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Skin Irritation and Cytotoxicity Testing for Vapor Smoothed 3D Printed Personal Protective Equipment (PPE)

Above: GoProto 3D Printed Facemasks before (left) and after (right) being Vapor Smoothed.

As health and medical professionals across the globe struggle with the effects of the Covid-19 virus, health organizations, hospitals and first responders are encountering shortages of equipment and critical supplies needed to mitigate exposure by medical staff. In areas where the virus has spread slowly, lack of proper medical equipment could mean the risk of creating a new ‘hot zone’ where one did not exist. And in the case of locales already at the epicenter of the outbreak, the same shortage could literally mean the difference between life and death.

Additive manufacturing companies, including GoProto, have stepped up to fill the gaps in the current PPE shortage by offering quick turn and on demand parts using innovative design and a combination of technologies to produce equipment on par with standard PPE supplies. But on the mind of medical staff, and the healthcare supply procurement specialists, is the question of the safety of the materials and processes used to make them. With Vapor Smoothing, we can produce more water-resistant Nylon PA12 PPE equipment that has also proven to pass ISO certified skin irritation and cytotoxicity evaluations.

Above: GoProto Facemasks, 3D printed with MJF technology and vapor smoothed with Additive Manufacturing Technologies (AMT)’s PostPro3D® technology.

3D Printing & Personal Protective Equipment

For many in the trenches, this crisis brings with it the first time they have considered 3D printing for PPE. Adding to that concern is the impact on the health of medical staff in using newer technologies to manufacture PPE and the unique materials and or processes being used to achieve the final parts.

Certification of new materials and production methods for medical equipment has always been an exacting process – with good reason. And the process of vetting a new material or production method, or the repurposing of materials for new uses, has always been one that took months or years to conduct testing. Now, with the crisis in full bloom, many providers are looking for information that helps them understand the impact of issues such as skin irritation and possible cytotoxicity before using equipment.

Vapor Smoothing for Post-Processing

For GoProto’s standard PPE products, such as the Montana Mask, GoProto can use Additive Manufacturing Technologies (AMT)’s PostPro3D® technology to “vapor smooth” its MJF printed, Nylon PA12, parts. This results in not only reduced surface roughness, but improved toughness, and a significant decrease in surface water absorption. This technology smooths the surface of MJF 3D parts to achieve a quality comparable to injection molded parts. Data has shown that surface roughness (Ra) of PA12 parts can be taken from an as printed Ra of 6.15 µm down to an average surface roughness of 0.7µm.

Aesthetics aside, one big benefit of the vapor smoothing process is the significant reduction in surface water absorption. With as-printed MJF 3D printed parts, water tends to stick to the surface of the part, increasing the time it takes to fully dry after being exposed to moisture. In a critical and fast-moving crisis such as this, short drying times can speed reuse. Water absorption also increases the risk of bacterial or virologic matter interacting with the water remaining on the surface to create an unsanitary and dangerous condition. With Vapor Smoothing, water is deflected from the surface and does not penetrate over time compared to as-printed parts. For information on this and other test results, please reach out to GoProto directly for the detailed white paper on this study.

Above: Water absorption test results, as provided by Additive Manufacturing Technologies.

Skin Irritation

To test for skin irritation, several Nylon PA12 samples were printed using MJF technology, which were subsequently vapor smoothed using the AMT PostPro3D® technology. The standard for skin irritation is 15% or less cell vitality compared to a negative control. In the testing of these PA12 samples, cell vitality indicated only a 1.8% degradation, well within the limits required. Test material is considered “skin irritating” if it reduces cell vitality to less than 50% compared to the negative control. These tests were conducted using normative ISO references of ISO-10993-1 and ISO 10993-10 in a controlled environment by a testing lab.


To test for potential toxicity, several Nylon PA12 samples were printed using MJF technology, which were subsequently vapor smoothed using the AMT PostPro3D® technology. Using Triton x 100 as a toxic control substance and cell culture medium as a non-toxic control, the sample was incubated for 48hr under partial pressure in 5% carbon dioxide and then four samples were tested under four different levels of dilution to measure protein content.

The toxic media compared to the non-toxic control sample showed 6% protein in the test solution. Materials are considered cytotoxic if the extracted material results in a protein content of test cells equal to less than 70% when compared to the negative control. In the case of the PA12 sample using the vapor smoothed technology, the extracted material did not show a cytotoxic effect.

When evaluating medical devices, cytotoxicity is a key factor to measure because it can be done quickly in a simple lab test. It is a highly sensitive test that in this case showed that the sample in the cell culture media showed only 6% of protein content compared to the negative control. This means that the sample, and the face masks made using this process, are well within the valid acceptable range of ≤15% for medical devices.

About GoProto

GoProto is a rapid manufacturing company with customer service at the core of our corporate culture. We help manufacture parts for our product development customers in medical, aerospace, industrial, automotive, and many others. We utilize cutting edge technologies, methods, and the very best professionals to make 3D printing and conventional manufacturing fast, world class quality and great value.