Establishing a long-term presence on the moon will require solving challenges that are easy to overlook on Earth. Lunar temperatures, for instance, can vary from hundreds of degrees below zero to boiling, making effective insulation essential for lunar habitats.
But many materials that excel at slowing heat transfer are not designed to withstand the bumps, compression and repeated handling that would likely come with building and maintaining infrastructure on the moon.
Now, engineers at the University of Pennsylvania are exploring a surprisingly simple alternative: stacking hundreds of sheets of Mylar , the same lightweight plastic used as household food wrap and, when coated with aluminum, the shiny emergency blankets handed out after marathons to conserve runners’ body heat.
In a new paper in ACS Applied Materials & Interfaces , the team describes a novel way of assembling the film, which they call hybrid layered insulating film stacks (HyLIFS), and which join two properties that rarely co-occur: strong thermal insulation and mechanical durability.
“These stacks of Mylar can bend, withstand substantial compression and maintain their insulating performance,” says senior author Igor Bargatin , Associate Professor in Mechanical Engineering and Applied Mechanics (MEAM), “potentially allowing them to be packed, transported and survive rough treatment over many years of use.”
If the technology can scale from the lab to mass production, the material could prove essential for everything from lunar habitats to spacesuits and other technologies that must operate for long periods of time in the vacuum of space.
“The combination of thermal and mechanical robustness is critical for long-term use on the moon,” notes first author Danielle R. Levin , a recent Penn doctoral graduate in chemistry, who also received a master’s in MEAM. “This material could open a pathway to inexpensive, durable and reusable lunar insulation.”
When Good Insulation Isn't Strong Enough
For insulation designed to work in a vacuum, keeping heat from moving through the material is only part of the challenge.
Some of today's best-performing insulation materials are extremely fragile. Aerogels, for example, are lightweight materials composed largely of empty space. That structure makes them excellent insulators of everything from industrial pipelines to NASA’s Mars rovers , but can also leave them vulnerable to mechanical damage.
Other materials work well until they are compressed or damaged. Multilayer insulation, another technology commonly used in space, relies on reflective films separated by insulating spacers. It is highly effective at limiting heat transfer from radiation but is not designed to bear significant loads and tears easily when touched.
That creates a fundamental trade-off: Making an insulator mechanically stronger can come at the expense of its thermal performance. “For lunar infrastructure, we would ideally like both,” says Bargatin. “The ideal material is both resistant to damage and to the loss of heat.”
Stacking Layers of Mylar
The Penn team's approach starts with Mylar, formally known as biaxially oriented polyethylene terephthalate, or BoPET, a familiar polymer already widely used in aerospace applications, as well as the blankets given to marathon runners post-race. When combined with a metal like aluminum, Mylar blocks infrared radiation, trapping heat.
The researchers tested Mylar films of several thicknesses, coating some with an extremely thin layer of aluminum oxide, also known as alumina, to increase stiffness. They then stacked the films, one sheet at a time. "At the moment, the process is very time-consuming,” says Levin. “We use two pairs of tweezers and small weights to handle and stack the delicate films. Even breathing near the stack can send the layers flying.”
When tested in a vacuum, that simple construction produced a material with an unusual combination of properties. Compressed the way it would likely be in a lunar habitat that contains air at atmospheric pressure indoors, the best-performing stacks reached thermal conductivity comparable to other high-performance vacuum insulation technologies while remaining flexible.
In separate mechanical tests, coated stacks maintained their thermal performance even under the highest compressive dresses achievable with the lab's equipment. In other words, the researchers did not have to choose between making the material a good insulator and making it durable.
Putting the Layers Under Pressure
Even Levin did not expect the films to be quite so sturdy. The researchers repeatedly compressed samples to approximately 20 megapascals, roughly equivalent to concentrating 200 pounds onto the area of a fingertip. “We were concerned about the material failing under such high compressive stress," recalls Levin. "But the stacks didn't survive just one high stress cycle — they survived 10 in a row."
That durability could have an important practical benefit beyond outlasting an accidental impact in space. Anything needed for construction on the moon must first be transported there, making flexibility and reusability important considerations for lunar infrastructure.
“You could use these stacks to insulate a lunar habitation, but astronauts will inevitably have little accidents where they bump into them,” notes Bargatin. “When we're talking about long-term habitation on the moon, it's really important to have tough materials that can last long enough.”
A Tiny Particle With an Outsized Role
The study also revealed that an overlooked feature of commercial Mylar could be central to understanding how these stacks work.
Extremely thin plastic films tend to cling to themselves and other surfaces, making them difficult to manufacture and handle. To prevent that, manufacturers incorporate microscopic “antiblocking” particles in the material. These particles protrude slightly from the surface, helping keep adjacent layers from sticking together.
The existence and industrial purpose of the particles were already known. What had received little attention, according to the researchers, was the particles’ role in transferring heat through stacked Mylar films.
Because conventional multilayer insulation is designed primarily to limit radiative heat transfer, there has been less reason to examine whether these tiny particles constrain pathways for conductive heat transfer between sheets.
To investigate that possibility, the researchers developed models of heat transfer across the interfaces between sheets and compared the models with experimental data. Their results suggest that, in a vacuum, heat primarily crosses from one sheet to another at the microscopic points where antiblocking particles touch neighboring films.
That insight could help design even better insulation: Instead of treating the particles simply as an unavoidable feature of commercial Mylar, future materials could potentially be engineered with the particles’ size, number and distribution specifically chosen to control heat transfer.
Thinner Isn’t Always Better
The particles also helped the researchers make sense of one of the study's more counterintuitive results.
Initially, the team expected the thinnest films to provide the best insulation; thinner films allow more layers, and therefore more interfaces that limit heat transfer, to fit into the same space.
Instead, the team’s thinnest successfully characterized films and the films of medium thickness performed similarly when coated with alumina.
The researchers believe the reason lies partly in those antiblocking particles in the thinner films, which create more contact between neighboring layers and additional pathways for heat to flow.
That means optimizing the insulation is more complicated than simply making each layer as thin as possible. “As you compress the layers the contact landscape changes,” says Levin. “It’s not just a matter of minimizing the film thickness or the number of particles; we must also account for how the contacts change and the films deform as pressure increases.”
In short, film thickness, stiffness and the distribution of embedded particles all influence thermal performance.
From Hand-Stacked Samples to Lunar Habitats
For now, the HyLIFS samples are small, about one square centimeter in area, and time-consuming to produce, with manual cutting and stacking taking hours.
Scaling that process to the meter-sized sheets needed for practical insulation will ultimately require a different approach, but the researchers point to manufacturing techniques that could suffice, like continuously coating large rolls of Mylar.
Eventually, it might be possible to tune the film thickness, coating and antiblocking particle distribution before winding the material into large stacks.
Questions remain about how the films would behave at those larger scales, including whether they can survive the multiple bending cycles as well as bumps and scuffs of real-life applications. But if the films’ small-scale properties hold, the material could prove invaluable as flexible insulation in lunar habitats, rovers, electronic systems and more.
For Levin, the work demonstrates how much can still be learned from materials that engineers think they know well. "The simplest configuration ended up being the best one," she says.
This study was conducted at the University of Pennsylvania School of Engineering and Applied Science (Penn Engineering). Additional co-authors include Matthew F. Campbell , Gulzhan Aldan , Orevaoghene H. Omodior .
This work was supported by the National Science Foundation Division of Chemical, Bioengineering, Environmental and Transport Systems (grant number 1845933) and Penn Engineering.
ACS Applied Materials & Interfaces
Experimental study
Not applicable
Robust Layered Thermal Insulator Film Stacks for Vacuum Applications
16-Sep-2026
The authors declare no competing financial interest.