Nanoparticle aggregates can be plastically deformed with heat

May 15, 2026

Researchers make nanoparticle aggregates heat moldable using ionic liquid cations, preserving particle shape and crystallites during thermoforming.

(Nanowerk News) Researchers at The University of Osaka have created heat moldable nanoparticle aggregates that soften and reshape when warmed while keeping the individual particles intact (Science Advances, “Thermoforming nanoparticle aggregates via interfacial ionic self-diffusion”). The team attached anionic groups to the surfaces of cellulose nanofibers and paired them with cations drawn from an ionic liquid; at elevated temperatures the cations migrate along the interfaces between fibers, allowing the aggregate to expand and take a new shape. The work appears in Science Advances.

Key Findings

Aggregates of nanoparticles, meaning material particles between one and one hundred nanometers in size, can deliver high mechanical strength, low thermal expansivity, and high thermal conductivity. Those properties make them attractive for lightweight automotive components and for heat dissipating parts inside electronic devices. Getting them into useful shapes economically, however, has remained an obstacle that limits where they can be deployed. Thermoforming, in which a material is heated until pliable and then pressed into a target shape, is a low-cost manufacturing route widely used for conventional plastics. Nanoparticle aggregates have resisted this kind of processing because heating them tends to distort the particles, disrupt their crystalline order, or trigger decomposition or oxidation, eliminating the very properties that made the aggregates useful in the first place. Material design for thermoplasticization of nanoparticle aggregates. (A) Introduction of ionic liquid cations onto the wood-derived nanoparticle (CNF) surfaces. (B) Thermoplasticization mechanism of its aggregates. (Image: Reproduced from DOI:10.1126/sciadv.aeb3281, CC BY) The Osaka team focused on cellulose nanofibers derived from wood pulp. They attached negatively charged anionic groups to the fiber surfaces and balanced them with positively charged cations drawn from an ionic liquid, defined as a salt that remains liquid below 100 °C. With this surface chemistry in place, the aggregates softened and expanded under heat rather than degrading, and could be pressed into shape. “Aggregates of the prepared CNFs expanded considerably upon heating,” explains lead author Shun Ishioka. “This is the first time nanoparticle aggregates have been thermoformed while preserving the particle shape and crystallites in the material. The sheets of thermoformable CNF aggregates have high strength and low thermal expansivity under ambient conditions, unlike conventional thermoplastics.” Ionic materials generally show greater ion mobility once they enter a thermoplastic state, and the Osaka measurements followed that pattern. At elevated temperatures, cations migrated along the interfaces between adjacent cellulose nanofibers, and that interfacial motion coincided with bulk expansion of the aggregate. The findings tie thermoplastic behavior in these materials directly to dynamics at the contact regions between particles. To test whether the approach reaches beyond cellulose, the team applied the same surface ion treatment to graphene oxide, a two-dimensional carbon nanoparticle with very different geometry and chemistry. “We used our strategy to thermoform a system of two-dimensional carbon nanoparticles (graphene oxide),” reports Tsuguyuki Saito, senior author. “Thus, the strategy may be applicable to diverse systems.” Choosing different surface ions gives researchers a handle on both the mechanical and thermal characteristics of the aggregate and on its ability to be shaped under heat. The Osaka authors position the approach as a route to nanomaterial substitutes for petroleum derived and metal based thermoplastics, and as a way to dial in property combinations for specific structural and thermal management roles.