Medical textiles use both natural and synthetic fibres. The various products available in this category are sutures, orthopaedic implants, cardiovascular implants, soft - tissue implants, bandages, artificial body parts, surgical clothing, wiper, incontinence diapers etc. The hygiene products have immense market potential. However, the low level of awareness is a major constraint. Medical textiles were developed when medicinal and textile scientists joined hands to work for application, which are dear to mankind. The medical textile industry has diversified with new products and innovative designs. It involved polymer technology, which yielded a wide range of applications in medical field. Depending upon the nature of the application, many textile products are disposable, and made out of nonwoven fabrics.

 

Performance of medical textiles

Textile materials for medical applications typically have specific performance requirements relating to strength, stiffness, abrasion resistance, and mechanical potency. Different types of fabrics are employed in medical textiles.

 

• Woven fabrics are usually dimensionally very stable but less extensible and porous than the other structures. One disadvantage of wovens is their tendency to unravel at the edges when cut squarely or obliquely for implantation. However, the stitching technique known as a Leno weave - in which two warp threads twist around a weft - can substantially alleviate this fraying or unraveling.

• Weft-knitted structures are highly extensible when compared with woven fabrics. However, they are also dimensionally unstable unless additional yarns are used to interlock the loops and reduce the extension while increasing elastic recovery. Warp-knitted structures are extremely versatile, and can be engineered with a variety of mechanical properties matching those of woven fabrics. The major advantage of knitted materials is their flexibility and inherent ability to resist unraveling when cut. A potential limitation of knitted fabrics is their high porosity, which - unlike that of woven fabrics - cannot be reduced below a certain value determined by the construction.

• Braided structures are typically employed in cords and sutures. These can be designed using several patterns, either with or without a core. Because the yarns criss-cross each other, braided materials are usually porous and may imbibe fluids within the interstitial spaces between yarns or filaments. To reduce their capillarity, braided materials are often treated with a biodegradable (poly-lactic acid) or non-biodegradable (Teflon) coating. Such coatings also serve to reduce chatter or noise during body movement, improve hand or feel, and help position suture knots that must be transported by pressure from a surgeon's finger from outside the body to the wound itself.

• Nonwovens are finding good numbers applications in medical textiles. The properties of nonwovens are determined by the constituent polymers or fibres and by the bonding process. For instance, expanded PTFE products can be formed to meet varying porosity requirements. Because of the expanded nature of their microstructure, these materials compress easily and then expand - a suture, for example, can expand to fill the needle hole made in a tissue - allowing for tissue in growth for applications such as arterial and patch grafts. Polyurethane-based nonwovens produce a product that resembles collagenous material in both structural and mechanical properties, particularly compliance (extension per unit pressure or stress). The porosity of both PTFE and polyurethane-derived nonwovens can be effectively manipulated through control of the manufacturing processes.

Conclusions

Medical textiles find lot of opportunities in numerous applications. There are general uses such as bed linen, and surgical dressing materials, which are of traditional nature. The developments in medical textiles have led to highly critical function oriented application making the field important and vibrant from the point of view of market and product development.

About the Authors:

G S Nadiger and P S Ghosh are associated with Textiles Committee, Ministry of Textiles, Govt of India, Mumbai.