(Nanowerk Spotlight) The world’s generation of electronic waste is rising at an alarming pace. In 2022 alone, 62 million tonnes of e-waste were produced globally, according to the United Nations’ 2024 Global E-waste Monitor report. To put that into perspective, the sheer volume of discarded electronics would fill 1.55 million 40-tonne trucks—enough trucks to line up bumper-to-bumper around the entire equator. Despite growing awareness of the environmental impact of e-waste, documented recycling efforts are struggling to keep pace, growing five times slower than the rate of waste generation.
This crisis is largely driven by the widespread use of petroleum-based materials in electronics, which are durable but non-degradable, contributing to long-term pollution and resource depletion. To address this, researchers are searching for sustainable alternatives that can meet the functional demands of electronics while minimizing their environmental footprint.
One promising approach is the development of biodegradable materials for electronics. Such materials would allow devices to serve their purpose and then break down naturally, leaving no harmful waste behind. But creating biodegradable electronics is no simple task—especially when it comes to materials that can conduct electricity while being both flexible and robust.
Historically, most electronic components are made from petroleum-based plastics and metals, which provide the necessary mechanical and electrical properties but persist in the environment long after their useful life is over. That’s where the emerging field of transient electronics comes in, which aims to create devices that can perform for a limited time before degrading safely.
A recent study published in Advanced Functional Materials (“Transient Starch-Based Nanocomposites for Sustainable Electronics and Multifunctional Sensing”) explores an innovative solution to this problem: a biodegradable, starch-based material reinforced with a conductive nanomaterial known as MXene. The research represents a significant advance in creating sustainable electronic materials that balance functionality with environmental responsibility.
Starch, a natural polymer derived from plants, has been studied for its potential in green electronics due to its abundance, low cost, and biodegradability. However, starch on its own lacks the electrical conductivity and mechanical strength needed for modern electronic applications. To overcome this, the researchers incorporated MXene, a class of two-dimensional materials made from transition metal carbides and nitrides. MXenes have gained attention for their impressive electrical and mechanical properties, making them ideal for applications in flexible electronics.
In this study, the team combined starch with MXene to form a nanocomposite material, using a water-based process that is both environmentally friendly and scalable. The result was a flexible film with excellent electrical conductivity, mechanical durability, and the ability to degrade in natural environments. This composite material could potentially replace petroleum-based components in a variety of electronic devices, offering a more sustainable alternative without sacrificing performance.
What makes this research particularly exciting is the tunability of the material’s properties. By adjusting the concentration of MXene in the starch matrix, the researchers were able to control the mechanical strength, flexibility, and electrical conductivity of the film. For example, increasing the MXene content from 0.69 to 2.42 volume percent significantly boosted the material’s tensile strength—from 6.4 MPa to 11.2 MPa – while also improving its electrical conductivity. This ability to fine-tune the material’s properties opens up a wide range of potential applications, from sensors and wearable devices to disposable electronics that don’t contribute to long-term waste.
a) Liquid exfoliation of Ti3AlC2 MAX to Ti3C2Tx MXene and SEM image of Ti3C2Tx MXene. b) Preparation of sorbitol-plasticized Ti3C2Tx/starch nanocomposite films, and TEM image of starch/MXene composite film with 0.69 vol% MXene. (Image: Reprinted from DOI:10.1002/adfm.202412138, CC BY)
One of the most promising applications for this starch-MXene composite is in the development of strain sensors – devices that measure physical changes such as pressure, motion, or deformation. Strain sensors are used in everything from fitness trackers to medical devices, and the demand for flexible, high-performance sensors is growing. The starch-based composite developed in this study exhibited excellent sensitivity to strain, making it an ideal candidate for such applications. When the material is stretched or compressed, its electrical resistance changes in a predictable way, allowing it to detect even subtle movements.
The research team tested the material by attaching it to various parts of the body, such as fingers, wrists, and knees, to monitor movement. The composite was able to detect changes in resistance as the body moved, providing precise measurements of bending angles and joint motions. This capability is particularly valuable for wearable health monitors, which require sensitive, real-time tracking of physical activity. In one demonstration, the material detected subtle changes in resistance corresponding to a user’s pulse, highlighting its potential use in medical devices that monitor vital signs.
Beyond health monitoring, the material shows promise for use in tactile sensing and handwriting recognition. The researchers demonstrated that when pressure is applied to the film – such as by writing letters or applying force at specific points – the material responds with distinct changes in resistance. This could pave the way for touch-sensitive surfaces, smart textiles, or digital input devices that recognize hand movements or writing in real-time. For instance, the team wrote letters on the starch-MXene composite and detected unique electrical signals generated by each stroke. This capability could be extended to applications like digital handwriting input or interactive touchscreens.
In addition to its functional advantages, the starch-MXene composite stands out for its biodegradability. One of the major environmental drawbacks of conventional electronic devices is that they persist in the environment for years, contributing to the growing problem of e-waste. The starch-based material developed by Dong and his team degrades rapidly when exposed to natural environments. In soil burial tests, the composite began to break down within nine days and showed significant degradation by day 30. This rapid degradation is driven by microorganisms in the soil that break down the starch matrix. Once the starch decomposes, the MXene particles oxidize, forming environmentally benign byproducts like titanium dioxide (TiO2).
However, while the starch matrix degrades quickly, there are still questions about the long-term environmental impact of MXenes. Although they break down into relatively safe compounds, more research is needed to fully understand their behavior in different ecosystems. Ensuring the safety and sustainability of MXene-based materials across their full lifecycle will be crucial before they can be widely adopted.
The ability of the starch-MXene composite to degrade in natural environments also makes it a promising candidate for transient electronics – devices designed to perform specific tasks for a limited time and then disappear. This concept is particularly valuable in fields like environmental monitoring, where temporary sensors can collect data and then safely degrade without leaving harmful residues. Transient electronics could also play a role in medical applications, such as implants that dissolve after delivering treatment or monitoring a patient’s recovery.
While the starch-MXene composite shows great potential, it is not without its limitations. The material’s relatively low flexibility compared to some other biodegradable polymers could restrict its use in applications that require extensive bending or stretching. The researchers suggest that future work could focus on improving the flexibility of the material by adjusting the plasticizers used in the starch matrix. Achieving the right balance between mechanical strength and flexibility will be key to expanding the material’s applications.
Another challenge lies in the scalability of the production process. Although the water-based manufacturing method is environmentally friendly and relatively simple, scaling up production for industrial use will require further optimization. Nonetheless, the combination of biodegradable starch and high-performance MXene in a single material represents a significant step forward in the development of sustainable electronics.
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