In modern society, the continuous emergence of new electronic devices has led to a significant amount of old electronic equipment not being effectively recycled. The destruction process of these devices can easily generate toxic substances harmful to both humans and the environment. However, a university in the United States has developed a new type of recyclable and repairable circuit board, which holds the potential to reduce the generation of electronic waste and toxic materials.
People nowadays are constantly seeking to upgrade their electronic products such as smartphones, computers, and home appliances, leading to a large number of old devices becoming “e-waste”. The recycling of electronic waste involves a labor-intensive process, with difficulties in recycling circuit boards and some plastics. The low return rates and profits further complicate the recycling efforts, contributing to the continuous growth of electronic waste.
According to a report released by the United Nations in 2024, the global volume of electronic waste has rapidly increased from 340 billion kilograms to 620 billion kilograms over the past 12 years. This weight is equivalent to 1.55 million transport trucks, and it is projected to reach 820 billion kilograms by 2030. Only 20% (approximately 138 billion kilograms) of this waste can be effectively recycled and reused, indicating a potentially ongoing issue.
Virginia Tech in the United States has developed a new type of electronic circuit material known as LM-Vitrimer, featuring recyclability, conductivity, reconstructability, and self-repair capabilities. This innovative circuit board also retains the strength and durability of traditional circuit board plastics. The research was published on June 1 in the journal “Advanced Materials”.
The research team utilized a dynamic glassy polymer Vitrimer as the base material and combined it with low-melting-point liquid metal (LM) droplets to synthesize the new circuit board (LM-Vitrimer). The entire process requires no additional catalysts or high curing temperatures, making the shaping and reshaping process simple.
The Vitrimer polymer provides qualities such as rigidity, thermal stability, mechanical properties, and recyclability similar to plastics for the LM-Vitrimer circuit board, while the EGaIn liquid alloy (75wt.% gallium, 25wt.% indium) imparts good electrical conductivity, allowing for circuit planning and current direction.
Testing on the mechanical strength and conductivity of the LM-Vitrimer composite material showed promising results. A 1.5 millimeter thick LM-Vitrimer circuit board could withstand a tensile force of 9 kilograms, even when bent into a spiral, maintaining normal electrical operation and supporting stable current and voltage transmission.
Researchers synthesized Vitrimer to create a “pure ester-based epoxy Vitrimer” to test its malleability, mechanical properties, and stability. The material exhibited high stability, withstanding a maximum tensile strength of 80 MPa and enabling reshaping between temperatures of 170°C to 200°C while maintaining excellent mechanical performance.
Furthermore, the team tested the self-repair capability of LM-Vitrimer circuit boards, demonstrating their durability even when damaged. They only required brief heating to restore shape and electrical functionality.
LM-Vitrimer circuit boards can be degraded post-life cycle using a 5 M sodium hydroxide (NaOH) solution, allowing for the recovery of key components like Vitrimer, EGaIn liquid alloy, and LED bulbs. These components can be reassembled into new circuit boards, leaving behind minimal unprocessable byproducts.
The research team highlighted that while they cannot control the quantity of electronic products disposed of globally, this invention can prevent more electronic products from ending up in landfills. Their future research aims to achieve complete recycling and reuse of LM-Vitrimer materials and other components.
Michael Bartlett, Associate Professor of Mechanical Engineering at Virginia Tech, stated, “Our material differs from traditional electronic composites. Even under mechanical deformation or damage, these LM-Vitrimer circuit boards can continue to function normally, showcasing their exceptional elasticity and functionality.”
Assistant professor Joshua C. Worch from Virginia Tech’s Institute for Critical Technology and Applied Science and Bartlett National Science Foundation Career Award supported this research.