Medical engineering often pushes the envelope of modern manufacturing capabilities. As such, advanced technologies are required to turn life-changing designs into consumer-ready products. One of these technologies is Carbon Digital Light Synthesis (DLS), which enables the production of parts made of engineering elastomers that vastly outperform competing materials in the stereolithography (SLA) or digital light processing (DLP) sphere. This article will explain the benefits of switching to carbon 3D printing in the medical industry.
Carbon DLS makes use of the CLIP process, which stands for Continuous Liquid Interface Production. CLIP consists of 2 steps as described below:
- Printing - Similarly to SLA printing, Carbon DLS makes use of a vat of liquid polymer and a light projection system to create solid parts. However, this is where the similarities end, Carbon DLS uses a special permeable screen that allows oxygen molecules through but keeps the resin in the reservoir. This oxygen creates a microscopic boundary layer at the screen/liquid interface known as the dead zone. This layer serves to prevent the resin from curing directly at the screen interface, allowing it to continuously flow into this dead zone and creating the isotropic properties unique to parts printed with Carbon DLS technology.
- Curing - Parts made from the more advanced materials on offer are not fully cured when they come out of the machine. They need to be thermally cured in an oven before they can reach their full mechanical potential. This heating helps accelerate crosslinking of the polymer chains, creating extremely tough and resilient parts.
Anisotropic vs Isotropic
To understand the benefits offered by carbon 3D printing in the medical industry, the difference between isotropic and anisotropic materials must be clarified.
- Anisotropic - Traditional 3D-printed parts are anisotropic in nature. This means that the part has different mechanical properties when measured in different directions. Take, for example, a part that is printed on an FDM machine; the part is built by adding layers on top of each other in the z-axis. These layer interfaces create weak points where cracks develop and failures ultimately occur. This means that parts are mechanically weaker when loaded in the z-axis as compared to their x or y-axes. Anisotropy is not an ideal material property when designing parts for the medical industry since these components often undergo complex loading scenarios that can occur in almost any direction.
Microscopic comparison of anisotropic and isotropic materials. Image Source: Carbon 3D
- Isotropic - Isotropic materials, on the other hand, have uniform properties when measured in any direction. A good example of anisotropic materials are metals like steel or aluminum. Their properties typically do not change regardless of which direction the forces are applied. This material behavior is critical in products that receive complex multi-directional loading. Very few printing processes can claim to create isotropic parts. However, the unique printing process of carbon DLS allows it to generate these critical isotropic materials.
What Materials are Available?
The carbon DLS process is unique in the sense that it can print elastomeric materials with rubber-like strength and resilience. Some of the key materials are listed below.
- UMA 90 (Urethane Methacrylate) - This material behaves similarly to standard SLA resin in the sense that it does not require post-print thermal curing.
- RPU 70 (Rigid Polyurethane) - This material is well-suited to production parts due to its strength, toughness, and heat resistance.
- FPU 50 (Flexible Polyurethane) - This flexible variant of the polyurethane range of resins adds additional toughness and fatigue resistance.
- DLS CE 221 (Cyanate Ester) - This rigid polymer has exceptional temperature resistance. Additionally, it has high strength and stiffness.
- DLS EPX 82 (Epoxy) - This rigid epoxy has excellent mechanical properties and is ideal for structural components.
- SIL 30 (Silicone) - This soft silicone urethane has impressive tear resistance and is biocompatible in terms of skin-contact applications.
- EPU 40 (Elastomeric Polyurethane) - This material is ideal for vibration damping and impact absorption.
The materials listed above cover a wide range of toughness, tensile strength, and abrasion resistance properties, ensuring that almost any application can benefit from one or more of them. All of these properties are ideal for medical applications where parts undergo high levels of cyclic loading or provide unmatched accuracy when used as guides or for surgical preparation. These applications are listed in more detail below.
Application #1 - Guides/Tools
Carbon DLS is capable of printing parts to help surgeons accurately locate drills or other surgical implements. The rapid production and low cost allow these guides to be custom printed based on 3D scans or MRIs taken of the patient so that each part is tailor-made to their physique. This allows for improved surgical accuracy and therefore reduced risk.
Application #2 - Surgical Preparation
Surgeons often prepare for complex surgeries by analyzing reams of data such as MRI or CT scans. Modern carbon 3D printing in the medical industry has more recently allowed surgeons to print full-scale representations of a patient's organs based on those scans. These models can then be used to help them prepare for complicated procedures.
Application #3 - Prosthetics
One of the most widely known uses of carbon 3D printing in the medical industry is the creation of cheap prosthetics. Prosthetics were typically high-cost items since they need to be custom made for each patient. Prosthetics printed using FDM or other layer-based printing techniques were usually not as mechanically strong as those made using cast molds. However, with carbon printing technology, prosthetics can be made from engineering-grade materials that have the strength and toughness to dramatically increase their performance.
Application #4 - Hearing Aids
Hearing aids are another medical technology that can benefit greatly from the flexibility offered by Carbon DLS printing. Hearing aids need to be matched perfectly to the shape of the patient's ear canal in order to function efficiently. As such, a high-resolution surface is required. DLS is capable of producing highly accurate prints that can comfortably fit in the patient's ear. Plus, more comfortable hearing aids and hearing protection devices can be made from softer elastomers that are only printable using carbon DLS technology.
Application #5 - Prototyping
Medical engineering relies on a rigorous research and development cycle. Oftentimes multiple prototypes need to be manufactured to test the form, fit, and functionality of a design. With carbon DLS it is possible to use cheaper, less advanced materials to manufacture the prototype and then simply switch out materials on the same machine to create consumer-ready products with minimal effort.
As the medical industry continues to generate advanced innovations, equally advanced manufacturing equipment is required to bring these innovations to market quickly and cheaply without compromising on quality and functionality. To learn more about how to leverage carbon 3D printing in the medical industry, make use of Xometry’s instant quote tool to get accurate cost estimates on your medical device.