Sandro Stucki

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Stucki

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Sandro

ORCID

0000-0001-8348-2540

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Publications1 - 10 of 17

Iron-Catalyzed Laser-Induced Graphitization Enabling Current Collector-Free Electrodes With Spatially Tunable Iron/Iron Oxide Phases
Dreimol, Christopher; Edberg, Jesper; Kürsteiner, Ronny; et al. (2025)
Advanced Materials
Iron-catalyzed laser-induced graphitization (IC-LIG) represents an eco-efficient alternative to traditional carbon electrode manufacturing. Combining a bio-based tannic acid-iron precursor ink with CO₂ laser treatment results in sheet resistance of 23.59 ± 1.2 Ω square⁻¹ on renewable substrates. Varying the tannic-acid-to-iron ratio (TA:Fe), the rheology of the precursor ink can be tuned, enabling versatile application techniques, including spray coating, screen printing, and direct-ink-writing (DIW). Subsequent laser-treatment enables the formation of functional IC-LIG electrodes for all application methods, while even thick DIW-printed layers (260 μm) result in complex, conductive electrode patterns. Laser post-treatment expands design possibilities by locally tuning iron phases, such as converting γ-iron to magnetite. The unidirectional laser-treatment results in a layered arrangement, forming a multilayer electrode with a highly graphitized top layer serving as a current collector substitute, and an underlying composite of iron-rich nanoparticles embedded in a porous graphitic foam, acting as a hybrid electrode. Electrochemical analysis reveals double-layer capacitor behavior at low TA:Fe ratios, while higher ratios demonstrate increased redox activity and pseudo-capacitive characteristics. Achieving stable capacities of 15 mF cm⁻² with a 1 M NaCl electrolyte over 5000 cycles underscores the potential of IC-LIG electrodes as a sustainable solution for advanced energy storage devices and beyond.
Investigations on Wood- and Wood-Hybrid-Joints and their Moisture Stability
Stucki, Sandro (2024)
Wood is a highly valued, renewable resource with excellent mechanical properties. However, the natural heterogeneity of wood and its dimensional restrictions limit the use of wood in its natural state. Engineered wood products (EWP) have been developed to overcome or improve those limitations by assembling smaller wood pieces into larger structures. Especially adhesive-bonded EWPs allow for increased utilization of wood in construction and can be tailored for specific requirements, such as mass timber for structural application (e.g. glulam, CLT, etc). Nowadays, mass timber is mostly manufactured from softwood species. However, as a result of a changing climate, a shift towards mixed forests with an increased share of more stress-resistant hardwood species is expected. Therefore, the wood industry is required to adapt its products and processes toward increased utilization of hardwood species, to ensure sustainable and efficient wood usage in the future. Thus, in this work, hardwood-based wood-concrete hybrid systems were investigated with the potential to increase the integration of hardwood into the current building industry. Furthermore, an alternative production process called linear friction welding for adhesive-free bonding of wood was explored, with a focus on improving the water stability of welded wood joints. The implementation of beech wood in the building sector was approached through the development of two different adhesive-bonded timber-concrete composite (TCC) systems. The combination of timber with concrete allows for high-performing structures by taking advantage of the high tensile strength of beech wood and the stiffness and compression strength of concrete. By avoiding tensile forces in the concrete, steel reinforcements therein can be minimized or omitted, leading to structures with reduced environmental impact and suitable mechanical properties for structural application. In the first part, beech wood was adhesive-bonded to mortar using the wet-in-wet process (i.e. fresh mortar is poured on uncured adhesive). For the bonding, a hybrid adhesive consisting of a mixture of silane-terminated polymers (STP) with an epoxy resin, was investigated. The combination of these two adhesives extends the functionality of either adhesive chemistry by itself and results in a rather elastic silane network with good bonding performance of the silane groups to both, the organic wood and the inorganic mortar, with the epoxy resin providing the strength and stiffness of the adhesive that is necessary to transfer shear stresses across the bondline, allowing the full exploitation of the composite action. The STP-epoxy hybrid adhesive proved to be suitable for the bonding of mortar to beech wood in the wet-in-wet process, fulfilling the bond strength requirements for use in II structural applications. Water immersion tests showed a limited, though adequate, short-term moisture stability of the TCC for potential use in interior environments. In the second part, mortar and adhesive were replaced by polymer concretes (PC) for the fabrication of TCCs. PCs exhibit high tensile and compression strength, allowing the omission of steel reinforcements. Two different PC chemistries, epoxy- and PUR-based binder, were investigated, with the epoxy-based PC showing superior bonding performance to beech wood in both, dry and wet states compared to PUR-PC. Investigations on the influence of wood swelling upon changing moisture conditions using digital image correlation (DIC) showed different deformation behaviour of epoxy- and PUR-PC bonded specimens, with the epoxy-based PC stabilising the wood-PC interface and distributing the swelling strain into the bulk of the wood, whereas the PUR-PC failed in the PC near the interface due to the swelling-induced stresses. The third part of this thesis focuses on an alternative wood bonding process called linear friction welding, which allows the bonding of wood without adhesives by thermal activation of the wood's inherent components. However, such wood bonds are no alternative to synthetic adhesives yet, partially due to their low moisture stability which limits their field of application. In this work, different biopolymers were investigated as sustainable bonding additives to increase moisture stability. Lignin of different origins and chemical modifications thereof showed the importance of the molecular structure and chemical functionalities. Softwood kraft lignin with a high polydispersity index and high molecular weight proved to be the most promising additive, achieving a moderate increase in wet strength and avoiding delamination after water storage This thesis shows that hardwood species, represented by beech wood, have the potential to be employed in TCCs for manufacturing EWPs for structural applications and that both, mortar and polymer concretes, can be bonded to beech wood with suitable bond performance for use in interior environments. Linear friction welding of spruce wood with lignins as a bonding additive proved to be a promising approach for a sustainable bonding technique for wood. Moderately improved moisture stability using lignin as a renewable bonding additive was achieved, albeit the achieved improvement is not yet sufficient to seriously compete with synthetic adhesives. Furthermore, the use of lignins showed promising behaviour to facilitate the upscaling of the wood welding process.
Thermoresponsive Smart Gating Wood Membranes
Ding, Yong; Panzarasa, Guido; Stucki, Sandro; et al. (2022)
ACS Sustainable Chemistry & Engineering
Smart membranes that can open and/or close their pores in a controlled manner by external stimuli possess potential in various applications, such as water flow manipulation, indoor climate regulation, and sensing. The design of smart gating membranes with high flux, immediate response, and mechanical robustness is still an open challenge, limiting their versatility and practical applicability. Inspired by the controlled opening and closure of plant stomata, we have developed a smart gating wood membrane, taking advantage of the unique wood scaffold with its hierarchical porous structure to carry thermoresponsive hydrogel gates. Laser drilling was applied to cut channels in the wood scaffold with well-aligned pores to incorporate the smart gating membranes. In situ polymerization of poly(N-isopropylacrylamide) above its lower critical solution temperature inside the channels resulted in a hydrogel with a heterogeneous microstructure acting as a thermoresponsive gate. The wood-based smart gating membranes exhibited reversible and stable pore opening/closing under heating/cooling stimuli. The achieved rapid response and feasibility of scale-up open the venue for various practical applications. In this work, we demonstrated their potential for indoor light regulation and as a water flow manipulator.
Renewable wood-phase change material composites for passive temperature regulation of buildings
Leibnitz, Oskar; Dreimol, Christopher; Stucki, Sandro; et al. (2024)
Next Materials
The buildings sector consumes a significant amount of raw materials and energy resources, with high-energy consumption and environmental impact. To achieve net-zero emissions, it is crucial to address the substantial carbon footprint generated by buildings in operation. A promising solution lies in the development of renewable and sustainable building materials capable of efficiently storing thermal energy to regulate indoor temperature without relying on operational energy (HVAC systems). Here we report on a wood-phase change material (PCM) composite, referred to as PCM-wood, which holds potential for energy-efficient buildings. The composite shows excellent thermal regulation capability with a melting enthalpy of 113 J g−1 at 22 °C and solidification enthalpy of 114 J g−1 at 21 °C. Despite some loss of mass and in enthalpy of melting, the PCM-wood showcases stable thermal regulation performance over 50 heating/cooling cycles and the wood modification does not negatively impact the tensile strength of the wood material. Hence, the PCM-wood composite combines structural performance and efficient energy storage with the ability to passively regulate indoor temperature, buffering fluctuations of more than 6 °C. Such a passive thermal regulation strategy has the potential to significantly reduce energy consumption in the building sector and to help achieve net-zero buildings by reducing energy consumption and mitigating CO2 emissions.
Natural Wood-Based Catalytic Membrane Microreactors for Continuous Hydrogen Generation
Tu, Kunkun; Büchele, Simon; Mitchell, Sharon; et al. (2022)
ACS Applied Materials & Interfaces
The development of controlled processes for continuous hydrogen generation from solid-state storage chemicals such as ammonia borane is central to integrating renewable hydrogen into a clean energy mix. However, to date, most reported platforms operate in batch mode, posing a challenge for controllable hydrogen release, catalyst reusability, and large-scale operation. To address these issues, we developed flow-Through wood-based catalytic microreactors, characterized by inherent natural oriented microchannels. The prepared structured catalysts utilize silver-promoted palladium nanoparticles supported on metal-organic framework (MOF)-coated wood microreactors as the active phase. Catalytic tests demonstrate their highly controllable hydrogen production in continuous mode, and by adjusting the ammonia borane flow and wood species, we reach stable productivities of up to 10.4 cmH23 min-1 cmcat-3. The modular design of the structured catalysts proves readily scalable. Our versatile approach is applicable for other metals and MOF combinations, thus comprising a sustainable and scalable platform for catalytic dehydrogenations and applications in the energy-water nexus.
Bonding of beech wood to mortar with a novel epoxy hybrid-adhesive: Performance in dry and wet conditions
Stucki, Sandro; Kelch, Steffen; Mamie, Tim; et al. (2025)
International Journal of Adhesion and Adhesives
Composites made of timber and cementitious materials require a rigid connection to exploit their full composite action, which can be achieved by using full-surface adhesive bonding. In this work, we investigated a novel hybrid-adhesive system consisting of a silane-terminated polyurethane (STP) and epoxy resin for the bonding of beech wood timber to fresh mortar for use in timber-mortar composites (TMC). The mechanical performance and the influence of moisture on TMC produced by the wet-in-wet process (fresh mortar) was investigated and compared to the bonding of prefabricated mortar (prefab process). The STP-epoxy hybrid-adhesive showed a suitable bonding performance of beech wood to both, fresh mortar and precured mortar with median compression shear strengths of 4.57 MPa and 6.07 MPa, respectively. The fracture pattern showed the strength of the near-surface layer in the mortar, close to the adhesive, being often decisive for the bond performance. The same failure mode predominated in TMC beams after 3-point bending tests. The stability of the composite upon the influence of moisture is especially challenging when using beech wood due to its low dimensional stability. Thus, the moisture stability of the bond was investigated by compression shear tests after water immersion. It showed an improved water stability compared to composites bonded with an epoxy resin. Nonetheless, a clear reduction in bond strength compared to the dry state was observed, with delamination of 25 % of the wet-in-wet and 17 % of the prefab specimens during water immersion. Furthermore, it was seen that the adhesive open laying time played a decisive role in the wet-in-wet produced specimens influencing both, dry and wet shear strength.
Split wooden rods for novel wood-based boards in the construction sector
Burgert, Ingo; Kegel, Sebastian; Schnider, Thomas; et al. (2024)
RILEM Technical Letters
Wood has been utilized as a building material for thousands of years. Nowadays, its renewable nature and carbon-storing capacity can become important factors in climate change mitigation efforts. This has led to a resurgence of timber engineering in recent years, with impressive multi-story timber buildings worldwide. However, it should not be overlooked that the wood sector will face several challenges in the coming years and decades to pave the way to a leading role of wood in the desired transition toward bioeconomy. Based on the assumption that an increasing demand for wood will make it a more precious resource, a couple of strains will emerge across the entire value chain of wood processing. This calls for innovations to address issues arising from predicted changes in resource provision, to increase material yields, and to promote reuse after the end of life. Our conceptual article proposes a new wood separation and processing method. This approach is inspired by the well-known production of wood shingles and is currently being developed for the implementation of new wood-based products.
Functionalized wood with tunable tribopolarity for efficient triboelectric nanogenerators
Sun, Jianguo; Tu, Kunkun; Büchele, Simon; et al. (2021)
Matter
Wood is a state-of-art, renewable, and sustainable building material with excellent mechanical properties but negligible triboelectric polarizability. Strategies to improve and rationally tune the triboelectric properties of wood are needed to further its application for mechanical energy harvesting in smart buildings. We found that wood becomes more triboelectrically positive when modified by in situ-grown zeolitic imidazolate framework-8 (ZIF-8), a metal-organic framework (MOF), and more triboelectrically negative when coated with poly(dimethylsiloxane) (PDMS). A triboelectric nanogenerator (TENG) made with two radial-cut wood samples (L x R x T: 35 x 20 x 1 mm(3)), respectively functionalized with ZIF-8 and PDMS, can generate an open-circuit voltage (Voc) of 24.3 V and a short-circuit current (Isc) of 0.32 mu A upon 50 N, 80 times higher compared with that of native wood. We demonstrate the applicability of our functionalized wood TENG (FW-TENG) in smart buildings by using it to power household lamps, calculators, and electrochromic windows.
Scalable and sustainable wood for efficient mechanical energy conversion in buildings via triboelectric effects
Sun, Jianguo; Schütz, Urs; Tu, Kunkun; et al. (2022)
Nano Energy
Triboelectric nanogenerators (TENG) have great potential to help enhancing the energy efficiency of buildings, and thus to contribute significantly to the reduction of global greenhouse gas emissions. However, there are major barriers against the adoption of such emerging energy technologies. Meeting the need for sustainable large-scale fabrication of high-performance products remains a critical challenge towards real-world TENGs’ building applications. To mitigate this challenge, we enhance the poor polarizability of native wood by a scalable plasma treatment, a facile approach which to the greatest degree preserves wood's warm colors, mechanical robustness while efficiently enhancing the triboelectric output. We demonstrate the enhancement of electric output by assembling wood triboelectric nanogenerators (W-TENGs) in both contact-separation and single-electrode operation modes. We show that when two radial-cut wood samples (L × R × T: 100 × 80 × 1 mm3), one treated with an O2 plasma and the other with a C4F8 + O2 plasma, are subjected to periodic contact and separation with an applied pressure as low as 0.0225 MPa, a maximum voltage of 227 V and a current of 4.8 µA are produced. Eventually, we showcase the real-world applicability of our approach with two prototypes of triboelectric wood floors, opening up new technological pathways towards a ‘net-zero emissions’ future.
Biofabrication and performance of mixed-density mycelium modules
Bitting , Selina; Rossi, Vita; Möwes , Hannah; et al. (2025)
Structures and Architecture ~ Structures and Architecture. REstructure REmaterialize REthink REuse
The construction industry heavily relies on non-renewable materials with linear life cycles, which contribute to the growing issue of waste generation. As the global demand for construction continues to increase, there is an urgent need for renewable, circular materials to mitigate these issues. One such material is mycelium-bound composites (MBCs), which combine mycelium with lignocellulosic substrates to create compostable materials with a circular life cycle. The research presented in this paper evaluates the suitability of modular, reusable interior partitions made exclusively from mycelium-based materials. Focusing on acoustic performance and ease of deconstruction, stackable modules were designed which combine dense MBCs with infill MBC. Dense MBC refers to MBCs which have been post-processed into board-like materials through different types of pressing, while infill MBC has not been post-processed. Three key aspects were investigated: the biofabrication method of the module, the strength of the attachment between the materials, and the thermal and acoustic performance of the infill MBC. To develop a reliable biofabrication strategy, pull-apart tests on small attachment samples assessed the connection between infill MBC and different dense materials. These tests qualitatively evaluated the strength of the binding between the infill and dense material to later inform the 1:1 partition module design. Thermal and acoustic tests were performed on cylindrical samples of infill MBC. Preliminary results confirm that the infill material can be implemented as an acoustic or thermal material. The partition module design was then fabricated at a 1:1 scale using both cold-pressed MBC and heat-pressed MBC as the dense material. The findings reveal that a number of challenges and complications in the biofabrication process remain. Pre-treatment of the dense pieces as well as mould design were identified as influential factors in the biofabrication process. Overall, the results show potential for mixed-density mycelium material solutions for short-to medium-term interior applications, thereby reducing the waste from refreshing interior spaces and the raw material demands associated with such redesigns. Contamination prevention remains a key challenge; however, the results show the binding strength between dense and infill materials to be sufficient that a mixed-density mycelium module is feasible.

Publications1 - 10 of 17

Sandro Stucki

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