In a recent article published in Advanced Sustainable Systems, researchers developed an all-natural alternative to plastic straws using a top-down molecular welding approach. This straw is made from de-lignified natural wood infused with chitosan, resulting in a flexible, moldable material that can be shaped as needed.
Study: Lightweight, Strong, Hydrostable, Bendable, Rolled-Up, and Biodegradable Straws Enabled by Nano- and Microarchitecture Tuning of the Wood Cell Wall and Molecular Welding Strategy. Image Credit: prph.photo/Shutterstock.com
Background
Plastic straws are widely used consumer products, prompting significant efforts to develop biodegradable alternatives to replace petroleum-based plastics. However, existing options like polylactic acid and paper straws come with notable drawbacks, making them less-than-ideal substitutes.
To effectively replace plastic straws, there is an urgent need for biodegradable, environmentally friendly materials that offer both mechanical durability and water resistance. Researchers have explored bottom-up approaches to create cellulose-based straws from biomass sources such as wood, bamboo, and bagasse.
These methods typically involve chemical treatments, mechanical disintegration, and high-pressure homogenization. However, these multi-step processes are resource-intensive, requiring substantial chemical, energy, and water inputs—making them less sustainable.
In contrast, top-down fabrication offers a more efficient solution. By preserving the natural structure of bio-based materials, this approach enhances water resistance and mechanical strength with minimal processing, aligning more closely with sustainable manufacturing goals.
Methods
To fabricate the all-natural straws, a delignified wood slice was first cut into strips (3×15 cm) and immersed in a chitosan solution. The chitosan gradually infiltrated the wood’s microporous structure through repeated degassing cycles at 100 Pa (3 minutes per cycle). Once infused, the chitosan-infiltrated wood strips were rolled around stainless-steel sticks (5.5 mm in diameter) and air-dried at room temperature.
To enhance the straws' stability in water and beverages, they were further dehydrated at 150 °C for two hours, a process that also removed residual acetic acid through thermal volatilization. Additionally, a water-morphing technique was applied to create an accordion-like bendable joint, increasing the straw’s flexibility.
The structural properties of the natural wood, delignified wood, and final straw products—including both straight and bendable versions—were analyzed using field emission scanning electron microscopy (FESEM). Tensile stress-strain profiles were recorded with a universal testing machine to assess mechanical performance.
To examine the material’s crystalline structure and chemical modifications, X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) were conducted before and after delignification. Small-angle X-ray scattering (SAXS) analysis provided further insights into the material’s internal structure. Finally, cytotoxicity and fluorescence-based live/dead assays were performed to evaluate the potential biological effects of the all-natural straw on cultured cells.
Results and Discussion
FESEM imaging revealed that the all-natural plastic substitute featured conformal chitosan layers on both the outer surface and inner vessel channels. This compact chitosan deposition significantly enhanced mechanical strength and hydro-stability due to the strong chitosan-cellulose interface and chitosan’s inherent hydrophobicity.
SAXS analysis further confirmed that the cellulose nanofibers remained anisotropically aligned, contributing to the material’s high mechanical properties. The final all-natural straws were precisely controlled to measure 10 cm in length, with an inner diameter of 5.5 mm and an outer diameter of 5.7 mm.
Mechanical testing showed that the all-natural plastic substitute was 5.5 times stronger than natural wood slices, 12.4 times stronger than polypropylene, and 18.8 times stronger than wax-coated paper. Additionally, its average toughness was 5.8 times higher than that of natural wood slices.
After baking, the all-natural straw demonstrated exceptional hydro-stability in carbonated beverages, remaining intact and un-delaminated even after two days of immersion in a pH 2.6 carbonated drink.
Cytotoxicity testing showed that the all-natural straw extract had lactate dehydrogenase (LDH) levels similar to the negative control (clean culture medium) and significantly lower than the positive control (Triton X-100). This indicates that the straws did not release any cytotoxic substances. In contrast, natural wood extract had a higher LDH level, suggesting that delignification effectively removed cytotoxic components from wood.
The accordion-like bendable version of the all-natural straw, produced through a water-moldable process, exhibited reversible bendability up to 120°. Even when compressed to 50% of its original length, the straw fully recovered without surface cracks, with only the crease wavelength changing from 18 mm to 9 mm.
Conclusion
Overall, the researchers successfully prepared microplastic-free, ultra-strong, hydro-stable, and biodegradable all-natural bendable straws through a top-down method using earth-abundant natural wood and edible chitosan.
The all-natural straws offer several key advantages, including high flexural, compressive, and tensile strengths, excellent stability in water and beverages, biocompatibility, recyclability, biodegradability, and cost-effectiveness—at just $0.002 per straw. Additionally, they can be produced with an optional bendable feature for added convenience.
Unlike commercial straw materials such as polylactic acid, polypropylene, and polyhydroxyalkanoate—which can take hundreds of years to decompose—these all-natural straws provide a truly environmentally friendly alternative while also outperforming traditional options in mechanical strength and having a lower mass density.
Another significant advantage is that existing paper straw manufacturing machines can be adapted to produce these all-natural straws, making large-scale production feasible and supporting their adoption in the consumer market.
Journal Reference
He, S. et al. (2025). Lightweight, Strong, Hydrostable, Bendable, Rolled‐Up, and Biodegradable Straws Enabled by Nano‐ and Microarchitecture Tuning of the Wood Cell Wall and Molecular Welding Strategy. Advanced Sustainable Systems. doi: 10.1002/adsu.202400737.https://onlinelibrary.wiley.com/doi/10.1002/adsu.202400737
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