3D-printing the brain’s blood vessels with silicone could improve and personalize neurosurgery –new technique shows how

(THE CONVERSATION) – A new 3D-printing technique using silicone can make accurate models of the blood vessels in your brain, enabling neurosurgeons to train with more realistic simulations before they operate, according to our recently published research.

Many neurosurgeons practice each surgery before they get into the operating room based on models of what they know about the patient’s brain. But the current models neurosurgeons use for training don’t mimic real blood vessels well. These models lack essential structural details, give inaccurate tactile feedback, and sometimes exclude whole anatomical parts that will determine the procedure. Pre-surgery simulations that simulate the brains of patients could help reduce errors in real surgery.

However, 3D printing can make replicas that have the soft feel and the structural accuracy that surgeons need.

3D printing is often thought of as a process where layers of melted plastic are laid down and then solidify as a self-supporting structure or structure is constructed. Many soft materials don’t melt and re-solidify in the same way that 3D printers use plastic filament. Users only get one shot with soft materials like silicone – they have to be printed while in a liquid state and then irreversibly solidified.

3D Shaping Liquids

How can you create complex 3D shapes out of liquids without creating a puddle?

Researchers developed a broad approach called embedded 3D printing for this purpose. With this technique, the “ink” is deposited inside a bath of a second supporting material designed to flow around the printing nozzle and trap the ink in the place right after the nozzle moves away. By holding liquids in three-dimensional space, users can create complex shapes from them until they are solidified. Embedded 3D printing has been effective for structuring a variety of soft materials like hydrogels, microparticles and even living cells.

Printing with silicone is still a difficult task. While liquid silicone is an oil, most support materials are water-based. Oil and water have a high interfacial tension, which is the driving force behind why oil droplets take on circular shapes in water. This force can also cause 3D-printed silicone structures, even in support media, to deform.

These interfacial forces can cause small-diameter silicon features to become droplets while they are printed. A lot of research has gone into making silicone materials that can be printed without a support, but these heavy modifications also modify the properties that users care about, like how soft and stretchy the silicone is.

3D printing silicone with AMULIT

As researchers working at the interface of soft matter physics, mechanical engineering and materials science, we decided to tackle the problem of interfacial tension by developing a support material made from silicone oil.

We thought that silicone inks could be chemically very similar to our silicone supporting material. However, they would also be different enough to stay separated when 3D printed. There were many candidates for support materials that we tested, but the best was to create a dense silicone oil-water emulsion. It can be compared to crystal clear mayonnaise made from microdroplets of water and a continuum silicone oil. We call this method additive manufacturing at ultra-low interfacial tension, or AMULIT.

Our AMULIT support medium allowed us to print off-the shelf silicone at high resolution. We were able create features as small and as small as 8 micrometers (around 0.03 inches). The printed structures are just as durable and stretchy as traditional molded ones.

These capabilities enabled us to 3D-print accurate models of a patient’s brain blood vessels based on a 3D scan as well as a functioning heart valve model based on average human anatomy.

3D silicone printing for health care

Silicone is a critical component of innumerable products, from everyday consumer goods like cookware and toys to advanced technologies in the electronics, aerospace and health care industries.

Silicone products are usually made by injecting liquid silicone into molds and then removing it after solidification. Manufacturers are limited to producing products of a small number of predetermined sizes, shapes, and designs due to the difficulty and cost involved in manufacturing high-precision molds. Molding intricate structures requires the removal of delicate silicone structures without damage.

These challenges can be overcome and advanced silicone-based technology could be developed in the health care sector. Personalized implants or mimics of physiological structures may transform care.