Flexible molecular links create new nanoparticle crystals

Both strategies also depend on ligands, molecules that attach to nanoparticle surfaces and link neighboring particles. Researchers have generally made those ligands rigid to preserve predetermined connection angles. The MIT team instead used highly flexible ligands and allowed them to reorganize as the particles assembled.

How does flexibility control the bonds?

Macfarlane’s laboratory had spent years constructing nanoparticles with attached polymer chains. Polymers are large molecules made from repeating smaller units, and their flexibility makes them useful as adjustable molecular connectors.

For the new system, the researchers placed electrical charges at the ends of the flexible ligands. Some carried positive charges and others negative charges. Opposite charges attract, so the connectors bend toward suitable neighboring particles as the system assembles.

That reorganization influences the valency of each nanoparticle, meaning the number of neighboring particles it bonds to. The researchers did not have to specify the direction of every connection in advance. Instead, charge attraction brought compatible ligands together, while their flexibility determined how many connections could form and helped stabilize the resulting structure.

The degree of flexibility and the electrical charges therefore acted as design variables for nanoparticle assembly, rather than serving merely as imperfections to eliminate.

What crystal structures did the researchers create?

Crystals consist of components organized in repeating patterns. In this work, the repeating units were nanoparticles rather than individual atoms or small molecules. Researchers call these ordered nanoparticle networks superlattices.

Sbalbi’s experiments showed that researchers could adjust assembly through two relatively straightforward characteristics: nanoparticle size and the length of each flexible polymer chain. These changes altered the connections formed during assembly and, consequently, the number of neighboring particles linked to each nanoparticle.

By reducing the number of bonds, the team produced more open arrangements rather than the tightly packed structures that commonly form. Macfarlane said: “The amount of flexibility of the polymer dictates how many bonds it has. It allows us to lower the number of bonds each particle has and make lattices we have never seen before.”

What could designer materials accomplish?

A long-term goal in materials science is to select a nanoparticle for its electrical, optical or chemical characteristics and then place it in an arrangement suited to a specific application. That would give researchers independent control over the properties of the individual particle and the structure formed by many such particles.

Existing assembly techniques have not achieved that separation reliably. Macfarlane said the nanoparticle assembly community has aspired to independent control over particle type and final structure, but that ideal had not become reality.

The flexible-connector method may narrow that gap by creating a wider range of arrangements without the elaborate manufacturing steps required by conventional approaches. Potential uses include:

• Photonics, or the control and manipulation of light: Ordered nanoparticles could help engineers produce materials with specialized optical properties.
• Chemical catalysis, in which substances accelerate reactions: New particle arrangements could improve how catalysts operate.
• Electronics, medicine, energy, agriculture and chemical manufacturing: More open formations could combine the individual capabilities of nanoparticles in useful ways.

The team also sees the approach as a possible route toward producing customizable materials at larger scales, which could help move nanoparticle technologies beyond laboratory experiments and into practical use.

What remains before practical use?

The work establishes an assembly strategy rather than a finished commercial technology. The researchers said further development will be necessary to translate the method into applications, and the source report did not establish performance in a specific device or manufacturing process.

The partial funders were the National Science Foundation, the Department of Energy, the U.S. Army and the U.S. Navy. The forthcoming paper, “Breaking symmetry in nanoparticle superlattices via spontaneous valency,” lists Sbalbi, Kronenberger, Shinzawa, Ye, Jayaraman and Macfarlane as its authors. Nature Materials lists the 2026 paper under DOI 10.1038/s41563-026-02787-0.

The work turns molecular bending from a manufacturing liability into a design variable.