Medical Adhesive Testing Basics

Medical Adhesives Mechanical Testing Solutions

Adhesives used in medical applications require mechanical testing to ensure their strength, durability, and compatibility with various substrates. Sutures are often classified as medical adhesives because they function to mechanically close and secure tissue interfaces, similar to how adhesives bond surfaces together.

ADMET testing systems are trusted by leading medical device manufacturers, universities, and research laboratories to determine the mechanical properties and endurance limits of biomaterials, medical devices and implants. Our systems meet FDA 21 CFR part 11 requirements and are capable of performing tension, compression, flexural, adhesive, torsion, axial-torsion and planar biaxial tests according to ASTM and ISO standards. Our ability to design a system to fit specific needs allows ADMET to provide testing solutions for even the most unique and demanding applications.

Types of Medical Adhesives

Tissue adhesive for the topical approximation of skin

A tissue adhesive for the topical approximation of skin is a device intended for topical closure of surgical incisions, including laparoscopic incisions, and simple traumatic lacerations that have easily approximated skin edges. Tissue adhesives for the topical approximation of skin are Class II medical devices and may be used in conjunction with, but not in place of, deep dermal stitches.

Tissue adhesive for non-topical use

A tissue adhesive for non-topical use is a Class III medical device that is used for adhesion of internal tissues and vessels. Examples of use include the embolization of brain arteriovenous malformation and ophthalmic surgery.

Tissue adhesive with adjunct wound closure device intended for the topical approximation of skin

A tissue adhesive with adjunct wound closure is a Class II medical device intended for topical application only to hold closed easily approximated skin edges of wounds from surgical incisions, including punctures from minimally invasive surgery, and simple, thoroughly cleansed, trauma-induced lacerations.

Types of adhesives include:

1. Cyanoacrylate Adhesives: Quick-setting and used for minor wound closures.
2. Silicone-Based Adhesives: Known for flexibility and biocompatibility, often used in skin attachments and prosthetics.
3. Epoxy Resins: Offer high mechanical and thermal resistance; used in bonding medical devices.
4. Acrylic Adhesives: Provide high tensile and shear strength; adhere well to various materials.
5. Pressure-Sensitive Adhesives (PSAs): Used in medical tapes and patches; adhere with applied pressure.
6. Polyurethane Adhesives: Versatile with excellent wear resistance; often used in flexible medical devices.
7. Fibrin Sealants: Derived from blood components and used for hemostasis during surgical procedures.
8. Hydrogel Adhesives: Water-based and gentle on the skin; commonly used in wound care and ECG electrodes.

Depending on the type of test you are conducting, extensometers can accurately determine specimen extension during testing. Deflectometers, on the other hand, can help calculate the deformations that occur during three or four point bend tests or compression tests. ADMET offers several types of deflectometers and extensometers.

Sutures

Sutures often considered the baseline for wound closure techniques, play a crucial role in the medical field. When it comes to developing new medical adhesives, sutures serve as a comparative standard for evaluating the efficacy and mechanical properties of adhesive products. This assessment includes tensile, shear, and peel tests to ensure that medical adhesives can meet or exceed the performance characteristics of traditional suturing methods. By understanding the mechanical benchmarks set by sutures, developers, and manufacturers can optimize adhesive technologies for various medical applications.

Common Medical Adhesive Test Types & Standards:

Peel Testing is a mechanical testing procedure used to measure the adhesive strength of materials by assessing the force required to separate two bonded surfaces. Some peel testing standards of medical adhesives include:

• ASTM F2256 Strength Properties of Tissue Adhesives in T-Peel by Tension Loading
  • Tensile test method to compare and characterize the peel strength of different types of tissue adhesives
• ASTM D3330 Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape
  • Six different test methods for testing the peel adhesion strength of pressure sensitive tape

Shear Testing is a mechanical test that evaluates the ability of a material to withstand forces that can cause the internal structure to slide against itself. Some shear testing standards of medical adhesives include:

• ASTM D3654 Standard Test Methods for Shear Adhesion of Pressure-Sensitive Tapes
  • Test method to measure the ability of pressure-sensitive tapes and labels to remain adhered under constant load applied parallel to the surface of the tape and substrate
• ASTM F2255 Strength Properties of Tissue Adhesives in Lap-Shear by Tension Loading
  • Tensile test method to measure and compare the lap-shear strength of tissue adhesives

Tensile Testing is a mechanical test that involves pulling a material apart and measuring the force and deformation to assess its strength, elasticity, and elongation properties. Some tensile testing standards of medical adhesives include:

• ASTM D882 Standard Test Method for Tensile Properties of Thin Plastic Sheeting
  • Test method to determine the tensile properties of plastics in the form of thin sheeting
• ASTM D2256 Thread and Yarn Tensile Testing
  • Test method to determine the breaking strength, elongation, and energy of threads, yarns, or other single strand textiles. (Often used for sutures)
• ASTM F2258 Tensile Strength of Tissue Adhesives
  • Tensile test to measure and compare the adhesive strengths of tissue adhesives
• ASTM F2458 Wound Closure Strength of Tissue Adhesives
  • Tensile test method to measure and compare the wound closure strength of tissue adhesives

Mechanical Properties Measured

Bonding Strength: Mechanical testing assesses the adhesive’s ability to create strong bonds between different materials, tissues, or surfaces. This is crucial for adhesives like wound dressings, where secure adhesion is required for effective wound closure and protection.

Material Compatibility: Medical adhesives must be compatible with a wide range of materials, including skin, tissues, and other medical components. Testing helps identify potential interactions or reactions that could compromise the adhesive’s performance.

Durability: Adhesives used in medical applications must maintain their bond strength over time. Mechanical testing simulates real-world conditions to assess how the adhesive withstands various stressors and maintains its integrity.

Tensile Strength: Medical adhesives must have an appropriate tensile strength for their applications. Tensile strength measures the maximum stress a material can withstand in axial tension before failure. High tensile strength is critical for applications like surgical sutures and other wound closing adhesives, ensuring that the adhesive can withstand the mechanical stresses it will encounter in a physiological environment.

What equipment do I need for medical adhesive testing?

To perform mechanical testing on medical adhesives, you will need a testing frame equipped with the appropriate fixture to clamp the test specimen, a load cell, and a controller. The type of testing system required will be dependent on the adhesive tested, the type of test, and the required calculations.

Testing Frame

eXpert 7600 – Single Column Testing Machine

The eXpert 7600 is a popular medical adhesive testing machine due to its ability to produce accurate results in an affordable and compact package.

learn more

eXpert 5600 – Modular Testing Machine

The eXpert 5600 series testing machines feature configurable frame components and a detachable actuator, giving you the ability to configure your medical adhesive testing system in a variety of vertical or horizontal orientations.

learn more

eXpert 4000 – MicroTester

The eXpert 4000 series MicroTesters measure very low forces and small displacements on medical adhesives that can often be difficult to hold. Most 4000 series MicroTesters can be configured for testing in temperature-controlled fluid baths to replicate the desired environment.

learn more

eXpert 5900 – Fatigue Testing Machine

The eXpert 5900 is ideal for performing fatigue testing on hard tissue adhesives that require an axial fatigue load. The 5900 series systems can be equipped with special fixturing to mount a variety of adhesives and can be equipped with an environmental bath to test performance in the desired physiological environment.

learn more

Custom Medical Adhesive Testing Systems

Do you require a customized testing solution? ADMET Engineers will work with you to design the right system to meet your material testing needs.

talk to our engineers

Testing Fixtures

Medical adhesives, also known as medical glues or surgical adhesives, are used to bond or adhere tissues and are intended for used for wound closure. Sutures and staples are also used for similar purposes. Medical adhesives are not strictly classified as medical devices and can be mechanically tested in various test types to ensure safety and efficacy in medical applications. Below we will explore different types of medical adhesive tests and the required fixturing to perform them.

90 Degree Peel Fixture

Requires FS-PL-90 fixture and a vise grip or eccentric roller grip.

Custom Medical Adhesive Test Machine

eXpert 8600 – Configured to test medical adhesives and tissues in a heated fluid bath.

T-Peel Test Fixture

eXpert 7600 performing a T-peel test, similar to ASTM F2256. Requires two vise grips and a flexible substrate.

Floating Roller Peel Test Fixture

eXpert 7600 performing a floating roller peel test, similar to ASTM D3167. Requires an FS-PL-ASTM D3167 floating roller and a vise grip or eccentric roller grip.

Loop Tack Strength Test Fixture

eXpert 7600 performing a loop tack strength test, similar to ASTM D6195. Requires a vise grip and a cube fastened to the bottom of the testing machine.

180 Degree Peel Test Fixture (Three-headed)

eXpert 5600 performing ASTM D903 Three-Head Peel Test.

Suture Tensile Test – Thread Grips

eXpert 7600 performing ASTM D2256 with GT-0.2T grips.

Environmental Bath

Most of ADMET material testing machines can be equipped with an environmental bath to perform testing in the desired physiological environment.

Medical Adhesive Testing Videos

ADMET systems can be configured to test a vast array of medical adhesives and test types. Check out our Medical Adhesive Testing Playlist below to explore the capabilities of our testing systems (Click on the top right playlist icon to view all of relevant videos).