Testing objects is part of our everyday lives. We test objects in different ways and for different reasons, learning about how something new functions or answering a simple question, such as: “Is this old looking chair going to break if I sit on it?”

In the everyday, we test objects that we are unsure of or have little confidence in, but testing a device, no matter how simple it is, is also an essential part of the product development process. This is because testing serves multiple purposes: it validates whether a device is safe and fit for purpose before the user operates it and it is used to direct the design of the product during its development – in-other-words, testing needs to happen from concept generation to final deployment.

A general rule is that the more complex the device, the more complex the testing. Similarly, the more contact the device has with humans, the more rigorous the testing needs to be – especially if the device has potential to harm the individual. Testing the capsules developed in the Sonopill project presents a significant challenge as not only are the capsules complex, but they come into direct contact with humans and so must adhere to strict regulatory processes that govern their safe use.

We typically need to answer three broad questions before testing: What component(s) do we need to test, at what stage do we test at, and what environment do we test in?

Every single component of the medical capsule must be tested to ensure it meets the safety requirements. This testing is mandatory and, for a researcher, more of a chore than an interesting task! And we already acknowledged that testing should happen at all stages of development to direct the design and validate its functionality and safety. The last question on what testing environment to use is by far the most interesting and is something people often ask when they hear that we develop medical capsules.

So where do you test something that is designed to be used in the completely unique environment of the human digestive tract?

Ultimately, we want to test it exactly where it is going to be used … in human! However, as I am sure you can imagine, this is not always possible – especially during development where we are not confident in the functionality and safety of our device. Partly for ethical reasons and partly because it is useful to do so, we tend to follow a step-by-step approach of increasing environment complexity.

Step 1: The mental test. During the conception of a new design, we use our experience to mentally test the feasibility of the device; imagining its fabrication, its operation and any potential issues.

Step 2: The computer simulation. This is not always necessary, but we are able to test entire devices in simulation and validate their core functionality – do all the mechanisms operate as intended?

Step 3: The benchtop. Here we simply switch on and test the device in the lab. This answers more fundamental questions on the success of the fabrication process and whether the core functionality is there. Do the electronics power-on without spontaneous combustion? Do the sensors or actuators work as intended? We might spend some time here as we tweak the design to achieve the desired technical and safety performance.

Step 4: The phantom. No, not ghost, but a synthetic replica of the target environment. This is a challenging step because no matter how much time or money you spend on it, chances are you will not come close to mimicking the exact conditions found in the human body – it is far too complex! We make a compromise and use a synthetic alternative that has the same broad properties. For example, we might use a soft silicone tube with a lubricant to simulate the intestine. In this environment we can really begin to assess how well the device functions as a whole

Step 5: Benchtop Ex vivo. Here we remove (Ex) real biological tissue samples (vivo) and use them to test our device in the lab. This allows us to monitor the interactions with the complex tissue substrate, but in the more controlled environment of the lab.

Step 6: Human cadaver. A sensitive topic, but the closest thing to testing in a living human is to use a thiel cadaver. These are donated and are incredibly useful for training doctors and testing new medical technologies. We can truly assess the feasibility of our device in this environment and make any final modifications to the design based on the data we get.

Step 7: In-human. After passing a strict regulatory review, meeting ethical and safety standards, and having completed hundreds of hours of testing, we are finally ready to test our device in humans. A clinical trial is arranged and volunteers recruited. This is the ultimate goal when developing medical technologies and the final major testing step before deployment. 

First published: 26 January 2018

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