Mechanical Testing of Biomaterials for Non-Engineers

Mechanical Testing of Biomaterials for Non-Engineers

Here is another post in the series called Caleb’s Corner, where our company president Caleb Horst pens some original content related to biomaterials based on his insights and experience.

Biomaterials research teams often have members from engineering, biology, medicine, and other fields.  For non-engineers it can be easy to understand why mechanical properties are important, but testing can seem complex and confusing. Here’s a quick framework to help you get started.

 

understand your objectives

Do you need to test an entity with a particular geometry or the properties of a material? For entity testing, it is often important to mimic in vivo loading, perform comparison studies and establish benchmarks. For materials testing it is important to generate a specimen with a regular geometry such as a cylinder, sphere, or dog-bone. This will enable the determination of material properties (such as Young’s Modulus) that are independent of specimen geometry.

 

choose the right technology for your application

For applied forces 50mN-50kN, conventional load cells are the best choice and are available from most major equipment providers. For applied forces 1μN-50mN, consider cantilever-based force probes such as those used in the CellScale MicroTester or the Optics11 Piuma. In general, expect force accuracy of between 0.1% and 0.5% of the load capacity of the force sensor

For 2-10μm displacement accuracy, motor/screw actuation is used by most equipment providers. For higher accuracy consider piezo-driven or voice coil-driven actuation such as used in the CellScale MicroTester or the TA instruments Electroforce line.

 

consider fixturing/test environment

Biomaterials vary widely and often require special treatment. For gripping, consider jaw surfaces (serrations, sand paper coating), gripping force (screw, pneumatic, spring closure), or alternative methods such as multi-point puncture mounting or adhesively-applied gripping tabs. Some manufacturers are happy to help in this regard.

Also consider the importance of maintaining hydration and physiological temperatures. Most manufacturers can provide this, but often at additional cost.

 

plan for test validation

Most test systems will provide a means to calibrate system force and displacement. Many manufacturers have integrated imaging systems which can provide valuable qualitative and quantitative information. These images/videos can also be used effectively in presentations and publications.

equipment sourcing tips

  • ask for demonstrations (online or in person)
  • ask for sample testing with your materials or a similar substitute material
  • search academic publications for researchers who have done similar testing
  • Utilize manufacturer technical support to provide advice on test protocols, fixation, and other aspects of testing.

Happy researching!

Caleb Horst 

President

CellScale Biomaterials Testing

To read the second post of Caleb’s Corner: Build or Buy, click here

Build or Buy? Thoughts for RESEARCHERS who need TESTING EQUIPMENT

Build or Buy? Thoughts for RESEARCHERS who need TESTING EQUIPMENT

We introduce to the CellScale Blog a series called Caleb’s Corner, where our company president Caleb Horst pens some original content related to biomaterials based on his insights and experience.

So, you’re an engineer, technologist, or DIY maker. You’ve designed and built THINGS before. Back in the day your capstone project won an award, your home is filled with IOT gadgets, and you’ve at least thought about building a robot to make some trivial aspect of your life soooo much better. 

And now you want to do some mechanical testing of biomaterials. You look around at the equipment out there, and you correctly surmise that you could probably buy what you need and build something yourself for less than 1/3 of the cost. 

I know who you are, and I know how you think. A little over a decade ago I WAS YOU. For over 10 years, I have been building and selling equipment to people JUST LIKE YOU. In these years, I have witness great DIY successes. Projects that stayed on schedule and systems worked reliably. Sadly, it is more common that DIY systems take longer than expected, cost more than expected, and in the end only work well under a narrow range of test conditions. 

Generally, I see more researchers succeeding with commercial equipment. It makes sense when you think about all the time and money that goes into building and supporting commercial systems. Our company’s first product, the BioTester, became commercially available in 2007. Every year since then we have continued to invest time and money to improve the system. From the product features, to the user interface, to the robustness of the system, to the documentation – every aspect has been continuously improved in response to the feedback from a large and diverse group of users. Not only does this level of investment improve this product, it has allowed us to create a level of experience and expertise that would not be possible for a part-time DIY system developer.

So back to the main question, build or buy? As with most difficult questions, the answer is… IT 

First, it depends on your budget. Commercial equipment is always more expensive AT THE START and if you don’t have the money then you may not have a choice. That being said, the costs may not as much as you think so it’s always worth a few inquiries.

Second, it depends on your priorities. If your goal is to develop your own engineering capabilities and/or educate as many students as possible on how to build mechanical devices, develop control circuits, and write software, then there has never been a better time to become a designer, maker, and coder. If your mandate is to efficiently complete your research goals and/or publish the most scientifically impactful journal articles as possible, then a well-chosen commercial system is usually the best

Third, it depends on the alignment between the testing you want to do and the capabilities of commercially-available test equipment. If what you want to do is standard (e.g. parallel plate compression) then your needs are well aligned. For cases where a small amount of customization is required, there are great options available. Some companies are willing to absorb some of the engineering costs associated with modifying their equipment for your application if they believe that there is a market for their newly-developed 

Build or buy? In the end, every situation is unique, and the decision is yours. If you can relate to this article and would like to talk things through, then please let us know. We have a knowledgeable and experienced team and we are happy to talk about your application with no obligation at all.

Happy researching!

Caleb Horst 

President

CellScale Biomaterials Testing

To read the first post of Caleb’s Corner: What Makes Mechanical Testing of Biomaterials Different from Manufactured Materials, click here