A new 3D printing technique using silicone can create accurate models of the blood vessels in your brain, allowing neurosurgeons to train with more realistic simulations before operating, according to our recently published research.
Many neurosurgeons practice each operation before entering the operating room based on models of what they know about the patient’s brain. But the current models that neurosurgeons use for training do not closely mimic real blood vessels. They provide unrealistic tactile feedback, miss small but important structural details, and often exclude entire anatomical components that determine how each procedure will be performed. Realistic and personalized replicas of patients’ brains during preoperative simulations can reduce errors in real surgical procedures.
However, 3D printing could create replicas with the soft feel and structural accuracy that surgeons need.
3D printing is usually thought of as a process of laying down layer upon layer of molten plastic that solidifies as a self-supporting structure is built. Unfortunately, many soft materials don’t melt and solidify like the plastic filament typically used by 3D printers. Users only get one shot with soft materials like silicone – they have to be imprinted in a liquid state and then irreversibly solidified.
Shaping liquids in 3D
How do you turn a liquid into a complex 3D shape without getting a puddle or a collapsing blob?
Researchers developed a broad approach called integrated 3D printing For this purpose. With this technique, the “ink” is deposited into a bath of a second backing material designed to flow around the print nozzle and collect the ink at the location immediately after the nozzle exits. This allows users to create complex shapes from liquids by holding them captive in three-dimensional space until it is time for the printed structure to solidify. Integrated 3D printing has been effective for structuring different soft fabrics such as hydrogels, microparticles and even living cells.
However, printing with silicone remains a challenge. Liquid silicone is an oil, while most support materials are water-based. Oil and water have a peak interface tension, which is the driving force why oil droplets take on round shapes in water. This force also causes 3D-printed silicone structures to deform, even in a supportive medium.
Even worse, these interfacial forces cause small diameter silicone features to break into droplets during printing. Much research has gone into making silicone materials that can be printed on without supportbut these heavy adjustments also change the properties that users care about, such as how soft and stretchy the silicone is.
3D printing silicone with AMULIT
As researchers working at the cutting edge of soft matter physics, mechanical engineering And material skillswe decided to tackle the problem of interfacial tension by using a supporting material made of silicone oil.
We reasoned that most silicone inks would be chemically similar to our silicone backing material, dramatically reducing interfacial tension, but also different enough to remain separate when compounded for 3D printing. We made many candidate support materials, but found that the best approach was to make a dense emulsion of silicone oil and water. You can think of it as crystal clear mayonnaise, made from packed micro droplets of water in a continuum of silicone oil. We call this method additive manufacturing at ultra-low interfacial tension, or AMULIT.
Using our AMULIT support medium, we were able to print high-resolution ready-to-use silicone, creating features as small as 8 microns (approximately 0.0003 inches) in diameter. The printed structures are as stretchy and durable as their traditionally shaped counterparts.
These capabilities allowed us to 3D print accurate models of a patient’s cerebral blood vessels based on a 3D scan, as well as a functioning heart valve model based on average human anatomy.
3D silicone printing in healthcare
Silicone is one crucial part of countless productsfrom everyday consumer goods such as cookware and toys to advanced technologies in the electronics, aerospace and healthcare industries.
Silicone products are usually made by pouring or injecting liquid silicone into a mold and removing the mold after solidification. The cost and difficulty of manufacturing high precision dies limits manufacturers to products with only a few predetermined sizes, shapes and designs. Removing delicate silicone structures from molds without damage is an additional barrier, and manufacturing defects increase when molding highly intricate structures.
Overcoming these challenges could enable the development of advanced silicone-based technologies in healthcare, where personalized implants or patient-specific mimics of physiological structures could transform care.