Ice Lithography: A Gentle Approach

The Mizzou team has refined a technique known as ice lithography, enabling them to etch incredibly small, detailed patterns directly onto fragile biological surfaces. This method offers a significant advantage over traditional lithography,which,while widely used in manufacturing tiny circuits for electronics,can damage delicate materials.

Traditional lithography relies on liquid processes that can easily harm sensitive materials like carbon nanotubes and biological membranes. Mizzou’s ice-based approach replaces liquid with a layer of frozen ethanol,providing a gentler and more precise way to manipulate materials previously deemed too fragile.

Instead of using a traditional lithography process, which can be too harsh on delicate biological materials, our technique applies a thin layer of ice to protect the material’s surface while the pattern is made.
Gavin King,professor of physics and study co-author

King further explained that that frozen layer helps keep everything stable during the process and makes it possible for us to work with delicate biological materials that would normally be damaged substantially.

Ethanol Ice: A Unique Advantage

Mizzou boasts one of onyl three labs globally, and the only one in North America, employing this specific ice lithography method. The distinguishing factor is the use of ethanol ice, which safeguards delicate biological materials that regular water ice would damage.

To validate their ethanol-ice-based method, the researchers utilized Halobacterium salinarum, a microorganism known for its purple protein that captures sunlight and converts it into energy, functioning similarly to a natural solar panel. This microbe, well-studied since the 1970s, efficiently converts light into energy, making it a promising candidate for developing novel power sources.

Potential Applications: From Microbes to Solar Panels

While Mizzou’s discovery serves as a proof of concept, the team envisions significant future potential, including the possibility of harnessing these delicate purple membranes to create solar panels.

The Process Unveiled: How Ice Lithography Works

The ice lithography method involves several key steps:

• Preparation: The biological membrane is placed on a cold surface inside a scanning electron microscope.
• Cooling: the temperature is reduced to extremely cold levels, below -150°C.
• Ice Formation: Ethanol vapor is introduced, instantly freezing into ethanol ice and forming a thin, smooth layer over the membrane.
• Patterning: A focused beam of electrons draws tiny patterns in the frozen layer.
• Sublimation: The surface is gently warmed, causing the parts of the ice not hit by the beam to sublimate away, leaving the patterned solid material behind.

The patterns we’re making are smaller than 100 nanometers wide, and more than 1,000 times thinner than a strand of human hair. It’s a major step toward working with some of biology’s most delicate components.
Dylan Chiaro, graduate student and lead author of the study

A Collaborative Triumph

This research, originating from Mizzou’s College of Arts and science, unites the disciplines of biology, chemistry, physics, and space science. It holds the potential to revolutionize how scientists interact with the basic building blocks of life: molecules,proteins,and atoms.

Suchi Guha, a professor of physics and study co-author, played a crucial role in identifying the structure of the resulting material. Her lab employed surface-enhanced Raman scattering, a highly sensitive tool that analyzes how light interacts with molecules, to determine that the solid material exhibits properties similar to carbon fiber.

Post-processing analysis revealed that the purple membrane remained nearly unchanged,losing less than one nanometer in thickness. This demonstrates the ability to create patterns directly on fragile biological materials without causing damage, a challenge that has long perplexed scientists.

Bernadette Broderick, an assistant professor of chemistry and study co-author, contributed to the discovery of ketene, a short-lived chemical that forms during the electron beam process. King believes that Broderick’s lab’s expertise in astrochemistry can help elucidate how the ethanol ice transforms into a stable,solid material,which is a critical step in understanding the chemistry and physics underlying the method.

Each lab contributed a different piece of the puzzle. This kind of interdisciplinary teamwork is what really made the discovery possible.
Gavin King, professor of physics and study co-author