How Adhesive Selection and Proper Material Fabrication Improve Product Quality and Patient Satisfaction
Wearable patch pumps and other “mechanized” drug delivery devices are often confused with less-sophisticated transdermal patches that are used to deliver drugs through the skin and into the bloodstream over a short period of time. Patch pumps are used primarily for insulin therapy, though use for drug delivery is being explored by other large molecule drug manufacturers. Patients typically wear these devices for several weeks, even months, based upon the severity of their medical needs.
The Centers for Disease Control (CDC) estimate that there are nearly 19 million people with diagnosed diabetes, and another 7 million undiagnosed cases. With incidence rates climbing, medical device manufacturers are seeking solutions to help diabetes patients live active lives, especially for the millions of young people affected by the disease.
Elements in Patch Pump Designs
A patch pump is composed of a small, reusable pump that contains a reservoir of insulin, or other drug, a small needle on the side facing the patient, electronics, on-board controllers, and a human interface containing buttons or small screens, all covered in a plastic case. The pump is attached to an adhesive patch that is worn until the patient needs to change it. Unfortunately, a common complaint among users is that the patch loses its adherence, especially when they sweat or bathe.
The constant re-positioning of the patches can cause irritation and potentially infection, especially if the adhesive is too aggressive.
In order to design patch pumps that adhere for long periods of time on a range of skin conditions, medical device manufacturers require the right match of adhesive and material for the application. There needs to be a balance between the need for a strong bond to hold the bandage or device in place for as long as the treatment requires, and the ability to remove or reposition it without causing unnecessary irritation or skin trauma, such as skin tears or stripping.
The Role of Advanced Adhesives in Wearable Patch Pumps
Selection of the correct adhesive for a wearable patch pump is critical as patients may wear these devices for several days before replacing them. Important factors that must be considered include skin type, age, ethnicity, how often the dressing is changed, exposure to fluids, physical activity, and more. The right adhesive will need to accommodate a person’s body movements that occur during normal wear as well as when the person showers or sweats from exercise. This is an important point as wearable patch pumps are intended to free patients from being connected to traditional insulin pumps which inhibit some normal activities.
Advanced adhesives are being created to improve stretchability, conformability, breathability, absorbency, porosity, and durability. New classes of adhesives with custom formulations include hydrocolloid, hydrophilic, and conductive adhesives which provide kinder, gentler adherence to skin with long lasting bonds for extended wear, and in some cases, the ability to withstand or absorb fluids. They have the following general properties:
- Adhesion to organic and inorganic surfaces
- 100% solid before and after curing
- Optimized for wetting and gap filling
- Working characteristics suitable for
- Compatibility with different forms
- Anti-microbial characteristics
Hydrocolloid adhesives are the most “skin-friendly” solution and are body fluid resistant. They represent a special type of pressure-sensitive adhesive with both fast adhering characteristics as well as fluid absorbency and can also be formulated for extended wear.
In order to attain greater skin adhesion beyond one to two days, it is necessary for the adhesive to absorb fluid. Absorption effectively manages skin perspiration. Without this ability, the adhesive would fail in a very short period of time and the skin would be irritated. However, absorption can also cause adhesive degradation – the key is limiting absorption to the minimum necessary to manage perspiration.
Suppliers creating medical grade adhesives have developed high-tack, high-shear formulations with improved abilities to maintain adhesion after exposure to fluids. Hydrocolloid adhesives can be applied to many substrate materials, including polyethylene foam, PVC foam, and polyurethane foam or film. Hydrocolloid tapes are available as single- or double-coated tapes. Double-coated tapes can have a hydrocolloid adhesive on one side to stick to skin, and an industrial strength adhesive on the other to adhere to another device, such as a wearable patch pump. Since hydrocolloid tapes are custom formulations and applications, working with an adhesive and material expert is critical to achieve the exact formulation and combination required.
In addition to hydrocolloids, new work is being done with hydrophilic and hydrophobic tapes and films that can help channel moisture away from the skin. These adhesive systems are formulated to manage moisture vapor transmission and adhere effectively to wet or moist surfaces or to surfaces that may become moist or wet during use. These adhesives are liquid stable to water or bodily fluids during skin attachment so that their adhesion properties are not significantly affected by fluids over the period of use. The adhesive composition is designed to be moisture vapor permeable while also capable of providing a seal against liquid leakage. Hydrophilic adhesives can additionally be formulated to allow for multiple re-applications without losing adhesive properties.
The Role of the Medical Converter
Converting the best adhesives and materials into the appropriate patch design for wearable patch pumps requires the assistance of a medical converter. An experienced medical converter, like Fabrico, can help with everything from initial patch design to selection of the appropriate adhesive formulation, materials for the backing and release liner, laminating the materials and adhesives, selecting the appropriate slitting and cutting techniques, assembling and kitting the final product, and more. The medical converter can also recommend the best packaging for the patch pumps for shipment and storage until use.
Skilled design engineers can help contract manufacturers and OEMs select from servo driven rotary die-cutting, CNC die-cutting, laser die-cutting, and water jet cutting to meet the complex specifications of medical components. For example, a servo driven rotary die-cutter can maintain tight tolerances ranging from 0.015” to +/-0.005” at speeds up to 500 fpm, and is ideal for the complex, multi-layer die-cutting, and lamination that a wearable patch pump might require. For complex foam tape cutting, water jet technology provides clean edges with
If the converting process entails clean room production, Fabrico has three Class 10,000 clean rooms in its facilities, as well as an ISO 13485 certification to offer. A converter with a fully equipped test laboratory can also ensure that customer materials meet designed-in specifications before they move to the factory floor, often eliminating the need to test materials at the customer’s facility. A complete test lab offers:
- Accurate and precise part dimension measurement and verification;
- Adhesive/release liner to determine converting properties and high speed application characteristics;
- Material strength measured to ensure that material meets application requirements;
- Static shear testing to measure the cohesive strength of the adhesive to withstand a fixed load over time;
- Material weight measurement to determine adhesive coating weight;
- Microscopic imaging to determine differences between adhesive and material over time.
Manufacturers of wearable patch pumps face the pressures of reducing the cost per device and producing them at a high speed, without diminishing the quality. By partnering with an experienced materials converter, OEMs can speed up time-to-market with innovative devices that improve patient health and lower the overall cost of medical services.