Authors: Xianbo Hu, Emmett McArdle

Avery Dennison Medical’s R&D managers Emmett McArdle and Xianbo Hu discussed the quadruple bonding capabilities required by medical device developers and healthcare providers—and why providing the right combination is so challenging.

For many medical equipment professionals, the challenge of meeting the needs of the multi-faceted healthcare market is like modern people’s pursuit of the Holy Grail.

For medical adhesives, this is certainly true. As one of the basic building blocks of medical equipment such as wound care dressings and wearable devices, these materials must have different properties. Here is a brief introduction to four popular adhesive qualities.

Repositionability is an important quality of some medical devices. For example, a healthcare provider may need to lift the dressing to examine the wound, then adjust and re-fix it. Or the nurse may want to remove the self-adhesive N95 respirator during work breaks and then put it on and return to work. Soft silicone adhesives (SSA) are ideal for low-viscosity applications such as advanced wound dressings. SSA maintains its adhesive properties during repositioning. They do not remove skin cells during the removal process. If the opposite happens and the skin cells are pulled apart, they will mask the adhesive and affect its ability to reattach. Other repositionable options include soft acrylic adhesives. Equipment designers may use acrylic in applications that require repositionability, greater grip, longer wear time, one-time use, or lower unit cost.

For medical equipment that must maintain a relatively heavy weight or remain safe for a long time under harsh conditions, it must have strong grip and adhesion. For example, superabsorbent wound dressings contain large amounts of liquid between changes. Some wearable devices must remain firmly connected through showers, exercise, and other daily activities. Nevertheless, the grip of the adhesive should never cause skin trauma, especially since it will be reused around the same body part in many cases. Rubber-based adhesives provide strong grip, but are not breathable and tend to be too aggressive for delicate skin.

It is important to consider the entire range of adhesives related to the desired end use. Adhesives can be designed to have different viscosity levels, and different carrier materials can be utilized. For example, acrylic adhesives can be coated in a breathable, soft carrier material to improve comfort while providing strong retention. In addition, SSA can be designed to have high viscosity. This SSA may be very suitable for some superabsorbent dressings, but its higher degree of peel adhesion may affect non-traumatic or painless release. However, high-viscosity SSA may be suitable for wearable devices with medium wear time. In this application, the patient's skin may not be as susceptible to trauma as the skin of a severely injured patient.

Gentle wear and no damage removal

The demand for adhesives that provide gentle abrasion and damage-free removal is growing. These qualities are essential for the wound care of the elderly, infants and other people with fragile and delicate skin. In addition to gentle adhesion, health care providers often need to reposition when treating severe or chronic skin injuries so that they can temporarily remove the dressing to inspect the wound, or change its position so that the clean part of the dressing faces the wound and is ready Absorb liquid and exudate. Gentle dressings must generally provide a hydrophobic barrier around the wound to keep fluids away from the wound and the area around the wound. This helps prevent maceration and wound enlargement. All along, dressings should be comfortable for the patient, and every time the dressing is repositioned or removed, there should be minimal or no discomfort. Here, SSA is once again the preferred adhesive choice because they provide the most important properties required for optimal healing and patient experience.

Extending wearing time is one of the most challenging performance requirements facing medical device developers today. For example, some wearable devices now require 30 days of wear time, while previous applications may have stopped for 5, 10, or 14 days. As the wear time increases, adhesives are needed to withstand many environmental stresses, from daily showers to exercise. Whether it is cycling, hiking, swimming or any number of activities, patients want and need to maintain an active lifestyle, and their medical equipment is expected to keep up. At the adhesive level, this means providing the right combination of sustained grip, breathability and water resistance. Acrylic pressure sensitive adhesives (PSA) can be designed to have strong retention, water resistance and breathability. When PSA is coated on a highly breathable carrier material, the quality of the latter is closely related to comfort.

Next time the adhesive requirements of your product seem to be quite demanding, remember that you can work with your material supplier to find practical and innovative solutions.

Authors: Xianbo Hu, Emmett McArdle

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