Microelectromechanical Systems (MEMS), as the name implies, are miniature devices composed of mechanical (springs, deformable membranes, vibrating structures) and electrical (resistors, capacitors, inductors) components that, together, are able to sense and report on physical properties of the environment in which they are deployed, or, when signaled to do so, are able to perform some kind of controlled actuation.
In the medical applications market, MEMS components are used in diagnostic, monitoring, surgical, and therapeutic devices. These devices employ MEMS as pressure sensors, temperature sensors, flow sensors, accelerometers, optical image sensors, and silicon microphones, among other uses.
The techniques used to fabricate MEMS devices are similar to the techniques used to make silicon-based integrated circuits (i.e., microprocessors or memory chips), which means that MEMS manufacturing can enjoy the kind of scaling advantages and manufacturing efficiencies that have long been a hallmark of integrated circuit (IC) fabrication.
Additionally, MEMS devices have several advantages for medical applications that make their use attractive: the 2 to 100μm-sized features typically found in MEMS devices are compatible in size with living cells and fine physiological structures in the human body. MEMS devices are manufactured with materials such as silicon, silicon dioxide (glass), precious metals like titanium, gold, and platinum, and organic materials like Parylene, that are biocompatible.
With the close family resemblance to integrated circuit manufacturing, MEMS devices are easily integrated with electronics components to include signal processing and analysis capabilities and wireless telemetry functions for ingestible or implanted MEMS devices. This enables the powerful combination of integrated performance sensing with wireless data transfer, all in a compact form factor.
Table 1 presents the world top five medical device makers by revenue and by selected MEMS-based activities associated with them.
Why the Need for MEMS-Enabled Medical Devices?
According to GE Sensing, Inc., the reason is that “Today’s patient care demands the ultimate in accurate and reliable monitoring of critical parameters.” MEMS sensor-enabled devices are one proven way to deliver that result. (www.ge-mcs.com/download/temperature/Sensors_for_healthcare.pdf )
MEMS pressure sensors have a long history in medical applications, and have been used in non-invasive medical equipment, such as respiratory gear and blood pressure cuffs, since the 1980s. More recently, MEMS pressure sensors have been used for invasive applications as well, including as catheter tip sensors, or as an implant reporting on blood pressure (systolic and diastolic), heart rate and cardiac output, around the clock. Figure 1 shows an optical photograph of a MEMS pressure sensor.
Again, per GE, “Disposable pressure sensors are used primarily during surgical procedures and in the ICU to monitor patient heart rate and blood pressure. Pressure sensors in ventilator machines watch patients with respiratory illness or people on life support, helping control the amount of air pressure delivered to a patient’s lungs. They also monitor people with sleep disorders. During neonatal care, pressure sensors help physicians check the pressure within an expectant mother’s uterus.”
Transparency Market Research estimates that “The global MEMS medical applications market was valued at USD 1.8 billion in 2012 and is expected to grow at a CAGR of 20.2% from 2013 to 2019, to reach an estimated value of USD 6.5 billion in 2019.”
MEMS pressure sensors have the largest single piece of the medical applications market, at $486 million in 2012, and are expected to grow at a compound annual growth rate of 18.7% from 2013 to 2019 as they find their way into even more medical devices.