3-D Printing of Brain’s blood vessels now possible-edited by Aishee Biswas

Recently published research shows that a new 3D-printing technique using silicone can create accurate models of blood vessels in the brain . This innovation enables neurosurgeons to train with more realistic simulations before operating, improving their surgical skills. Current models used for training lack important structural details and do not provide realistic tactile feedback. They often exclude anatomical components that are critical to performing the procedure. Realistic and personalized replicas of patient brains during pre-surgery simulations could minimize errors during actual surgical procedures.

 

The conventional 3D printing process involves laying down layers of melted plastic, resulting in a self-supporting structure. However, soft materials such as silicone do not re-solidify in the same way as plastic filaments. Therefore, users have to print soft materials like silicone while they are in a liquid state, and then they irreversibly solidify.

 

To make a brain-like structure and form from a 3-D printer, researchers have developed an innovative technique called  embedded 3D printing. The process involves depositing the "ink" within a bath of a second supporting material. The supporting material flows around the printing nozzle and traps the ink in place immediately after the nozzle moves away. This technique enables users to create intricate shapes from liquids, by trapping them in three-dimensional space until they solidify.
 

Embedded 3D printing has been successful in structuring a range of soft materials, including hydrogels, microparticles, and living cells. However, printing with silicone has been particularly challenging due to its oily consistency. Most support materials are water-based, and oil and water have a high interfacial tension. This force causes oil droplets to take on circular shapes in water, which also leads to deformation of 3D-printed silicone structures, even in a support medium.

 

In an effort to understand the significant reduction in interfacial tension and maintain separation for 3D printing, researchers experimented with several candidate support materials. Ultimately, they found that the most effective approach was to create a dense emulsion of silicone oil and water. This resulted in a crystal-clear mayonnaise-like substance composed of tightly packed microdroplets of water in a continuous stream of silicone oil. This process is known as additive manufacturing at ultra-low interfacial tension, or AMULIT.

 

Utilizing the AMULIT support medium, it became possible to 3D-print off-the-shelf silicone at high resolutions , achieving features as small as 8 micrometers in diameter (approximately 0.0003 inches). The printed structures exhibit the same stretchiness and durability as their traditionally molded counterparts.

 

Leveraging these capabilities, we successfully produced precise models of a patient's brain blood vessels using a 3D scan, as well as a fully functional heart valve model based on average human anatomy.

 

The versatility of silicone is evident in its widespread use across numerous industries. From everyday items such as cookware and toys to high-tech applications in electronics, aerospace, and healthcare, silicone plays a critical role.

 

Typically, silicone products are created by injecting or pouring liquid silicone into a mold and then removing the cast after solidification. However, the production of high-precision molds is expensive and challenging, limiting manufacturers to a predetermined range of product sizes, shapes, and designs. Additionally, removing delicate silicone structures from molds without damage poses an additional obstacle. The challenges increase when molding intricate structures, leading to manufacturing defects.

Overcoming these challenges could lead to the development of advanced silicone-based technologies in the healthcare industry. Personalized implants and patient-specific mimics of physiological structures could transform the delivery of care.