By: Dean King, Medical Textiles Program Manager, Proxy Biomedical
Medical device engineers are increasingly gravitating towards biomedical textiles to aid in implant performance, primarily due to the versatility they offer in product design. Textiles can be developed in 2D and 3D implantable forms, with configurations limited only by the imagination. However, understanding the breadth of possibility in textile manufacturing and determining the optimum textile design isn’t as straightforward as it may seem.
Here are the tops tips to consider to fast-track your product development timeline:
1. Focus on Performance Not Process
It may seem obvious, but many product designers will consider a predicate device design and use this as the basis to determine whether they need either a woven, knitted or braided textile solution. Taking this approach will typically lead to a ‘me-too’ solution, without exploring the potential for substantial performance improvements. Keep an open mind regarding the manufacturing process, as there are numerous processing methods to obtain similar designs. The most important thing to do, at the outset, is determine the exact dimensional specifications, followed by the required functional performance of the device i.e. “what is it?” and “what does it need to do?”
2. Deliver Procedural Innovation
Product delivery will fundamentally impact product design, so when determining the basic criteria – “what is it?” and “what does it need to do?” – it is essential to understand “how will it get there”. It is also important to remember that effective product delivery can offer procedural innovation.
Transcatheter delivery creates dimensional limitations on implant size and makes the textile expansion profile integral to the design. Similarly during open surgery, the ability to place and secure the implant with ease is a distinct advantage. There are numerous textile solutions to facilitate this, such as improving how the textile unfurls to enable placement and designs that simplify or incorporate anchoring technology. Even the feel of the textile implant in the surgeon’s hands can play a role in successful procedural outcomes. Effective consideration of implant delivery and placement can play a critical role in product differentiation.
3. Determine the Pore Architecture
The pore size and structure of an implant plays an integral role in its performance in vivo. On the one hand pores control the flow of liquid, such as vessel occlusion, filtration and blood flow diversion, or facilitate seroma drainage during the healing process. In this instance the pore structure can range from blood impermeable to a macroporous design. On the other hand, pore size can be optimised to encourage cell adhesion and tissue integration. To achieve this it may be necessary to get the appropriate balance in pore size to encourage the cell adhesion without significant bacterial formation.
Finally the pore size, as well as its shape, directly effects the mechanical performance of an implant, so square, diamond or hexagonal pores, for example, will provide different directional elasticity or shape memory.
4. Source the Right Resin
Don’t underestimate the importance of choosing the right material. The raw ingredients of any design directly impact performance characteristics, such as: tensile strength, elasticity, resorption, durability, melt processing temperature, etc. Whether a device is planned for long term or short term implantation, it needs to be biocompatible and ideally have an established clinical history. It is important to remember that many traditional material suppliers no longer offer resins indicated for implantable use, so manufacturers need to source ‘Medical Grade’ resin that is not contra-indicated for medical implantation.
5. Choosing the Optimum Fiber
Choosing the right fiber is essential for any textile design. The basic questions to ask, include what is the dernier or dTEX (i.e. the weight of the fiber) and is it multi-filament or mono filament? Both of these criteria will impact device design and performance. At a simple level, multi-filament tends to offer better tensile strength than monofilament and may offer a more condensed textile structure, but on the other hand it can encourage greater bacterial formation. Fibers can also be twisted prior to processing to provide additional strength; there are a number of new fibers on the market offering higher performance for implantable textiles. Ultimately the choice of fiber will most likely be made on the basis of a range of performance criteria.
6. Rank Performance Criteria
In order to achieve the optimum balance of performance characteristics in a textile implant, it may be necessary to trade certain criteria, such as strength versus implant size, elasticity versus durability etc. Understanding which criteria have the greatest priority will help you during design optimization.
7. Benchmark Textile Performance
As mentioned, there are numerous textile processing methods to create your implantable design, but whichever processing method you choose, it is essential to benchmark performance against the key inputs.
8. Control Your Design
It’s important to remember that modern textile processing equipment has highly effective PC controls. This allows for excellent design details to be incorporated, while ensuring accuracy and consistency. Implantable textile designs can now integrate multiple design configurations seamlessly within the one structure and changing these key design inputs helps performance optimization.
9. Optimize Your Textile Design
Post processing can deliver clear product differentiation, so it’s important to evaluate all the options. Examples of factors to consider include shape setting, coating, component integration and design configuration, to name a few.
10. Design for Manufacture
As with any design process, it is essential to consider design for manufacturing. From a textile perspective this can include decisions around suturing versus bonding, hand sewing or machine sewing, integrated automated process steps or even custom designing machinery. Undertaking this process helps to ensure that the product achieves the right balance, in terms of design criteria, processing methods, and cost of manufacturing, making sure you get the product at the right price.