Biodegradable ink revolutionizes eco-friendly sensors


In a recent article published in the journal scientific reportResearchers from Itay have proposed the production and operation principles of paper-based sensors using biodegradable polylactic acid (PLA) emulsion ink. The main goal of the research is to explore sustainable electronic device manufacturing through the use of environmentally friendly materials such as carbon nanotubes (CNTs) and silver (Ag) flakes.

Biodegradable ink revolutionizes eco-friendly sensors
Schematic diagram of the pressure sensor manufacturing process. Image Source: https://www.nature.com/articles/s41598-024-60315-z

This innovative approach aims to alleviate the e-waste problem and promote a circular economy in the electronics industry. By utilizing PLA and conductive fillers, the research aims to demonstrate the potential of green electronics and their application in sensor technology, in line with the increasing emphasis on eco-conscious practices across industries.

background

Piezoresistive sensors are typically made from materials whose resistance changes with mechanical stress or strain. Traditional sensor components are often composed of non-biodegradable materials, leading to environmental degradation and accumulation of electronic waste.

To address these sustainability challenges, researchers are exploring alternative materials such as PLA and sustainable conductive fillers such as CNTs and silver flakes. Developing paper-based sensors by incorporating these environmentally friendly elements will be critical to demonstrate the feasibility of creating biodegradable electronic devices with enhanced sustainability and performance characteristics, thereby promoting the advancement of green technologies.

Current research

Start the experimental procedure by dissolving PLA 6060D in 20 mL of ethyl acetate. Subsequently, the PLA dispersion is emulsified by adding a nonionic surfactant to disperse the oil in water. In order to maintain the equivalent weight of PLA and polyurethane dispersion (PUD) after drying, aqueous polyurethane was introduced into the polymer emulsion containing 1% wt. People’s Liberation Army.

Conductive inks containing multi-walled carbon nanotubes (MWCNTs), silver flakes, graphene nanoparticles (GNPs), or mixtures of silver flakes and GNPs or MWCNTs were integrated into PLA/PUD emulsions at a ratio of 30% wt. relative to polymer concentration. The resulting mixture was probe sonicated for 3 min to ensure uniform dispersion of the filler.

The PLA concentration is adjusted for applications requiring higher viscosity materials, such as screen printing or 3D printing. Vary the binder to filler ratio to achieve the desired conductivity level. Optimize the duration of tip sonication to promote even distribution of fillers within the emulsion.

Various coating techniques for depositing conductive inks onto substrates were evaluated. Spray coating was chosen for its scalability and low polymer consumption to evenly apply the conductive ink to the substrate. This method ensures consistent coating thickness and coverage, which is critical for sensor fabrication and evaluation.

The fabricated sensors and coatings were characterized using techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Raman spectroscopy to analyze the performance of the materials and coatings.

Results and discussion

The study successfully formulated an emulsion ink based on PLA and incorporated sustainable fillers, which exhibited good adhesion and conductive properties. SEM imaging provided insight into the morphology of the coating, while EDS analysis confirmed the presence of the desired elements in the material. XRD patterns elucidate the crystal structure of the ingredients, and Raman spectroscopy provides valuable information about the chemical composition.

Dynamic light scattering was used to determine the average droplet size of the emulsion, while infrared spectroscopy provided insight into the material’s chemical properties. Thermogravimetric analysis (TGA) and surface mapping further enhance understanding of ink formulations. Coating techniques, specifically spraying, have proven effective in uniformly depositing conductive inks onto substrates.

The addition of carbon nanotubes, silver flakes, and graphene nanoparticles significantly enhances the conductivity of the PLA-based emulsion ink, making it suitable for sensor applications. By adjusting the ratio of binder to filler, researchers can tailor the ink’s conductivity to meet specific application requirements. The utilization of sustainable materials and the development of efficient coating technologies highlight the potential of environmentally friendly ink formulations in additive manufacturing and sensor technology, paving the way for enhanced sustainability in the production of electronic devices.

in conclusion

In summary, this study presents a pioneering approach to develop paper-based sensors using biodegradable PLA emulsion ink rich in sustainable conductive fillers. The successful integration of eco-friendly materials such as carbon nanotubes and silver flakes highlights the feasibility of creating green electronic devices with enhanced functionality and reduced environmental impact.

By optimizing ink formulations and coating methods, this research helps advance additive manufacturing technology toward more sustainable and efficient solutions. The findings not only demonstrate the potential for environmentally friendly electronics and sensor applications, but also highlight the key role of sustainability in shaping the future of the electronics industry and promoting the adoption of greener, more environmentally friendly methods of manufacturing electronic devices.

Journal reference

Najafi, M., Forestier, E., Safarpour, M. et al. (2024). Biodegradable polylactic acid emulsion ink based on carbon nanotubes and silver for printing pressure sensors. scientific report 14.10988.



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