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Tech Primer
Vital-Signs Monitor Chip
 A
new disposable wireless electronic patch has been designed by Toumaz Technology
to monitor a person’s vital signs, which can be beneficial for hospitals,
home patients, the elderly and even top athletes. An ultralow-power system-on-chip
(SOC) runs a wireless body-area network capable of sensing temperature, heart
rate, respiration, electrocardiogram (ECG) signals, and other vital signs.
Though there are other vital signs monitors available in the market place, none
of them can provide features such as fitting in an ultrathin patch, cheap enough
to be disposable, that consumes as little power as Sensium does. This is an
alternative to existing expensive, high power consuming and bulky devices.
Structure and working
It contains a wireless transceiver that consumes 2.6 mA to transmit and 2.1
mA to receive from a power supply of just less than a volt. In order to keep
power consumption low, many systems and functions usually done using power-consuming
software are integrated into the chip. Apart from the transceiver, the chip
integrates a digital controller, a temperature sensor, an interface for up to
three vital-signs sensors, and signal-processing circuitry. It even contains
a custom communications protocol to respond quickly to weak signals and assure
data reliability.
The operating frequency of the transceiver is in the range of 862- to 870-megahertz
European Short-range Device (SRD) frequency bands and the 902- to 928-MHz North
American Industrial, Scientific and Medical (ISM) bands. Up to eight transceivers
can connect on a single frequency to a base station located in a hospital ward.
From the ward, the data gets forwarded to hospital computer systems.
Low cost
This chip makes use of a printed zinc-based battery manufactured by Israel’s
Power Paper which is cheap and, unlike lithium-based batteries, environment
friendly. The battery has a lifetime of around five days, a period after which
electronic patches generally begin to look old, irritate the skin, and need
to be replaced anyway. This battery contributes to the system’s low cost.
Apart from that, the cost is mostly reduced by integrating the entire monitor’s
functionality into a single 4 by 4 by 3 mm slice of silicon instead of spreading
it over several chips. In addition to the low-power chip, the vital-signs monitor
patch includes two or more noninvasive sensors and, depending on the vital signs
to be monitored, can be as small as 25 mm on a side. Once this technology is
commercially mass-produced the initial price would be in the range of $5 and
$10 which will eventually fall below $5.
Toumaz has conducted clinical testing of the vital-signs monitor chip, but the
patch still requires going through the safety check.
For further information, visit: spectrum.ieee.org/feb08/5969
—Kushal Shah
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