This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Scientists from Nanyang Technological University, Singapore (NTU Singapore) have developed a new class of light-activated compounds that could lead to safer and more versatile applications in 3D printing, cosmetics and medicine. These compounds, known as aryl diazirine photoinitiators, are used to solidify liquid resins into hard plastics with speed and precision using light.
The current industry-standard photoinitiators often face issues of toxicity and poor solubility in water. The NTU study, published in NPG Asia Materials, demonstrates that the new aryl diazirine photoinitiators are not only nontoxic to human cells but also offer superior performance, including reduced material shrinkage and compatibility with water-based sustainable resins. The paper is titled "Non-toxic aryl diazirine photoinitiators." Photoinitiators are a key ingredient in everything from the adhesives that seal electronics to the biocompatible hydrogels used in tissue engineering.
When exposed to light, they kick-start a chemical reaction called polymerization, which turns liquid materials solid in seconds. However, the most common photoinitiators, such as diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), have been identified as reproductive toxins, creating an urgent need for safer alternatives. In fact, both TPO and BAPO are being banned in some regions, such as the European Union (EU), due to health concerns.
The ban has disrupted the gel-nail sector, which relied on TPO for fast and reliable curing. The NTU team, led by Professor Terry W. Steele from the School of Materials Science and Engineering, found that aryl diazirines are a highly effective and biocompatible replacement.
Steele said, "The industry is facing a major challenge as the most effective and widely used photoinitiators are being regulated out of existence due to toxicity. Our goal was to develop a new 'activator' that is not only safe and biocompatible but also improves on the performance of existing materials. We have created a solution that addresses the toxicity problem head-on while opening new possibilities for innovation." One of the significant findings of the study is the new photoinitiators' ability to reduce the shrinkage that typically occurs when a liquid resin hardens.
The aryl diazirines release nitrogen gas during the curing process, a feature that can be tuned to counteract this contraction, leading to more stable and reliable finished products. Furthermore, several of these new compounds are soluble in water and liquid at room temperature. This behavior simplifies handling and allows them to be used in "greener" manufacturing and sensitive biomedical applications where organic solvents are avoided.
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