What if a single material could capture energy from sunlight, electricity, and chemical fuels, and hold that charge for months on end? A team at Northwestern University has created exactly that: a liquid that transforms into an electrically conductive black gel when energized, storing electrons in a network of molecular pairs, and returning to liquid when the charge is released.
“This is a remarkable behavior, we have never seen a material that can both harvest and store energy from such different sources,” says Samuel I. Stupp, Board of Trustees Professor at Northwestern and senior author of the study published in Chem.
The work comes from the Center for Bio-inspired Energy Science (CBES), a Department of Energy Energy Frontier Research Center, and represents a fundamentally new approach to energy storage.
The system is built around a custom-designed molecule called ANI-MV, which combines two functional units:
- ANI (an aminonaphthalimide chromophore amphiphile), a light-absorbing, electron-donating unit
- MV (methyl viologen), a well-known electron acceptor and storage unit
In its resting state, these molecules form small globular aggregates suspended in a yellow liquid. When exposed to visible light, a chemical reducing agent, an electrical bias, or even X-rays, the ANI component donates electrons to the adjacent MV units. The reduced MV molecules (radical cations, MV+•) then strongly attract one another, forming electron-storing molecular pairs called pimers, π-radical dimers that stack into semiconducting nanoscale ribbons.
“The pimerization is the key,” explains co-first author Tyler J. Jaynes. “Individual MV radical cations don’t really stick to each other, but the pimer state is highly stable, and that drives the entire self-assembly into a gel.”
The entangled ribbons form an electrically conductive black hydrogel that stores electrons throughout its molecular network. The gel can hold its charge for months under anaerobic conditions, a storage lifetime that rivals many solid-state batteries.
On demand, introducing oxygen triggers a release: the stored electrons react to form reactive oxygen species (ROS) that can drive chemical reactions in complete darkness, a process the team calls “dark photocatalysis.” The gel disassembles back into the yellow liquid, ready to be recharged.
The reversible cycle mimics the dynamic assembly-disassembly of the cell cytoskeleton, but powered by electrons rather than ATP.
Key numbers
The material achieves an electron density of 1.32 × 10⁻³ mole e⁻ per gram of ANI-MV⁺•, comparable to solid-state inorganic semiconductors. One gram, Stupp estimates, could hold enough charge to power a wearable device or smartwatch.
The researchers demonstrated energy capture from four different sources: visible light, chemical fuels (reducing agents), electrochemical bias, and X-rays. Each monomer requires one electron to reach full charge.
The limits
“This is a proof-of-concept, nowhere close to being a practical energy storage system,” cautions Frank Crespilho, a chemist at the University of São Paulo who was not involved in the work, as quoted by Science.
The material has not yet undergone standard battery tests, power output, cycle life, and energy density (Wh/kg) remain unreported. The oxygen-triggered discharge mechanism also means the gel requires anaerobic conditions for storage; open air triggers gradual release, which complicates real-world sealed-device integration.
Scale-up is also unknown. The material exists only at laboratory quantities.
What’s next
The Northwestern team is now working on identifying which microbial metabolites can be isolated to target plasticity without whole-microbiota transplants. “The real prize is understanding what the specific molecules are,” Stupp says. “Then we might be able to design synthetic systems that capture the same energy-storage properties without the complexity of the biological switching mechanism.”
Source
Jaynes TJ, Đorđević L, Sai H, et al. “Dynamic self-assembly mediated by stored and released electrons in pimer supramolecular polymers of chromophore amphiphiles.” Chem, Volume 12, Issue 6, 103075 (2026). DOI: 10.1016/j.chempr.2026.103075
Funding: Center for Bio-inspired Energy Science (CBES), DOE Office of Science, Basic Energy Sciences (Award DE-SC0000989, DE-SC0020884); European Research Council.