A pathological or injury-related narrowing of the windpipe or the main bronchi can end badly. Patients do not get enough air, are in danger of suffocating and often need medical help as quickly as possible. In order to correct such constrictions, surgeons insert tube-shaped implants, so-called stents, made of medically usable silicone or metal. Although these provide patients with rapid improvement, the implants have disadvantages: Metal stents have to be surgically removed with some effort, which places a new burden on patients. Silicone stents, on the other hand, migrate away from the insertion site. The reason for this is that the implants are not adapted to the patient's anatomy.
An ETH research team made up of members of the Complex Materials and Drug Formulation & Delivery groups, together with researchers from the University Hospital and the University of Zurich, has now developed an airway stent that is tailored to a patient and bioresorbable, i.e. it gradually degrades after implantation. These stents are manufactured using a 3D printing process and light-sensitive resins specially adapted for this purpose.
In the DLP process, a construction platform is immersed in a vat of resin. The platform is then exposed to UV light in the desired areas according to the digital model. Where the light hits the resin, it hardens. The platform is lowered a little and the next layer is exposed. In this way, the desired object is created layer by layer.
Until now, only rigid and brittle objects could be produced using DLP technology and biodegradable materials. The ETH researchers therefore developed a special resin that becomes elastic after exposure to light.
This resin is based on two different macro-monomers. The material properties of the object produced can be controlled by the length (molecular weight) of the monomers used and their mixing ratio, as the researchers show in their latest study in Science Advances.
As soon as UV light hits the resin, the monomers link together and form a polymer network. As the newly developed resin is too viscous at room temperature, the researchers had to process it at temperatures of 70 to 90 °C.
Source: ETH Zurich
