This is copy right By Mohammed Kaleem. It is very novel and innovative presentation.

1. Device turns body heat into Energy to Power
wearables

2. “Skin-like” properties represent a different form of technology that
is now beginning to emerge from research laboratories into pre-
commercial prototypes.
The devices exploit materials and layouts that lead
to system-level physical properties (thicknesses, moduli, physical
and thermal mass, etc.) that approximate those of the skin itself.
The outcome is an unclear mode of integration with the skin
through direct lamination, thereby avoiding limitations of
predictable hardware to provide continuous streams of clinical
quality data on physiological health (11–12).
The most highly functional systems of this type require wired
connection for power delivery and/or data acquisition.
Wearable devices

3. A lightweight device established by Montalbano E, 1998 that
turns body heat into electricity is the newest potential
substitute to batteries for wearable technology.
The device, a wearable thermoelectric generator (TEG) that
makes use of the temperature differential between a person’s
body and the ambient air to generate electricity.
“Current wearables have battery life time of several days to
several months depending on their functionality,”
Efficient wearable thermoelectric generators that convert body
heat to electricity for turning on the electronic sensors [of
wearable tech].”

4. Wearable Sensor Node Hardware Design
Hardware design requirements are minimum size, efficient power
management and a compact rechargeable battery system.
Figure 1 shows the block diagram of the developed sensor node,
and Figure 2 shows its photograph (1).
It consists of a PIC18F26J50 8-bit microcontroller (C), with
Nano Watt technology, selected for its cost-characteristics
tradeoff and low power consumption.
It owns energy-saving working modes and independent clock
lines that can be addressed to different peripherals according to
its timing requirements.
It can be dynamically powered at a voltage ranging from 2.0 V to
3.6 V, with a quiescent current of 6.2 A in non-sleep modes (1).

5. Fig.1 Wearable sensor node block diagram.
Fig. 2Wearable sensor node photograph: (Left) without XBee; (Right) with XBee

6. Microcontroller
Manages the node operation, i.e., sensor acquisition; data collection
and storage; building of the data frame to be sent by the radio
frequency (RF) transceiver; sending of the data frame to the RF
transceiver through an RS-232 protocol; and monitoring of the node
state (energy mode, inialitization, etc.).
The node RF transceiver is an XBee module with a wire antenna to
reduce the size.
It includes the DM-24 firmware from DigiMesh that works in the
2.4 GHz
Industrial-Scientific-Medical band with an IEEE 802.15.4 protocol
running in the transceiver, making compatible the connection of
this device to a deployed wearable wireless sensor network W-
WSN and allowing drawing up of its communications structure.

7. Sensor node
Novel and compact power supply system.
It consists of a MCP73833 battery charger circuit from Microchip,
a rechargeable battery and two low dropout (LDO)
It regulates to provide the power voltage levels required by the
different components.
The selected battery is a 3.7 V and 800 mAh Lithium Polymer
with a small size.
The voltage regulators provide stable, well-defined voltage levels
from the decreasing battery voltage.
MCP1725 LDO voltage regulator provides a 3 V constant voltage
to power the XBee RF transceiver.
The second LDO regulator provides a constant 2.5 V level to
power the rest of node electronics.

8. Sensors
Contained on a specific printed circuit board (Figure 3) connected
to the sensor node through a pin in-line connector.
This permits an easy replacement for damaged or obsolete sensors
without modifying the main node architecture.
This technique displayed measures of humidity, temperature and
CO2 concentration.
A SHT11 provides the relative humidity and temperature
information, with an operation range of 0%−100% and −40 °C to
124 °C, respectively.
The gas detection is accomplished by a non-dispersive infrared
IRC-A1 CO2 sensor, from Alphasense [5, 6] in the range of
0−50,000 ppm to match safety applications.

10. This sensor requires 2 Hz square wave excitation, a preheating time of 30 min
and up to 40 s of response time.
Our conditioning circuitry has been adapted from [7], to fit the µC analog-to-
digital converter (ADC) input voltage requirements.
The 2-Hz square signal required by the sensor is directly provided by an
independent a stable circuit based on operational amplifier MAX4038 instead
of a digital output from the microcontroller.
Thus, the microcontroller can be set to a low-power mode, reducing the
energy consumption, while the sensor keeps always active to minimize its
response time.
Sensors 2017, 17, 365 4 of 14 response time.
Our conditioning circuitry has been adapted from [7], to fit the μC ADC input
voltage requirements.
The 2-Hz square signal required by the sensor is directly provided by an
independent a stable circuit based on operational amplifier MAX4038 instead
of a digital output from the microcontroller.

11. the microcontroller can be set to a low-power mode, reducing the
energy consumption, while the sensor keeps always active to
minimize its response time.
Three signals (reference, active and temperature voltages) in the
IRC-A1 sensor must be used to calculate the CO2 concentration,
by applying the equations given in the sensor datasheet.
However, due to the complexity of the required equations and the
use of a low-cost microcontroller as a sensor node manager, the
microcontroller includes look-up table (LUT) data that allows for
a coarse estimate of the measured CO2 levels, while an acoustic
alarm using a buzzer included in the board is activated
when concentration exceeds a predetermined level.

12. Fig. 4 shows the operation flowchart wearable sensor node soft
ware.
Once the power is switched on first time, the microcontroller is
firstly configured using locally-stored default parameters:
duty/sleep timing, operation frequencies, etc.
Next, the RF transceiver is initialized following a
microcontroller request, initializing the universal asynchronous
receiver-transmitter, configuring the interrupt service routine
and starting the wireless network joint process.
Network joining requires an XBee software reset, then a
commissioning command is sent to the network coordinator
node to indicate that a new device is joining the network and
finally the transceiver is sent to sleep mode.
Wearable Sensor Node Software

13. Once both microcontroller and transceiver have been initialized,
sensor input/outputs and peripherals (such as the analog-to-
digital converter) are configured.
Configuration is completed by enabling the microcontroller to
receive interrupts from the transceiver, then driving the node to
sleep mode.
Once fully configured, the node operation consists of a main
loop, where the microcontroller is awakened by an interrupt
request from the XBee.
Next, the operation frequency increases in order to reduce the
acquisition time, the sensor data are collected, compared to the
values stored in the LUT and sent to the network coordinator
through the transceiver.

14. Finally, the operation frequency is decreased and the system goes
back to sleep mode until a new XBee interrupt is produced.

15. Initialization
µC
start
Initialization
XBEE
Enable ISR
Initialization
Sensor
Awake µC
Set µC Sleep
mode
Increase operation
frequency
Initialization
UART
Initialization
XBEE ISR
XBEE Join
Decrease
operation
frequency
Send data
frame
Add sensor
measure
XBEE Reset
Delay
Commissioning
Set XBEE
Sleep mode
Delay
ISR
XBEE
Fig. 4

16. Application and uses
The devices presented here provide battery-free, fully wireless
optoelectronic functionality in physical forms that have
properties compatible with the epidermis to allow intimate
integration with the skin for acquisition of various health
information.
An attractive feature of the NFC approach is its ability to enable
both wireless power delivery to and extraction of data from the
devices in a manner that is compatible with smartphones and
other consumer electronics.
The battery-free operation allows the systems to be engineered in
much thinner, lighter, and more wearable formats than would
otherwise be possible.

17. The data from device examples reported here provide information
on heart rate and temporal dynamics of blood flow, tissue
oxygenation, and color of the skin.
The addition of color-responsive materials expands the
functionality to allow sensing not only of the skin but also of key
environmental parameters, as demonstrated in UV dosimetry.
This type of active spectrophotometry can significantly expand
the function in wearable device technologies, with additional
future possibilities for use within the body.

18. This work presents an indoor smart environment monitoring
system for safety applications.
It is based on custom wearable sensor nodes, connected to a static
wireless sensor networks.
Through a web application the network configuration can be
controlled and managed remotely, while receiving and
representing the information collected by the nodes.
The system has been developed for a hazardous gas environment,
but could be applied to a number of other safety applications or
in other areas such as the tracking of medical devices in a
hospital.

19. There are clear trade-offs between functionality, battery lifetime
and battery volume for wearable and implantable wireless-
biosensors which energy harvesting devices may be able to
overcome.
Reliable energy harvesting has now become a reality for
machine condition monitoring and is finding applications in
chemical process plants, refineries and water treatment works.
However, practical miniature devices that can harvest sufficient
energy from the human body to power a wireless bio-sensor are
still in their infancy.
This is useful for human energy harvesting in order to determine
power availability for harvester-powered body sensor networks.

20. The main competing technologies for energy harvesting from
the human body are inertial kinetic energy harvesting devices
and thermoelectric devices.
These devices are advantageous to some other types as they can
be hermetically sealed.
The fundamental limit to the power output of these devices is
compared as a function of generator volume when attached to a
human whilst walking and running.
A promising energy source for many current and future
applications is a ribbon-like device that could simultaneously
harvest and store energy.
Due to the high flexibility and weavable property, a
fabric/matrix made using these ribbons could be highly
beneficial for powering wearable electronics.

21. Unlike the approach of using two separate devices, here we report a
ribbon that integrates a solar cell and a supercapacitor.
The electrons generated by the solar cell are directly transferred
and stored on the reverse side of its electrode which in turn also
functions as an electrode for the supercapacitor.
When the flexible solar ribbon is illuminated with simulated solar
light, the supercapacitor holds an energy density of 1.15mWh/cm3
and a power density of 243mW/cm3.
Moreover, these ribbons are successfully woven into a fabric form.
Our all-solid-state ribbon unveils a highly flexible and portable
self-sufficient energy system with potential applications in
wearables, drones and electric vehicles (2).

22. It introduces active optoelectronic systems that function without batteries
In an completely wireless mode, with examples in thin, stretchable platforms designed for
multi-wavelength optical characterization of the skin.
Magnetic inductive coupling and near-field communication (NFC) schemes deliver power
to multicolored light-emitting diodes and extract digital data from integrated
photodetectors in ways
They are compatible with standard NFC-enabled platforms, such as smartphones and
tablet computers.
Examples in the monitoring of heart rate and temporal dynamics of arterial blood flow.
In quantifying tissue oxygenation and ultraviolet dosimetry
In performing four-color spectroscopic evaluation of the skin demonstrate the versatility
of these concepts.
The consequences have potential significance in both hospital care and at-home
diagnostics (4).
Devices require batteries and/or hard-wired
connections to enable operation.

24. Fig. 5. Wireless epidermal optoelectronic system with two pulsed LEDs and a single photodetector to monitor
peripheral vascular disease.
(A)Image of an epidermal wireless oximeter that includes a red LED, an IR LED, a photodiode, and associated
electronics all in a stretchable configuration mounted on a soft, black textile substrate coated with a low-modulus
silicone elastomer.
(B)Schematic illustration of the circuit of the device. An astable oscillator switches current between the two LEDs
to allow time-multiplexed measurement of both wavelengths with a single photodetector. The R1C1 and R2C2
tanks set the frequency of the oscillator. GND, ground.
(C)Images of the device operating during activation of the red LED (top) and the infrared LED (bottom).
(D)Image of the device mounted on the forearm. (Inset) Schematic illustration of the operating principle.
(E)Functional demonstration in a procedure that involves transient vein occlusion (gray box in the graph). An
inflating cuff on participant’s bicep temporarily occludes venous blood flow set to a pressure slightly below the
arterial pressure (50 mmHg).
(F)Magnified view of the red dashed box in (E).
(G and H) Measurements obtained by a commercial oximeter and an epidermal device, simultaneously recorded
from adjacent regions of the forearm. NIRS, NIR spectroscopy.

25. Wearable TEG Devices for Body Heat Harvesting TEG uses the
temperature difference between the body and the ambient
environment to produce electric power.
The heat from the body must be directed into the generator with
minimal loss.
The generator must be designed for maintaining a high
temperature differential across the thermoelectric material.
The generator must have a small weight and form factor for
comfort on the body.
The development of flexible TEGs for wearable applications was
a major innovation in body heating harvesting [8, 9, 10].

26. A flexible TEG provides better contact between the generator
and the skin, resulting in smaller thermal interface resistance
and, consequently, a larger temperature difference across the
TEG.
The power densities were in the range of sub-microwatt per
square centimeter, which was too small to power up sensors or
electronic circuits.
It has low performance [13].
For example, methods such as printing, spraying and molding
cannot be used to construct TEGs,
They result in low quality thermoelectric materials, impacting
the TEGs operational effectiveness.

27. Widely-used power sources, there are ongoing efforts to replace them with
permanent sources of energy, including research conducted by U.S. Army
Program Executive Office Soldier.
TEGs generate energy by harnessing body heat, producing consistent, reliable
electric power from the temperature difference between the body and the
ambient environment.
TEGs are now capable of powering low-power wearable electronic devices.
In the future, TEGs could be implemented as part of the U.S. Army Soldier
Power portfolio, [15] reducing warfighter weight load while simultaneously
enhancing device reliability.
TEGs also enable development of self-powered wearable health and
environmental monitoring sensors, which could provide uninterrupted
monitoring of warfighter health and safety conditions (13).

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