Medical Device
Material Selection
Material selection is a critical part of the product development cycle as it will directly impact the overall performance of the device as well as logistics, cost of goods, etc. Medical device can be especially challenging due to all the downstream testing that is often required. Also, switching materials is typically not an option once the material & device have been submitted to the FDA, so choosing the right material upfront is a key step in the process.
Our plastic engineering team at Plastikos has developed a list of questions and considerations to review when selecting your next material. Of course, our team is always open to schedule a DFM on your device should you need further input on material availability, limitations, processing, etc.
Medical Device Product Functionality
- What will the product be exposed to (Heat, Chemicals, Weather, etc)?
- Will the product be subjected to any type of stress or deflection?
- Will there be any type of secondary bonding operation?
- Is the product reusable?
- What (if any) sterilization method will be used on the device?
- Is optical clarity an important part of the product design?
- Will the product require a high gloss surface finish?
- Is there any secondary decorating or labeling required?
Material Logistics
- Is the desired material already purchased / in your supplier base today?
- Has a standard lead time for the material been determined?
- Does that lead time meet your project timeline?
- Has the raw material supplier communicated a minimum order quantity (MOQ)?
- Is the MOQ too large to justify given the expected annual volume of the part?
- Does the raw material supplier have or expect to have any allocation restrictions?
- Is the specified material a custom grade & does that impact the standard delivery and availability?
- Is there a suitable alternate grade of material that could be qualified?
- Is the specific material available in the country in which the product will be sold?
- And of course, what is the Cost / Pound, and will that meet your cost objectives?
Material Properties & Common Material Grades
| Less chemical resistance than semi-crystalline material. |
| Prone to stress cracking and fatigue. |
| Low shrink rate. |
| Better transparency than semi-crystalline. |
| Density not impacted by cooling rate. |
| Poor wear resistance. |
| ABS | – Housings – Household appliances |
| PC | – Optical applications – Medical devices |
| PSU | – Air & water treatment – Diagnostic Equipment, Re-Usable Devices, Sterilization |
| PPSU | – Hot water fittings / aerospace applications – Diagnostic Equipment, Re-Usable Devices, Sterilization |
| COC | – Optical applications – Medical devices |
| PEI | – Eye care products – Medical devices |
| Less prone to stress cracking/fatigue. |
| Higher shrink rate. |
| Typically, non-transparent. |
| Density directly impacted by cooling rate. |
| Good wear resistance. |
| Poor bonding with adhesives and solvents. |
| LCP | – Electronic connectors – Aerospace |
| HDPE | – Liquid containers – Food packaging |
| Nylon | – Automotive parts – Gears |
| PEEK | – High wear applications – High heat applications |
| PBT | – Miniature pumps – Electronic devices |
| Acetal | – Gears and bearings – Conveyor systems |
Material Analysis: Advantages & Disadvantages to Common Materials
| ABS | – Able to decorate – Medium impact resistance |
| PC | – High impact resistance – High heat resistance |
| PSU | – Good chemical resistance – Rigid / high strength material properties |
| PPSU | – Excellent chemical resistance / flame retardant properties – Excels in high heat & humidity environments |
| COC | – Excellent optical clarity – Considered “inert” used for many glass replacement products |
| PEI | – Long-term heat resistance – Good dimensional stability |
| ABS | – Flammable – Poor weather resistance |
| PC | – Poor scratch resistance – Requires additives if long-term UV exposure is required |
| PSU | – Difficult to process through hot runner systems – High mold temps required / sensitive to stress cracking |
| PPSU | – More expensive compared to its PSU alternative – Very high mold / processing temps required |
| COC | – High material costs |
| PEI | – High processing temperatures – High material costs |
| LCP | – Low viscosity for thin wall sections – High strength to weight ratio |
| HDPE | – High strength to density – Excellent chemical resistance |
| Nylon | – High wear resistance – Excellent abrasion resistance |
| Peek | – Abrasion resistant – Excellent chemical resistance |
| PBT | – Low moisture absorption – Good machining characteristics |
| Acetal | – Low friction for wear applications – Good dimensional stability |
| LCP | – Weak knit line strength – High material costs |
| HDPE | – Low strength and hardness – Cannot be imprinted without pretreatment |
| Nylon | – High moisture absorption – Requires UV stabilization |
| Peek | – High material costs – Extremely difficult to process |
| PBT | – Require UV stabilizers if used outdoors – Poor resistance to acid and bases |
| Acetal | – Not resistant to acids – Difficult to bond |
Material Analysis: Real World Applications
Microfluidic Device
The current part design contains an internal flange that is extremely prone to flash or no-fill due to the knife-edge condition that is created in the design. The current raw material is also rather shear sensitive, which adds to the issue if a no-fill is detected as a leak can occur.
Plastikos has experimented with alternative material grades that may provide a suitable replacement. After several material trials, we proved one to be highly effective to minimize the no-fill condition. This provided our client with increased shot-to-shot consistency and would eliminate the need for a secondary operation on their manufacturing line.
Medication Delivery Device
The current device is made from a high temperature, specialty resin, that cost upwards of $18/lb for the raw material. As volumes grew to tens-of-millions annually, our client was investing nearly $9 million annually into raw material alone for this device.
Today, we are in the process of qualifying a new resin with very similar material properties that will reduce the raw material cost by approximately 20%, thereby saving our client over $1.8 million in raw material cost, annually.
