Glass, with its fascinating properties and versatility, has captivated human beings for centuries. From ancient times to the modern era, this extraordinary substance has been used in a myriad of applications, ranging from delicate smartphone screens to crucial vials holding life-saving vaccines. As materials scientists devoted to studying glass, we constantly strive to deepen our understanding of this unique material and explore its untapped potential for future innovations.
But what exactly is glass?
To comprehend glass, it is essential to grasp its manufacturing process. The journey begins by heating a mixture of minerals, often comprising soda ash, limestone, and quartz sand, to an astonishing temperature of approximately 2,700 degrees Fahrenheit (1,480 Celsius). This intense heat causes the minerals to melt into a liquid state, where they exhibit free-flowing and disordered movement. Upon rapid cooling, instead of crystallizing like most solids, the mixture solidifies while preserving its disordered structure. It is this atomically disordered arrangement that defines glass.
On short timescales, glass behaves like a solid. However, its liquid-like structure means that over an extended period, glass undergoes a gradual process known as relaxation. During relaxation, the atoms within a glass structure slowly rearrange themselves into a more stable configuration. Remarkably, even after 1 billion years, a typical piece of glass will undergo a minuscule change in shape, measuring less than 1 nanometer—a mere 1/70,000th the diameter of a human hair. Consequently, the common belief that old windows thicken at the bottom due to centuries of gravity-induced flow is unfounded.
When we colloquially refer to glass, we often envision a hard, transparent substance made from fused sand, soda, and lime. However, glass can manifest in various forms, not limited to transparency, and can be produced from diverse combinations of elements, as long as the liquid mixture can be cooled rapidly enough to prevent crystallization.
Glass: An Ancient and Modern Companion
Humanity’s relationship with glass spans over 4,000 years, with early utilization focusing on decorative glass beads and arrowheads. Archaeologists have unearthed evidence of glass workshops dating back 2,000 years, such as the one near Haifa, Israel, dating back to around 350 C.E. These archaeological sites have revealed fragments of raw glass, glass-melting furnaces, utilitarian glass vessels, and remnants from glass-blowing practices.
The advent of modern glass manufacturing occurred in the early 20th century, accompanied by the development of mass production techniques for glass bottles and flat glass sheets. Glass subsequently became indispensable to the electronics and telecommunications industry, eventually forming the backbone of the internet.
Unleashing the Potential of Glass
In the present day, scientists are pushing the boundaries of glass applications far beyond conventional use. The forefront of glass research focuses on manipulating its complex atomic structure and relaxation process to achieve specific properties.
Due to its inherent atomic disorder and perpetual transformation, every point on a piece of glass possesses slightly different characteristics—be it strength, color, conductivity, or other attributes. Consequently, two seemingly similar glass pieces, manufactured with identical materials and processes, may exhibit distinct behaviors.
To enhance our ability to predict and control glass behavior, our research team has been dedicated to quantifying and manipulating the ever-changing atomic structure of glass. Recent advancements in this field have yielded tangible benefits to existing technologies.
For instance, thanks to innovative processing techniques, phone screens are now more resistant to cracks compared to those from 2014. By minimizing variations in atomic bond strengths, researchers have made it more challenging for cracks to propagate. Furthermore, internet speeds have significantly improved over the past two decades due to the development of techniques that enhance the density uniformity of glass used in optical fibers.
