Neurosurgeons often practice surgeries prior to the actual procedure using patient brain models, but current models lack realism in replicating blood vessels and providing accurate tactile feedback. Additionally, they may not include crucial anatomical structures that affect the surgery. To improve accuracy and reduce errors during actual surgeries, personalized 3D printed replicas of patient brains could be used, as they can replicate the soft texture and structural details needed for effective pre-surgery preparation.

Scientists at the University of Florida (Gainesville, FL, USA) have developed a new 3D printing method using silicone that can create accurate models of blood vessels in the brain, providing neurosurgeons with more realistic simulations for pre-surgical preparation. While embedded 3D printing has been successful for creating various soft materials, such as hydrogels, microparticles, and living cells, printing with silicone has been challenging. Due to the high interfacial tension between oil (which liquid silicone is) and water-based support materials, 3D-printed silicone structures have been prone to deform and small-diameter features break into droplets during the printing process.

Numerous studies have been conducted to produce silicone materials that can be printed without the need for support. However, altering the properties of silicone to achieve this also affects the material's softness and stretchiness, which are significant considerations for users. To address the issue of interfacial tension, researchers from the fields of soft matter physics, mechanical engineering, and materials science have developed a support material using silicone oil. The team hypothesized that most silicone inks would share chemical similarities with their silicone support material, thereby significantly reducing interfacial tension while remaining distinct enough to be printed separately in 3D.

The team of researchers tested various support materials but determined that the most effective solution was to create a dense emulsion of silicone oil and water that resembled a crystal clear mayonnaise, made from packed microdroplets of water in a continuum of silicone oil. The researchers coined the term "additive manufacturing at ultra-low interfacial tension" (AMULIT) for this method. Using the AMULIT support material, the researchers managed to print off-the-shelf silicone at high resolution, producing features as small as 8 micrometers (approximately 0.0003 inches) in diameter. The printed structures were equally durable and stretchy as those produced through traditional molding. This breakthrough allowed the team to create precise 3D models of a patient’s brain blood vessels based on a 3D scan and a functioning heart valve model based on average human anatomy. 

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