Portable medical devices are improving the healthcare for millions of people. Sophisticated yet affordable, these devices let users monitor their vital signs themselves at home and on the go. Products such as blood glucose monitors, heart rate monitors, ingestible gastrointestinal tract monitors and pain-blocking implants have enhanced the quality of life for those with chronic or acute diseases and conditions.

The coming years will continue to see many new products powered by innovative semiconductor devices.

Electronic patch which bends, wrinkles and stretches like skin, can contain electronic components for sensing, communication and relaying information from the body to a machine (Image courtesy: www.smartplanet.com)
Electronic patch which bends, wrinkles and stretches like skin, can contain electronic components for sensing, communication and relaying information from the body to a machine (Image courtesy: www.smartplanet.com)

Benefits of going small
While the trend towards miniaturisation is fueled to a large extent by the drive to reduce cost by leveraging the cost advantages generated by Moore’s Law, there are other factors too at play. The most significant among these is the increased focus by semiconductor suppliers on the medical area. Many of them are coming out with more and more solutions tailored to particular applications. The longer-term rationale is that by enabling miniaturisation with more tailored solutions, new markets and users will be created. This will increase volumes and thus financial return on the investment.

A case in point is ultrasound. Traditionally, ultrasound machine was a cart-based unit. More recently, handheld devices have become available with the market no longer limited to hospital use. These devices are little bigger than a mobile phone, packing higher-density measurement electronics such as the AD9278 octal-channel ultrasound receiver from Analog Devices. These miniaturised ultrasound devices have the potential to find their way into the hands of every medical doctor, making ultrasound diagnostics a routine procedure in clinics. One day, they could even replace the stethoscope as the main diagnostic tool of the profession.

Another important driver is the emergence of open mobile phone platform. We are starting to see devices such as glucose meters, heart rate monitors and even pulse oximeters based on mobile phone platforms. The decision to throw open the iPhone and Android platforms has brought about a revolution in medical and healthcare applications. The ultra-low cost and easy availability of mobile phones are compelling arguments in favour of their use in medical field.

One concern, though, is the level of control over such applications. Regulatory bodies such as the Food and Drug Administration (FDA) in the US have been caught off guard by the flood of new devices, and they are now scrambling to address the issue.

Another concern relates to device longevity. The two-year life-cycle of any mobile phone model does not match well with the expected lifecycle of a portable medical device, which could be seven years or more. This raises concerns regarding component supply and product support.

Third is the emergence of low-cost communication standards—both wired and wireless. Larger medical devices are typically used in a hospital or laboratory setting, and results often centralised via computer subsystems connected to a wired Internet connection. The same need for storage of results exists with portable equipment too.

The emergence of wired communication standards such as USB and wireless standards such as Bluetooth have played an important role in easing the communication design and data interoperability challenges. In the wired domain, USB has become ubiquitous, but the wireless situation is still in a state of flux, with Bluetooth (especially Bluetooth Low Energy), Zigbee, the upcoming Medical Body Area Network (MBAN) standard and several others vying for dominance.

Components at the heart
A major trend is the development of devices that can be used by people who have no special training. The component at the centre of this trend is the microcontroller unit (MCU). Making smarter portable devices calls for more capable MCUs. The MCU applies algorithms and programmed data in order to accomplish the intended function of the device.

Besides the MCU, most portable medical-electronic devices have at least one sensor to convert temperature, pressure, sound, electrochemical reactions or some other physical quantity into an electrical signal. These signals often need some level of processing before these can be used by the MCU. This processing is done by analogue components, such as operational amplifiers, filters and analogue-to-digital converters.

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