From Copper Pots to Smart Sterilizers: A Century of Humanity's Battle Against Microbes

In an exhibition case at the Tsinghua University Museum of Science, a high-pressure steam sterilizer made of copper stands quietly, its mottled surface etched with the marks of time. Born in the 1940s, this instrument once served as the "heart" of the microbiology laboratory at the School of Environment, witnessing the journey of modern sterilization technology in China from its introduction to widespread adoption.

Its presence is not merely the physical survival of a scientific tool, but a historical footnote to humanity's博弈 with microbes and the symbiosis of science and technology. From the empirical disinfection practices of ancient times to the precise control of modern intelligent sterilization equipment, every breakthrough in sterilization technology has rewritten the narrative of humanity's fight against infection and exploration of the microscopic world.

01

Germination and Exploration: The Awakening from Empirical Disinfection to Scientific Sterilization

In the era before microbiology was born, human understanding of infection remained at an empirical level. Ancient Greek physicians used cauterization to treat wounds; China's Ming Dynasty "Compendium of Materia Medica" recorded "steaming the clothing of the sick to prevent contagion." These simple disinfection methods essentially utilized high temperatures to destroy the living environment of microorganisms.

In 1679, French inventor Denis Papin's "Digester" emerged, a device that used steam pressure to raise the boiling point of water, linking temperature to sterilization effect for the first time, becoming the prototype of the pressure sterilizer. Papin likely never imagined that this utensil, intended for rapid cooking, would become a "sterilization marvel" in laboratories a century later.

The 19th century was the golden age of microbiology. The research of Pasteur and Koch completely unveiled the mystery of microbes. In 1879, based on Papin's principle, Pasteur's team invented the first modern high-pressure steam sterilizer, the "Autoclave." This device raised the steam temperature to 120°C within a sealed chamber, achieving for the first time the efficient killing of bacterial spores – the most resilient microbial structures in nature, which had rendered boiling disinfection ineffective.

Simultaneously, Koch's proposed "non-pressure steam sterilization method" demonstrated the diverse paths of scientific exploration: by using fractional heating to kill microorganisms in culture media, he avoided the destruction of nutrients by high temperatures. This pursuit of a "balance between safety and effectiveness" provided ideas for sterilization needs in different scenarios.

02

Technological Iteration: From Laboratory Marvel to the Establishment of Industrial Standards

In the early 20th century, with the advent of the electrical age, sterilization equipment underwent mechanization and standardization. The "Ellipse autoclave" launched by the Bramhall Company in 1913, with its double-door design, precisely controlled air pressure, solving the problem of air retention in the sterilization chamber and greatly improving steam penetration efficiency. This technological breakthrough quickly moved from the laboratory to the medical field. By the 1930s, high-pressure sterilizers were commonly equipped in American hospitals, and the surgical infection rate dropped by 70% compared to the beginning of the century.

In the East, the spread of sterilization technology progressed alongside the establishment of China's modern scientific research system. In 1948, Professor Tao Baojie of Tsinghua University brought back a high-pressure steam sterilizer from the United States, which became a rare and crucial scientific tool in China at that time. In the laboratory of the Civil Engineering Department at Tsinghua University after its post-war reopening in Beiping, this copper sterilizer undertook the core tasks of microbiological experiments: culture media taken from the incubator needed its sterilization before inoculation; experimental glassware required its high-temperature treatment to avoid contamination.

Professor Jiang Zhanpeng of the School of Environment recalled that in an era of material scarcity, this instrument, paired with a 20°C incubator, formed the "golden duo" of the laboratory, supporting the earliest research on water supply and drainage microbiology in New China and laying the foundation for the subsequent development of water pollution control technology. It remained in service until the 1990s, when it was retired due to a leaking lid, having served for over 40 years and witnessed the exploratory journey of three generations of researchers.

03

Diversified Development: From Single High-Temperature to All-Scenario Sterilization Solutions

In the latter half of the 20th century, sterilization technology exhibited trends of specialization and intelligence. The medical field spurred the development of rapid sterilization cycles, compressing sterilization time to 15 minutes using pre-vacuum technology to meet the immediate needs of emergency instruments. The pharmaceutical industry developed double-door sterilizers, combined with vacuum drying technology to ensure drugs remained uncontaminated. In laboratory settings, sterilization baskets and fixtures for different materials emerged, solving the sterilization challenges of precision instruments.

The core of these improvements was the balance between "sterilization efficiency and object protection" – for example, enzyme-containing reagents require low-temperature formaldehyde sterilization, while metal instruments are suitable for high-temperature steam. Behind this technological differentiation lies a deep understanding of microbial characteristics.

The rise of low-temperature sterilization technology marked the field's shift from "high-temperature dependence" to "precision adaptation." The invention of the ethylene oxide sterilizer in 1949 achieved efficient sterilization at room temperature for the first time, protecting heat-sensitive materials like plastics and electronics. The advent of hydrogen peroxide plasma sterilizers in the 1990s shortened sterilization time to 30 minutes without chemical residues, making them the preferred choice for delicate instruments like endoscopes. These technologies complement traditional high-pressure steam sterilization, building a comprehensive sterilization system covering healthcare, food, pharmaceuticals, and scientific research.

04

Scientific Principles: The Microbiological Code and Industry Consensus Behind 121°C

Why is 121°C considered the "golden temperature" for sterilization? The establishment of this standard is both an inevitable choice based on microbiological principles and a result of industrial-era standardization. The core component of bacterial spores, calcium dipicolinate, undergoes irreversible decomposition at 121°C, causing the spores to lose their ability to revive. Simultaneously, saturated steam pressure at 15 psi (103 kPa)恰好 raises the boiling point of water to this temperature. This parameter places moderate demands on equipment materials, balancing sterilization effectiveness with manufacturing costs.

From a historical perspective, the普及 of pressure gauges and temperature sensors in the late 19th century made precise control possible. 121°C gradually transformed from laboratory experience into an industry standard, incorporated into various national pharmacopoeias and ISO standards.

The "precision" of modern sterilization technology is further reflected in the全程 management of microbial control. "Sterilization validation" in pharmaceutical production requires monitoring temperature distribution, sterilization time, and microbial load, verifying sterilization effectiveness through biological indicators (e.g., Geobacillus stearothermophilusspores). Hospital central sterile supply departments introduce tracking systems to record the sterilization parameters of each batch of instruments in real-time, ensuring traceability. These measures transform sterilization from an "empirical operation" to a "data-driven" process, increasing the success rate of infection control to 99.999%.

05

A Mark of Civilization: The Scientific Spirit and the Community with a Shared Future for Humankind Behind the Sterilizer

Tsinghua University's sterilizer, becoming a museum piece in 2018, completed its transformation from a "practical tool" to a "cultural symbol." Its story connects the hardships and奋进 of the beginning of China's modern scientific research: in the aftermath of the War of Resistance Against Japan, amidst widespread devastation, scholars like Tao Baojie used limited funds to introduce关键 equipment, setting up microbiological research platforms under简陋 conditions. During the technological catch-up after the reform and opening-up, researchers, relying on these "old partners," cultivated generation after generation of environmental engineering talent, propelling China's sterilization technology from introduction and absorption to independent innovation.

From a broader perspective, the evolution of sterilization technology is the evolutionary history of humanity's博弈 with microbes. When high-pressure steam sterilizers eliminate pathogens in laboratories, when low-temperature plasma devices protect delicate instruments, when ultraviolet disinfection lamps purify the air, these technologies collectively weave an "aseptic network" that safeguards human health.

As Pasteur said, "Chance favors the prepared mind." Every breakthrough in sterilization technology stems from the reverence for and exploration of natural laws – Papin's steam principle, Pasteur's discovery of microbes, the intelligent control of modern engineers – all are the best footnotes to the concept of "Tools Embodying Principles" (器以载道).

Epilogue

When we gaze at the high-pressure steam sterilizer in the exhibition case, we see not just an old instrument, but a scientific silhouette of an era. It once billowed steam on the bench in the Tsinghua laboratory, rotated valves beside the laminar flow hood, was gently mentioned in the acknowledgments of research papers, and finally became a文明 footnote under the museum lights. The century-long变迁 of sterilization technology tells the story of how humanity moved from ignorance to rationality, from experience to science, from single technological breakthroughs to systematic solutions.

Today, as biosafety becomes a global issue, the importance of sterilization technology becomes increasingly prominent. During the COVID-19 pandemic, high-pressure steam sterilizers operated 24/7 to process medical waste, and low-temperature sterilization equipment ensured vaccine production safety. These "silent guardians" continue to play a key role on the invisible battlefield.

Tsinghua University's sterilizer may no longer emit the roar of steam, but the scientific spirit it carries – the pursuit of precision, the exploration of the unknown, the reverence for life – rises eternally like steam, inspiring a new generation of researchers to continue writing more legends of "Tools Embodying Principles" in the intertwining of the microscopic world and macroscopic civilization.