ample, the batteries in a human implantable
cardioverter defibrillator (ICD), also referred
to as a pacemaker, last anywhere from four
to ten years.
In many drug delivery systems, such as
implantable infusion pumps, the battery
life is even less due to the complex dosing
protocols. Some pumps may last from a few
weeks to a few months, thus requiring frequent replacements. Such replacements are
not only inconvenient and time consuming,
but can also be downright costly. With the
large numbers of sensors expected to come
online, implant surgeries just to replace
batteries in an implanted device would soon
become impractical. So how could one replenish the energy source for these sensors?
Fortunately, advances in semiconductor
technology provide the hope of perpetually-powered electronic implants. New
integrated semiconductor circuit technology
will play a critical role in energizing these
sensors and implantable devices. After all,
the body itself is a vast pool of energy.
Movement or motion, glucose, and heat are
some of the potential energy sources within
the human body. New ICs have the capability to extract tiny amounts of ambient energy
from sources such as heat, light, vibration,
and even radio-frequency energy.
But how will it all work? The power extracted is likely to be very small. Almost all
nano-generators are scavengers of energy
from minute movements of fluids, heartbeats, diaphragm, and respiration activities.
Others also scavenge from motion of the
limbs. Because of the minute amounts of
energy scavenged, this energy will need to
be boosted to make any difference. This is
where new IC technology plays a critical
role. Ultra-low power boost converters and
chargers (energy management ICs) can
play a huge role in the boosting process.
Advances in semiconductor technologies have led to a whole new category
of ultra-low power semiconductor ICs,
including ultra-low power microprocessors,
energy management ICs, and RF transceivers (for the radio link in case wireless data
capability is desired).
Heat produced in the body is a particu-
Case in Point: Indus Instruments
larly appealing energy source. It is always
present. Could there be a way to utilize the
heat from the human body itself to power
medical devices? It would require a way to
first convert the body heat into usable elec-
trical energy. Thermoelectric generators –
devices that convert a temperature gradient
into electrical voltages – are often used in
industrial applications. A small-sized gen-
erator could be placed subcutaneously to
take advantage of the temperature gradient
between the internal tissue and the skin to
be able to produce small amounts of power
that can be harvested to recharge small
batteries, thus extending the run-time. De-
signed correctly, such a system can provide
perpetual power to small devices such as
infusion pumps and other similar devices.
Other promising technologies for energizing the electric body are wireless charging,
and wireless RF energy harvesting. Their
contactless nature is well suited for medical
applications. Innovative companies are using
these technologies to differentiate themselves. For example, Indus Instruments is a
company that specializes in turnkey design,
development, and manufacture of custom
A block diagram representing a typical energy harvesting system used in self-powered sensors.
Energy Extracting IC
One example of an IC that can extract energy from
heat, vibration, and RF waves, is the Texas Instruments
(TI) bq25570 ultra-low power energy management
integrated circuit. This IC can extract, condition, and
manage the small amount of power produced by
nano-generators, or harvesters as they are sometimes
called. The extracted energy can be stored in a storage
element (battery) for later use. This energy is usually
in the order of microwatts to milliwatts, but still enough to power ultra-low power ICs such as
an ultra-low power MSP430G2553 microcontroller (MCU), or a SimpleLink CC2541 Bluetooth low
energy wireless MCU from TI. The bq25570 IC also allows an innovative method to recharge
implantable devices using body heat.