Fukuoka, Japan—In rapidly aging societies like Japan, the simple act of swallowing meals can be challenging for many. This condition, known as dysphagia, affects millions of people worldwide and can significantly deteriorate a person's quality of life. While texture-modified foods like purées can make swallowing safer, it is difficult to tailor these foods to the wide spectrum of dysphagia, as some individuals can tolerate more solid meals while others require much softer textures. Publishing in the journal Scientific Reports , research teams from Kyushu University and Cardiff University have developed a new 3D bioprinting method that can customize the texture, adhesiveness, and water retention of protein-based emulsion gels for dysphagia diets using controlled radiofrequency (RF) and microwave (MW) energy.
"For many people with dysphagia, meals are often limited to jelly-like materials, which can diminish the enjoyment of eating," explains Shuntaro Tsubaki , first author and Associate Professor at Kyushu University's Faculty of Agriculture . "Our goal is to create meals that are not only safe but also appealing."
Tsubaki saw an opportunity to apply his expertise in microwave engineering to solve this challenge. "Conventional heating methods heat everything inside indiscriminately—both the parts you want to react and the parts you don't," he elaborates. "Microwaves are different. They can be controlled to heat only specific materials selectively. This precision is the key."
The team first developed a bioink that is composed of two main compounds: a stable oil-in-water emulsion and an aqueous solution containing egg white protein and stabilizers. These are then combined with a small amount of magnesium chloride, which acts as a microwave absorption aid, helping the bioink to heat efficiently and promoting the protein denaturation necessary for the liquid to solidify into a gel. To print this bioink, the team constructed a custom 3D bioprinter using Lego Mindstorms EV3 inspired by previous research from their Cardiff University collaborators.
"After our initial tests proved we could control the gel's texture with different energy frequencies, we then loaded the bioink into the 3D printer and extruded it through a thin applicator," explains Tsubaki. "As the bioink passes through the applicator, we apply a controlled burst of RF or MW energy to it, turning the bioink into a gel. That gel is deposited onto the printing dish layer by layer as the bioprinter nozzle moves across the dish."
The team's experiments demonstrated that by simply changing the frequency of the energy applied, they could produce gels with a range of properties suitable for different dysphagia diet requirements. When they used a lower frequency of 200 MHz, which falls in the radiofrequency range, the resulting gel was significantly harder and held its structure and water content more effectively. In contrast, using a higher frequency of 2.45 GHz, similar to that of a standard kitchen microwave, produced a gel that was much softer and more adhesive.
"The important thing is that we can control the texture by frequency, creating a customized texture for each person's needs," concludes Tsubaki. "Our new method holds potential beyond dysphagia diets—extending to artificial meat, functional nutrition, medical food, and even space rations. We are already working on other edible materials that can be 3D bioprinted. The ability to regulate protein aggregation and even trap flavors inside the oil phase could also lead to flavor-enhanced food-tech products."
