Understanding pressure changes in the body can provide physicians with valuable information about how to better treat patients, direct targeted drug treatments or improve device performance. While adding pressure sensing capabilities to a device may seem like a simple addition to open the doors to an abundance of information, there is a level of expertise required to select a sensor, determine how to integrate it, achieve optimal sensor performance and stay within the cost requirements.
Consider the standard ventricular assist device (VAD). VAD's today measure motor current to ensure they have proper placement and provide feedback on flow rates. Today’s VADs either maintain constant flow or pump at a steady rate with no active feedback from the patient. The next generation of devices might include active feedback via pressure data. This would allow regulation of pump speed to maintain adequate perfusion according to the demands of the patient. A human’s internal vasculature is naturally sensitive to cardiac pressure measured via baroreceptors that allow for real-time regulation of heart rate and cardiac output. A pressure sensor would enable a pump to provide a similar natural modulation of blood pressure to allow nocturnal/diurnal changes in blood pressure during sleep and/or waking.
Real-time measurements to provide active feedback have the potential to improve device efficiency and increase therapy effectiveness. This all sounds great, but the question is, “How does a company equip their teams with the expertise needed to successfully integrate a sensor that functions with the device and application requirements?”
Rather than investing the time and resources to develop internal expertise, a sensor integration partner can reduce the risk and expense, plus speed up the development timelines. According to the article, “Collaboration – The future of innovation for the medical device industry,” published by KPMG, the next wave of innovation in medical devices will occur when companies combine their expertise to develop these next generation products.
How to navigate sensor integration
All sensor integration projects have unique challenges and timelines based on the type of device, sensing requirement, and duration of device use. Decisions about sensor size, absolute or gauge, or a custom design factor into the process. Understanding the environmental factors that affect sensors and choosing the right sensor from the beginning can significantly reduce development delays.
Testing for feasibility is a critical stage in the sensor integration process. Each device will have different performance and durability requirements driven by the intended application. This can impact wire integration, sensor placement, and encapsulation needs. Assumptions on sensor performance for the intended application can be tested with early rapid feasibility prototyping. This allows multiple sensor configurations to be trialed to quickly eliminate design flaws and identify and optimal path forward. For example, when comparing an orthopedic pressure application to a cardiovascular application, the device size, sensing requirements, and durability needs can all vary greatly.
One of the biggest challenges is how to encapsulate the sensor to withstand corrosive fluid environments for extended periods of time, especially for many newer devices that require extended implantation in the heart or vasculature. While adding blood pressure measurement to these devices can improve functionality and provide additional patient data feedback, this introduces added complexities to sensor integration and encapsulation that must be factored into the design to adequately meet the customer requirements.
Once a sensor is selected and design feasibility is proven, sensor encapsulation and coating selections can present unique challenges that significantly affect sensor performance. For example, a sensor requiring ultra-low drift performance may experience high drift rates when hydrated inside the body if the sensor is coated with the wrong material or encapsulated with too much or too little protective material. Experience with material selection can optimize the process, reduce the number of iteration design cycles, and increase speed to market.
Drift is another challenge that is not always well understood by inexperienced teams. Many factors combined contribute to drift including changes in atmospheric pressure, temperature and hydration. Changes in temperature and hydration can be accounted for by pre-soaking the sensor for a specified period prior to use. However, this is not always possible in real world applications, especially when the device is meant to be used in an emergency. Understanding this limitation up front is critical so that drift can be optimized during the development of the manufacturing processes.
Finally, once all the challenges above are overcome, the manufacturing process must be developed and optimized to meet yield and throughput requirements. The incredibly small size of many of today’s sensors, some of which measure less than 200 um across, pose unique manufacturing challenges that can be greater than or equal to the timeline of the original sensor integration process. Developing this infrastructure from the ground up can require a significant capital investment which should be factored into the overall sensor development effort.
Millar OEM Solutions – Pressure Sensor Integration Partner
Choosing the right partner, such as Millar OEM Solutions, who is backed by 50 years of experience in MEMS sensor integration, can start the integration track off right. Collaboration is key when solving today and tomorrow’s medical challenges especially when cost limitations, speed to market and sensor accuracy are more important than ever.
Visit Millar Speaking Sessions at Medical Sensors Design Conference
Tuesday, June 25th
Millar’s CEO/President, Tim Daugherty, will be participating in the What’s Next for IoT & Connected Care? Panel on June 25th at 4:10 pm during the Medical Sensors + Design Conference 2019.
Wednesday, June 26th
Valor Thomas, OEM Business Development Manager, will be presenting on the topic “Smarter Devices Enabled by MEMS Pressure Sensors” in the Medical Sensors Design Theater during the Sensors Expo and Conference 2019 on June 26th at 1:35 pm.