5 Things to Keep in Mind When Trying to Reverse Engineer Adhesive
The process of reverse engineering is demanding work: an analyst initially works with limited information about a product and uses that information to analyze it to discover its composition. When reverse engineering is performed for a product that has a chemical composition--as compared to a machine or a software program--the process is also referred to as deformulation. The major and minor components of the composition are separated and broken down in order to be identified.
Considerations involve the unexpected variables in the product's manufacturing and testing. For these reasons, it's essential to understand the various types of adhesive used in medical devices as well as some of the fundamental difficulties that may arise during reverse engineering.
Types of Adhesives Associated with Medical Devices
Adhesives used for medical devices are manufactured from synthetic and biological materials. They can be incorporated into single-use or reusable devices and typically involve the bonding of plastics and metals. Medical adhesives can be used in forming permanent bonds as is often the case in medical device assembly, or they form temporary bonds as with bandages. They vary in bonding qualities when applied to different substrates and require different methods of applications.
The three main types of adhesives used in medical devices are:
- Pressure-sensitive adhesives (PSAs). Fabricated in woven or nonwoven materials, PSAs require pressure to adhere to a substrate. They are frequently used for skin bandages.
- Dissolvable adhesive films. When exposed to variables such as heat or fluids (including biological fluids), these films dissolve at a specific rate. They are used for delivering therapeutic agents or for adhering to stents and other medical devices.
- Electrical conductive adhesives. Manufactured in film form or gel form, electrical conductive adhesives consist of materials that are compatible with medical device sensors and electrodes.
5 Things to Keep in Mind When Trying to Reverse Engineer Adhesive
Although the abundance of process details may become overwhelming at times, reverse engineering requires that you maintain a "big picture" view of the work at hand. The following are 5 essential things to consider while you are deformulating an adhesive.
1. What Is Your Goal?
Reverse engineering can be performed for a variety of contexts such as competitive analysis, patent infringement inquiry, failure analysis, or new product research and development. The framework chosen will drive the scope of your work and the type of analysis you need to perform.
For example, if you need to find out more about a proprietary component in an adhesive for competitive analysis purposes, you might want to dig deeper and perform a higher-order analysis. Alternatively, if you are comparing variations in batch-to-batch samples, you may not need such detail.
2. Make Sure that You're Using the Right Techniques
Reverse engineering an adhesive will require some separation of components in a sample. Multiple techniques will be necessary in order to find the specific information needed about the chemical formulation.
Analytic chemistry techniques require advanced instrumentation such as gas chromatography/mass spectroscopy (GC-MS), liquid chromatography/mass spectroscopy (LC-MS), nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC) and Fourier-transform infrared spectroscopy (FTIR), among others. All of these instruments identify molecules in a mixture, with varying degrees of specificity and sensitivity.
LC-MS and GC-MS, for example, are used to separate and identify components according to the amount of volatility they have. LC-MS is often used to identify less volatile components, while GC-MS is relied upon to identify more volatile components.
An NMR analysis can separate components in a complex sample and present those components as individual spectra. If GPC is added to this analysis, molecular size for the sample's components can be measured.
FTIR is especially useful for identifying polymers in adhesives. It utilizes a range of infrared spectroscopy to identify components that contribute to an adhesive's bonding and curing properties as well.
3. What Are Your Requirements for Testing?
Your initial knowledge about the product will determine the testing standards that you decide on using. If you know neither the type of adhesive you're testing nor its application, it is best to go with a proven deformulation method. Other things to consider are whether you have requirements for product performance or whether there are regulatory or industry standards that you need to incorporate into your project.
When testing, you will also need to consider leachables, which are commonly found in adhesives. These impurities include dyes, fillers, and plasticizers that may combine under certain conditions with the primary drug product. Sometimes new species of leachables are formed when adhesives come in contact with the drug. An example would be leachables formed when a drug and its adhesive patch delivery system have contact. Structured testing with a combination of techniques will be necessary.
4. Consider the Variables that Can Change Adhesive Characteristics Post-Application
Several variables can alter the way an adhesive works after application. Here are some important ones that can alter adhesive performance:
- Heat and humidity. Hot-melt adhesive, for example, is used in medical device assembly that increases in viscosity as heat is applied.
- Pressure. The amount of pressure applied to an adhesive can change after application. Bonding quality is a related variable that is dependent on the surface energy of the substrate.
- Duration. Pressure applied to an adhesive is also related to how long it needs to stay in place to adhere to the substrate. This differs from a structural adhesive that permanently bonds to a substrate without pressure.
- Sterilization. Some adhesives do not withstand the rigors of sterilization. Others, such as autoclave tape, are designed to not only withstand the sterilization process but also change appearance afterward to signal a completed process.
5. Acknowledge the Possibility that You Might Obtain Limited Results
While you might be able to identify major components of an adhesive, identifying individual proprietary components might be much more difficult due to sensitivity and interferences in the analytical techniques. Alternatively, if there is a high number of compounds in the adhesive, it may not be time- or cost-effective to pursue reverse engineering beyond a certain level of analysis. You also might find that the recombination of components following analysis does not guarantee that you will be able to replicate the formulation's original manufacturing process.
The analysis of an adhesive with an unknown composition can be like putting together pieces of a puzzle. If you perform a few tests, those few pieces provide a basic "picture" of the adhesive. The more tests you perform, the clearer the picture becomes. Over time, you will have enough information to meet your original goal of reverse engineering.