Revolutionary ‘MOCHI’ Material Promises Energy-Efficient Windows and Beyond
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A new transparent insulating material developed by researchers at the University of Colorado Boulder could dramatically reduce energy loss through windows – a major contributor to global energy consumption. Dubbed MOCHI, or Mesoporous Optically Clear Heat Insulator, the material offers a potential solution to a long-standing engineering challenge: creating a window that insulates as well as a wall, but remains clear like glass.
Worldwide, buildings account for roughly 40% of total energy use, with a significant portion wasted keeping indoor spaces comfortable. Despite typically covering only about 8% of a building’s exterior, windows are responsible for nearly half of the heat transfer. In modern homes featuring expansive glass surfaces, this fraction can be even higher. Existing solutions like vacuum-insulated glass and transparent aerogels often prove costly, difficult to manufacture at scale, or suffer from reduced clarity as thickness increases.
The core challenge lies in the structure of insulating materials. Effective insulation often relies on trapping air, but inconsistent pore sizes can scatter light and allow heat to pass through. An ideal insulator requires pores smaller than the wavelength of visible light and smaller than the distance air molecules travel before colliding – approximately 60 nanometers at room temperature.
A “Frozen Air” Breakthrough
Researchers at CU Boulder believe they’ve cracked the code with MOCHI, a material that behaves like a highly controlled version of “frozen air.” The material traps heat while remaining almost invisible to the naked eye. MOCHI’s structure consists of a network of hollow silicone nanotubes arranged in a remarkably uniform pattern. More than 90% of its volume is air, held stable and evenly spaced by a solid framework comprising just 5% to 15% of the material. This precise composition achieves both low heat flow and high transparency.
Testing revealed that thin sheets of MOCHI transmit over 99% of visible light with minimal haze, surpassing the typical 92% transmission rate of ordinary window glass. Simultaneously, MOCHI conducts heat at less than half the rate of still air. “To block heat exchange, you can put a lot of insulation in your walls, but windows need to be transparent,” explained Ivan Smalyukh, a physics professor at CU Boulder and senior author of the study published in the journal Science. “Finding insulators that are transparent is really challenging.”
From Lab to Large-Scale Production
One of the most promising aspects of MOCHI is its scalability. The research team has successfully produced square-meter-sized films and slabs several centimeters thick without compromising clarity or insulation. These slabs can be integrated into insulated glass units (IGUs), mirroring the thickness of standard double-pane windows.
When implemented in this way, MOCHI-filled windows achieved insulation levels comparable to, and in some cases exceeding, well-insulated walls. Even thin layers applied to single-pane windows significantly improved performance, bringing them close to double-pane standards. Infrared imaging confirmed substantially reduced heat leakage compared to conventional windows.
Beyond thermal performance, MOCHI offers additional benefits. By blocking thermal radiation, it minimizes condensation and dampens sound. Tests demonstrated a noise reduction of up to 35 decibels at certain frequencies, outperforming standard double-pane glass.
The Science Behind the Structure
The manufacturing process relies on controlled self-assembly. Researchers combine silicone precursors with surfactant molecules that naturally form microscopic threads in solution. Silicone coats these threads, and subsequent steps replace the surfactant with air, resulting in a dense network of microscopic air-filled tubes. Smalyukh likened the structure to a “plumber’s nightmare,” but one that functions exceptionally well for insulation.
Under a microscope, MOCHI differs significantly from traditional aerogels. Instead of random clumps with irregular gaps, it exhibits an orderly network of uniform pores. This structure allows light to pass through with minimal scattering, thanks to a refractive index close to that of air, minimizing surface reflection.
Because the pores are smaller than the mean free path of air molecules, heat transfer is dramatically slowed. Gas molecules collide with the pore walls rather than each other, limiting energy exchange. The silicone framework itself further resists heat flow. In thicker slabs, MOCHI absorbs and reemits thermal infrared radiation, further reducing heat loss.
Harnessing Sunlight for Energy Generation
MOCHI’s potential extends beyond simple insulation. The material allows visible and near-infrared sunlight to pass through while trapping longer-wavelength heat radiation. When paired with a dark absorber, MOCHI allows sunlight in but retains much of the heat. Experiments showed MOCHI-covered absorbers reached temperatures near 300 degrees Celsius under regular sunlight, and continued to collect usable heat even on cloudy days. Simulations suggest that incorporating these panels into a home’s exterior could meet heating needs, with larger installations potentially generating surplus energy.
Durability tests indicate MOCHI-based products could last at least 20 years, comparable to conventional IGUs. Samples adhered to interior window surfaces survived five years in real-world conditions, including exposure to dust, acid rain, and chemicals, without losing key properties. The material is mechanically robust, can be rolled into thin films, laser-cut into complex shapes, and remains superhydrophobic, fire retardant, and water-repellent, according to Smalyukh.
Implications for the Future of Building Design
MOCHI has the potential to revolutionize building energy management. By transforming windows into high-performance insulators, architects could incorporate more glass into designs without sacrificing efficiency. This could lead to reduced heating and cooling demands, lower energy bills, and decreased emissions. Beyond buildings, potential applications include greenhouses, protective clothing, and solar thermal systems.
While currently a laboratory product, the ingredients for MOCHI are relatively inexpensive. Researchers are focused on refining the manufacturing process to enable widespread adoption. If successful, windows may one day cease to be a source of energy loss and instead contribute to energy generation.
Research findings are available online in the journal Science.
