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Hydrogels and MRI: meet three biomedical engineers reshaping health care
Sandy Ong is a freelance writer based in Singapore.
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Anna Napolitano is a freelance journalist in London.
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Biomedical engineering encompasses a broad range of research with clinical applications, from creating surgical implants to using physics to improve medical imaging. Here we focus on three researchers whose fundamental work is paving the way for such health-care solutions.
Hydrogels are among a biomedical engineer’s most favoured materials, thanks to their water-rich, highly porous and elastic nature being able to closely mimic human tissue. But they face some key limitations, says Xinyu Dong: “They’re often quite fragile and their high water content makes them sensitive to dehydration and freezing when surrounding conditions change.”
Dong, a materials scientist at the National University of Singapore (NUS), creates next-generation, high-performance hydrogels using freeze casting, a technique normally used to make ceramic scaffolds that are used as 3D templates to guide bone repair. Also known as ice templating, freeze casting involves mixing a material with water to form a slurry, placing it in a mould, and then using a temperature gradient to grow ice crystals in a particular direction. This forces the slurry’s particles into the spaces between the crystals so that, after evaporating the ice, “what’s left behind is an organized network of pores” in the desired material, explains Dong.
Dong began experimenting with freeze casting in 2020 during her PhD at NUS, creating porous ceramic scaffolds that mimic the structure of bone: strong, yet able to deform to a degree without breaking1. She later applied this to aerogels — ultra-lightweight materials composed mostly of air — and hydrogels. “These materials are very different,” says Dong. “But the basic idea is the same: by controlling their structure at different scales, we can change how they behave and give them useful properties.”
In 2024, Dong proposed a twist on freeze casting2: instead of evaporating the ice after freezing, the mould is removed and soaked in a chilled organic solvent. As the ice gradually dissolves into the solvent and the organic liquid takes its place in the channels throughout the newly formed gel, the polymer walls are pulled closer together, increasing the linkages between them. The solvent also incorporates salt ions into the matrix, which makes the material electrically conductive. The result? Tougher, stronger and more stretchable skin-like organohydrogels — ideal for use in wearable electronics and soft robotics.
Dong and her collaborators described one such application this year in Nature Communications3, using an extension of this technique. “We developed a soft hydrogel-based electronic skin that formed close and stable contact with the body,” she says. When integrated into a wristband, the gel could be used to monitor skin temperature, pulse and sweat concentration.