Top Tips For Developing An Implantable Textile Solution
Dean King
Medical Textiles Programme Manager, Aran Biomedical
Textiles are a compelling solution for implantable medical devices, 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 straight forward as it may seem.
Here are my tops 10 tips for successful textile implant product development:
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. My advice would be to 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 facilitate 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. Choose Appropriate 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 fluids, such as vessel occlusion, filtration, blood flow diversion, or 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 attachment and tissue integration. In this instance, it is important to consider the appropriate balance in pore size to encourage the cell attachment 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. Choose the Optimum Fibre
Choosing the right fibre is essential for any textile design. The basic questions to ask are, what is the Denier or dTEX (i.e. the weight of the fibre) 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. Fibres can also be twisted prior to processing to provide additional strength; there are a number of new fibres on the market offering higher performance for implantable textiles. Ultimately the choice of fibre 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 optimisation.
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.
Here is a simple check sheet of design inputs to consider when benchmarking performance:
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 optimisation.
9. Optimise Your Textile Design
Post processing can deliver clear product differentiation, so it’s important to evaluate all the options. Here are a few things to consider:
- Shape setting – using laser cutting, a hot knife, or any cutting instruments, this process defines accurately the dimensional configuration for the implantable textile component parts.
- Heat Forming – this will ensure your implantable textile maintains its dimensional configuration. It can also form a textile into a 3D structure or a specific anatomical design or impart key performance criteria, such as stretch bias in a particular direction.
- Coating – There are numerous ways that coatings can provide a performance advantage to textile implants (e.g. an impermeable sealant, hydrophilic or hydrophobic coatings, adhesive layers, radiopaque markers, placement indicators etc.)
- Condensing – This reinforces the strength profile of the construct, offers a smooth feel, a lower coefficient of friction, as well as a lower profile.
- Component Integration – Integration of textiles with other components is often required to expand product functionality. Bonding, suturing or crimping, are typical means to integrate textile implants with other textile components, nitinol frames, needles, anchors and other implantable structures.
- Design Configuration – when it comes to textile design post processing, design can be elaborated by splicing loops or post processing multiple textile configurations into the one design, such as over-braiding.
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.