Wood soaked in oil outperforms 130-year-old transformer insulation by 50%

Every ChatGPT query consumes roughly as much electricity as lighting dozens of incandescent bulbs. As demand for AI data centers surges, scientists have upended the material at the heart of power infrastructure that has gone unchanged for 130 years — and the answer turned out to be wood.

A joint research team from the University of Maryland, Yale University and the University of Texas at Austin published findings in Volume 12, Issue 24 of the international journal Science Advances showing that an insulating material made by saturating wood with oil outperforms conventional insulating paper by up to 1.5 times.

Inside every transformer: a single sheet of paper

Large-scale power generated at a plant travels through transmission lines and transformers (right), where voltage is safely regulated before being distributed to industrial complexes and homes. Transformers serve as the critical junction for stepping voltage up or down. Inside, iron cores and wiring interlock in complex arrangements. The insulating paper — shown in white and brown — forms a tight barrier between the core and the wiring, preventing powerful current from leaking out or causing a short circuit. [Science Advances, Vol. 12, No. 24]

Inside the transformers atop utility poles and within the transmission towers linking power plants to homes sits a sheet of paper whose sole job is to stop electricity from going where it should not. That insulating paper, made from ground wood fiber, has underpinned the power grid's core components since the 1890s — and the material has not changed since.

Conventional insulating paper can withstand up to 72 kilovolts per millimeter — more than 300 times the voltage of a standard household outlet — held back by a single sheet.

The AI era is now pushing that aging material to its limits. Surging data center demand has placed heavier loads on transformers, raising the risk of failure from overheating and insulation breakdown.

The material also dissipates heat poorly. When heat generated inside a transformer cannot escape, internal temperatures climb, and prolonged exposure to high heat causes the paper's fibers to fracture and crumble — ultimately destroying the insulation and taking the transformer with it.

What happens when you soak wood in oil

A comparison of oil distribution and electrical breakdown paths in conventional insulating paper (B) and the newly developed wood-based material (C). Yellow lines trace the paths along which electricity ultimately leaks through the insulator and arcs — paths that should not exist. [Science Advances, Vol. 12, No. 24]

The research team focused on wood's natural structure. Wood fibers are densely aligned in a single direction. Conventional insulating paper destroys that alignment by grinding the fibers down. The team took the opposite approach, preserving the wood's grain structure while boosting its insulating performance.

The manufacturing process is more intuitive than it sounds. Wood is first boiled in a chemical solution to soften its interior, opening up tightly sealed spaces so oil can penetrate. Insulating oil is then forced into those voids under high compression. During that compression step, the oil-filled channels narrow to an average of 166 nanometers — about one five-hundredth the width of a human hair.

A schematic of the manufacturing process for the newly developed oil-impregnated densified wood (ODW). A thin wood veneer undergoes chemical treatment that partially dissolves material between the fibers, creating microscopic voids inside the wood cells. Insulating oil is then drawn into those voids without gaps. The oil-saturated wood is then mechanically compressed under high pressure to densify it. [Science Advances, Vol. 12, No. 24]

The key lies in how the oil-filled channels are arranged. In conventional insulating paper, oil is distributed in a tangled three-dimensional network, giving electricity an easy path to spread through the interconnected passages.

In the new material, aligning the oil channels in a single direction severs those connections. By organizing the channels into parallel rows, the researchers eliminated the discharge pathways electricity could follow — in effect, closing off the alleyways entirely.

Performance proven in numbers

ODW achieved a dielectric strength of up to 105 kilovolts per millimeter — 1.5 times greater than conventional insulating paper — meaning it can withstand far higher voltages at the same thickness.

Its tensile strength reached 384 megapascals, nearly four times that of the conventional material. Steel rebar used in reinforced concrete buildings typically rates around 400 megapascals, meaning the wood-based material in practice matches the structural backbone of rebar.

Temperature distribution maps measured under identical conditions: (F) the newly developed wood insulating material (ODW); (H) conventional insulating paper. [Science Advances, Vol. 12, No. 24]

ODW's ability to shed heat — a transformer's greatest enemy — also improved by more than 1.5 times. When the research team built a transformer using ODW and ran it, the peak internal temperature dropped 10 degrees Celsius compared with a unit using conventional plastic-based material. Lowering a transformer's internal temperature by just 10 degrees dramatically extends its service life.

ODW also proved durable under an accelerated aging test simulating extreme internal conditions, boiling the material at 150 degrees Celsius for six weeks. Conventional insulating paper lost its performance, but ODW retained rigidity 3.6 times higher than the conventional material even after a modest reduction in strength.

Prospects for commercialization

A schematic of the ODW production process for industrial application. [Science Advances, Vol. 12, No. 24]

The research team said ODW can be manufactured using a roll-to-roll process — the same continuous-feed method used to print newspapers and packaging — enabling mass production in long, unspooled sheets.

The team has already produced a large prototype measuring 1.5 meters long and 0.4 meters wide, and the material is flexible enough to be wound around a copper rod.

A large ODW prototype measuring 1.5 meters long and 0.4 meters wide. [Science Advances, Vol. 12, No. 24]

Moving from a published paper to real-world power infrastructure involves significant hurdles. Insulating materials for power transformers require durability validation spanning decades. The accelerated aging test in this study ran for only six weeks, leaving a wide gap between the laboratory results and the long-term verification that decades of field operation would demand.

Reference

DOI: 10.1126/sciadv.aed5744

Meiling Wu et al., "Oil-impregnated densified wood veneer with high electrical insulation enabled by nanosized oil channels." Science Advances 12, eaed5744 (2026).