systems with minimal environmental impact.

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Using a liquid-liquid interfacial route in the production of anodes for aqueous sodium-ion batteries

To address the need for large-scale electrochemical energy storage (EES), much research attention has moved beyond Li-ion batteries due to safety and security-of-supply issues. Sodium, an alkali-metal which is much more abundant and well-distributed globally, is of keen interest as its mining process is cleaner and freer from ethical concern. Moreover, to avoid the high flammability of organic electrolytes, some researchers are looking towards aqueous sodium-ion batteries as a potential contender for future EES systems. This has the added benefit of increasing the ionic conductivity by as much as two orders of magnitude versus organic equivalents, potentially enabling higher rate capability. However, moving from traditional carbonate-based electrolytes to water means a narrowing of the electrochemical stability window and the need for electrodes to facilitate the intercalation and de-intercalation of hydrated cations. Given the smaller accessible voltage and the larger charge carrier, aqueous sodium-ion batteries are still plagued by low specific energy and limited lifespans.

Therefore, the development of new electrode materials to maximise specific capacity is an important research direction. For the anode material, much attention has been paid to the development of polyanionic materials, such as sodium superionic conductors (NASICON), but also carbon-based materials such as polypyrrole and polyimide systems. In recent work by Maria K. Ramos et al., however, the synthesis of a graphene-based composite thin-film was presented, incorporating two compounds that had been shown to have high capacities but suffered from low conductivity and significant volume changes.

Specifically, the researchers highlighted the difficulty of producing ternary thin-films by traditional fabrication routes (e.g., spin-coating, vapour deposition etc.), spurring the development of a liquid-liquid interfacial route (LLIR) for the self-assembly of materials at the interface of immiscible liquids to give a continuous network that can be deposited on any solid substrate. MoS2, known to facilitate the intercalation and de-intercalation of hydrated sodium ions, and non-toxic copper oxide nanoparticles with high theoretical specific capacity, were combined with graphene in this way to produce ternary films that were electrochemically characterised.

Interestingly, the researchers detailed three different thin-film preparation approaches using their LLIR method (Figure 1). The in-situ approach, whereby graphene oxide and Cu2+ were simultaneously reduced in a dispersion of MoS2, yielded a thin-film anode material that demonstrated a very high specific capacity of 1377 mA h g-1 (c.f. specific capacity of typical lithium-ion batteries is < 200 mA h g-1).

Figure 1: Schematic representation of the general steps for thin-film preparation of: (a) MoS2; (b) rGO/CuxO or rGO; (c) rGO/MoS2 and rGO/CuxO/MoS2 layer-by-layer; (d) rGO/MoS2 and rGO/CuxO/MoS2 mixing; and (e) rGO/MoS2 and rGO/CuxO/MoS2 by an in-situ method. Reproduced from DOI: 10.1039/d3mh00982c with permission from the Royal Society of Chemistry.

In summary, the successful implementation of this in-situ liquid-liquid interfacial method for thin-film preparation provides encouragement for its use to produce other composite electrode materials, and a greater understanding of its scalability. The demonstration of such a high-capacity aqueous sodium-ion battery electrode should encourage greater exploration of this more sustainable, beyond-lithium EES technology.

To find out more, please read:

Nanoarchitected graphene/copper oxide nanoparticles/MoS2 ternary thin films as highly efficient electrodes for aqueous sodium-ion batteriesMaria K. Ramos, Gustavo Martins, Luiz H. Marcolino-Junior, Márcio F. Bergamini, Marcela M. Oliveira and Aldo J. G. Zarbin
Mater. Horiz., 2023, 10, 5521-5537, DOI: 10.1039/d3mh00982c


About the blogger


 

Dr Josh J Bailey is an Illuminate Fellow at Queen’s University Belfast, focused on the implementation and optimisation of ionic liquids used in polymer electrolyte fuel cells and is a Materials Horizons Community Board member. He received his doctoral degree from University College London, UK, as part of the Centre for Doctoral Training in Advanced Characterisation of Materials, investigating electrode degradation in solid oxide fuel cells. His research interests span fuel cells, lithium-ion batteries, solid-state batteries, and flow batteries, both in terms of the design of novel electrodes, electrolytes, and membrane materials, as well as the study of materials degradation, with a view to improving performance and durability.

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Rebirth of biomass technology for functional materials through supramolecular upcycling

For a considerable period, the engine of progress was fuelled primarily by economic incentives. However, this paradigm has shifted due to increased awareness of the environmental consequences of society. Focus has turned towards embracing sustainability as a precursor to assimilating the fruits of progress into industry. This trend leverages the conversion of different waste feedstock like plastics, metals, etc, into new added value matter. The added value matter could be fuels, solvents, organic substrates, new polymers, and functional materials.

Embracing the notion that “the new is often the well-forgotten old,” the use of biomass as a feedstock for materials with practicable qualities has been revisited and revitalized. The biomass is feedstock mainly derived from agricultural and forestry resources, and animal resources. Compared to other waste feedstock, such as plastic, electronic, and construction waste, biomass already fits more within the sustainable economic strategy due to its natural origin. The other side of this coin is the insufficient mechanical properties of biomass-derived materials which leads to poor durability and recyclability of functional materials from biomass.

Recent work from Leixiao Yu, Lingyan Gao, Shengyi Dong and team suggests a supramolecular strategy to overcome these limitations. They reported the conversion of 6 types of biomass (cellulose, guar gum, sericin protein, chitin, corn protein and potato starch) to functional materials via copolymerization with thioctic acid (TA) to afford poly[TA-biomass]. The material formation is driven by hydrogen bonding between TA and the polar functional groups in the biomass. Despite such non-covalent forces being reversible and inherently weaker than covalent bonds, prepared materials are proven to be highly impact resistant. The prepared poly[TA-biomass] is highly adhesive and water-resistant, however, it could be fully depolymerized by simple ethanol treatment and involved in the next cycle of polymerization-utilization without any obvious decay in mechanical strength. This anticipates potential applications of poly[TA-biomass as anti-water, impact resistant materials. The team expanded the potential application directions to the biomedical field by demonstrating high biocompatibility, nontoxicity, and antimicrobial effects towards both gram-positive and negative bacteria, attributed to TA. For instance, the newly prepared poly[TA-biomass] may hold promise for smart packaging or wound healing materials.

Figure 1:Chemical structures of biomass (upper block,) and preparation of poly[TA-biomass]s via supramolecular approach – formation of hydrogen bonding hydrogen bonding between thioctic and the polar functional groups in the biomass (middle block) and key advantages of poly[TA-biomass]s materials. Reproduced from DOI: 10.1039/d3mh01692g with permission from the Royal Society of Chemistry.

This recent work is a perfect example of the “waste to wealth” approach, where materials chemistry assisted in transforming common feedstock into functional materials. Combining waste feedstock with a supramolecular strategy is a promising concept that can be broadened to the use of other types of feedstock (plastic, metal) and a broad family of non-covalent interactions (hydrogen bonding, π- π stacking, hydrophobic effects). At the moment, however, this research directs the attention of the community to biomass as a promising feedstock for functional materials design.

To find out more, please read:

A supramolecular approach for converting renewable biomass into functional materials
Yunfei Zhang, Changyong Cai, Ke Xu, Xiao Yang, Leixiao Yu, Lingyan Gao and Shengyi Dong
Mater. Horiz., 2024, Advance Article, DOI: 10.1039/D3MH01692G


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Dr Olga Guselnikova is a member of the Materials Horizons Community Board. She recently joined the Center for Electrochemistry and Surface Technology (Austria) to work on functional materials as a group leader. Dr. Guselnikova received her PhD degree in chemistry from the University of Chemistry and Technology Prague (Czech Republic) and Tomsk Polytechnic University (Russia) in 2019. Her research interests are related to surface chemistry for functional materials. This means that she is applying her background in organic chemistry to materials science: plasmonic and polymer surfaces are hybridized with organic molecules to create high-performance elements and devices.

 

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Improving MoO2-based water-splitting electrocatalysts by incorporating Fe

As we progress towards sustainable sources of energy, achieving efficient hydrogen generation through water splitting becomes increasingly vital. However, the challenges associated with electrode and membrane degradation due to corrosion in seawater hinder large-scale applications. While indirect seawater splitting through pre-desalination can circumvent corrosion issues, it introduces a drawback demanding additional energy input, rendering it economically less attractive. Therefore, the development of cost-effective water splitting electrocatalysts is essential for making the overall electrolysis process economically viable for widespread adoption and industrialization. Metal oxide electrocatalysts with active site engineering is a cutting-edge strategy to obtain high activity and durable catalysts for long-lasting performance under harsh saline conditions.

Recent work by Meng and team presents heterogeneous spin state molybdenum dioxide (MoO2) as a promising electrocatalyst to address the above critical challenges. Their novel approach involves the incorporation of Fe into MoO2 nanosheets on Ni foam (Fe-MoO2/NF) through a rapid carbothermal shocking method. This synthetic process facilitates the lattice dislocations, effectively exposing rich O vacancies and inducing a low-oxidation state in Mo sites, especially during the rapid Joule heating process. This results in the manipulation of spin states between Fe and Mo atoms. The resulting catalyst demonstrates remarkable performance for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline seawater.

The integration of heterogeneous spin states into MoO2 disrupts the d–d orbital coupling resulting in modified electronic configuration. This significantly affects the binding energy between the active sites and reaction intermediates, thereby enhancing the electrocatalytic activity. The catalytic activity of Fe–MoO2/NF is demonstrated by ultralow overpotentials recorded for both HER (17 mV@10 mA cm−2) and OER (310 mV@50 mA cm−2). Furthermore, the catalyst exhibits high selectivity in alkaline seawater splitting, showcasing its potential for efficient hydrogen production in challenging environmental conditions. To demonstrate the practical applicability of this newly developed electrocatalyst, the Fe–MoO2/NF is assembled into an anion exchange membrane seawater electrolyser that achieves a low energy consumption of 5.5 kW h m−3, emphasizing its practical application in renewable energy systems.

Figure 1: (A) Synthesis scheme of Fe–MoO2 /NF; SEM and TEM image along with HRTEM images and Schematic representations of lattice distortion formation mechanism of incorporated heterogeneous spin state (B) DFT analysis of the optimized models of MoO2, Fe–MoO2 and charge density difference plot of Fe–MoO2 (C) HER, OER and AEM electrolyzer polarization curves in saline water with long-term HER stability measurements in alkaline seawater solution. Reproduced from DOI: 10.1039/D3MH01757E with permission from the Royal Society of Chemistry.

An important aspect of this research is the successful coupling of Fe–MoO2/NF with a solar-driven electrolytic system, yielding a solar-to-hydrogen efficiency of 13.5%. This demonstrates the catalyst’s compatibility with solar energy, opening avenues for sustainable and clean hydrogen production. Theoretical insights into the electronic structure of Fe-incorporated MoO2, along with the abundance of oxygen vacancies, provides a deeper understanding of the catalytic mechanisms involved. Distortion of the Mo–O bonds, optimized through this method, plays a crucial role in enhancing the binding energy of adsorbed species during the electrochemical processes.

Looking forward, these findings hold significant promise for practical water splitting at a scalable level, especially in the context of solar-to-hydrogen production. The successful integration of Fe–MoO2/NF into a solar-driven electrolytic system is a critical step toward sustainable and eco-friendly widespread adoption and integration into large-scale hydrogen production systems. In the pursuit of practical water splitting for solar-to-hydrogen production on a larger scale, the key challenge lies in making the process economically viable and technologically feasible. Thus, the prospects for this work include optimizing the synthesis method and extending for other heterogeneous spin such as Ni and Co for seawater splitting, which might extend the versatility of the proposed strategy, offering a simple and efficient approach for efficient electrocatalysts. The simplicity and efficiency of the proposed strategy make it an attractive option for large-scale implementation. As the demand for green energy solutions and the reduction of carbon footprints continue to grow, the significance of advancements in water-splitting, especially saline water electrolysis driven by solar energy, cannot be overstated. This study adds to the growing body of evidence that renewable energy sources can be used to produce hydrogen, which will pave the ways towards a more greener and sustainable energy future.

To find out more, please read:

Rapid carbothermal shocking fabrication of iron-incorporated molybdenum oxide with heterogeneous spin states for enhanced overall water/seawater splitting
Jianpeng Sun, Shiyu Qin, Zhan Zhao, Zisheng Zhang and Xiangchao Meng
Mater. Horiz., 2024, Advance Article, DOI: 10.1039/D3MH01757E


About the blogger


 

Shahid Zaman is currently a postdoctoral fellow at Hydrogen Research Institute, University of Quebec Trois-Rivières, Canada, and he is a Materials Horizons Community Board member. He received his Ph.D. in Material Physics and Chemistry from Huazhong University of Science and Technology in 2021. From 2021 to 2023, he worked as a postdoctoral fellow at the Southern University of Science and Technology, China. Dr. Shahid’s current research interests are nanomaterials for electrocatalysis in proton exchange membrane fuel cells and water electrolyzers.

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Towards a personalized therapy for peripheral nerve injuries

Peripheral nerve injury is a common complication of surgical procedures and traumatic insults that can result in severe discomfort including chronic pain and sensory defects. Ensuring that the injured nerve regenerates is therefore critical for the long-term well-being of affected individuals. A promising therapeutic strategy to enhance regeneration is to target both the initial inflammation and subsequently promote axonal regrowth. How to deliver drugs sequentially and on time for each patient is a complex engineering challenge requiring innovative solutions.

Toward this end, Shan and the team developed a stimuli-responsive drug delivery scaffold for a dual drug delivery that makes it possible to target both inflammation and axonal sprouting sequentially. The team created a composite material that consists of a Poly-L-lactic acid (PLLA) shell that provides mechanical support to the regenerating axons and that can be loaded with the novel bioactive and stimuli-responsive scaffold.

Figure 1. Schematic illustration of the structure and drug release process of the responsive cascade drug delivery scaffold (RCDDS) for peripheral nerve injury repair. (A) A brief illustration of the structure of the RCDDS implanted in SD rat. (B) Drug release process of the RCDDS and the corresponding repair stage. Vitamin B12 loaded in the hydrogel system can be adjustably released in the early stage by ultrasound to alleviate inflammation, while NGF loaded in alginate microspheres and PLGA nanoparticles can be gradually released from the RCDDS to promote axon regeneration one month after implantation. Reproduced from DOI: 10.1039/D3MH01511D with permission from the Royal Society of Chemistry

To achieve a staggered drug release profile, the team encapsulated vitamin B12 (vB12) with anti-inflammatory properties directly inside calcium crosslinked alginate hydrogel and used an additional multilevel encapsulation approach consisting of microspheres loaded with nerve growth factor (NGF)-adsorbed nanoparticles enabling their delayed release compared to vB12. The team then leveraged ultrasound as a stimulus to hierarchically open polymer chains in ultrasound-responsive calcium cross-linked alginate hydrogels.  The rate of release of both vB12 and NGF was not predetermined and could be tuned by changing ultrasound intensity thus enabling the adjustment of the delivery profiles based on the individual patient’s healing progress. Interestingly, the ultrasound treatment alone improved peripheral nerve regeneration by promoting the secretion of neurotrophins in rodent models. Taken together, Shan and colleagues developed a novel strategy to promote nerve repair which utilizes ultrasound as an easily administrable stimulus that makes it possible to adjust the treatment of injured peripheral nerves based on patient’s needs.

To find out more, please read:

A responsive cascade drug delivery scaffold adapted to the therapeutic time window for peripheral nerve injury repair
Yizhu Shan, Lingling Xu, Xi Cui, Engui Wang, Fengying Jiang, Jiaxuan Li, Han Ouyang, Tailang Yin, Hongqing Feng, Dan Luo, Yan Zhang and Zhou Li
Mater. Horiz., 2024, Advance Article, DOI: 10.1039/D3MH01511D

 


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Anna Stejskalova is currently a postdoctoral fellow at the Wyss Institute at Harvard Medical School and a member of the Materials Horizons Community Board. Dr. Stejskalova’s research focuses on female reproductive health and preterm birth utilizing organs on a chips and advanced biomaterials.

 

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