Page 25 - ITU Journal Future and evolving technologies Volume 2 (2021), Issue 3 – Internet of Bio-Nano Things for health applications

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 3

3.3 Energy Harvesting, Power Transfer, and [138, 143], can be exploited to power the BNTs in an intra‑
Energy Ef iciency body IoBNT. Among the potential EH mechanisms for in‑
trabody IoBNT, mechanical EH has attracted the most in‑
Supply, storage and ef icient use of energy is one of the terest. Research in this ield has gained momentum with
most crucial challenges towards realizing the envisioned the use of lexible piezoelectric nanomaterials, such as
IoBNT applications. The energy challenge is currently be‑ ZnO nanowires and lead zirconate titanate (PZT), in nano‑
ing addressed through the development of energy har‑ generators, enabling energy harvesting from natural and
vesting (EH) and wireless power transfer (WPT) tech‑ icial vibrations with frequencies ranging from very
niques to continuously power BNTs, the development of low frequencies (< 1 Hz) up to several kHz [144, 145].
high‑capacity energy storage devices at micro/nanoscale,
and the design of low‑complexity and energy‑ef icient Wireless Power Transfer
3.3.2
communication methods for IoBNT.
For BNTs based on engineered cells, the challenge of Another way of powering BNTs and IoBNT applications
energy management is relatively straightforward, as can be WPT from external sources. WPT has seen sig‑
living cells have been evolved over billions of years to ni icant advances in recent years due to increasing need
make the most ef icient use of biochemical energy for for powering battery‑less IoT devices as well as wea-
realizing vital functionalities. Nonetheless, energy rable and implantable devices. Various forms of WPT
budget requirements of engineered cells may be have been considered for powering medical implants
extended with the introduction of new computation and [146, 147]. For example, near‑ ield resonant inductive
communication functionalities that are demanded by coupling (NRIC)‑based WPT, the oldest WPT technique,
complex IoBNT applications. On the other hand, there has been in use for widely‑used implants, such as
are only a few studies that consider the overall energy cochlear implants [148, 149]. Other techniques include
requirements of MC for only very simple scenarios [133, ield capaci‑ tive coupling, mid ield and far‑ ield
134]. The problem is, of course, more challenging for EM‑based WPT, and acoustic WPT. Power transfer via
arti icial BNTs, such as those that are made up of ield capacitive and inductive coupling, however, is
nanomaterials and missing an inherited metabolism for only ef icient for dis‑ tances on the order of transmitting
energy management. and receiving device sizes, and for the right alignment
of devices, and there‑ fore, might not be suitable for
3.3.1 Energy Harvesting powering micro/nanoscale BNTs [148]. On the other
hand, radiative mid‑ ield and far‑ ield EM‑based WPTs
Leaving aside the continuous efforts to reduce the com‑ can have looser restrictions depending on the frequency
plexity of communication methods for IoBNT, such as of EM waves.
modulation and detection techniques [13], in the hope Recent research on mm‑wave and THz rectennas suggests
of increasing energy iciency, the most promising so‑ the use of high‑frequency EM WPT techniques to power
lution to enable self‑sustaining IoBNT is the integration BNTs [150]. However, for intrabody applications, the
of EH modalities into BNTs. EH has recently received higher absorption with increasing frequency and power
tremendous research interest partly due to the energy restrictions should be taken into account. Nonetheless,
requirements set by emerging applications of IoT and simultaneous wireless information and power transfer
IoE. Depending on the application environment and de‑ techniques (SWIPT) utilizing THz‑band have been inves‑
vice architectures, various natural energy sources have
tigated for EM nanonetworks [151, 152]. Similar SWIPT
been considered for harvest by IoT devices [135, 136].
applications have been considered for MC, where the re‑
For example, solar energy, vibration sources, electroma-
ceiving BNTs use the received molecules for both deco-
gnetic sources, e.g., ambient RF EM waves, and
ding the information and energy harvesting [153,
metabolic sources have been deemed feasible for
154]. There are also applications of acoustic WPT for
harvesting [137]. Concerning the intrabody and body
biomedical implants using external ultrasonic devices
area applications, human body stands as a vast source
[155, 156]. Although not implemented yet, ultrasonic
of energy in the form of mechanical vibrations resulting
EH has been also considered for powering BNTs with
from body movements, respiration, heartbeat, and blood
piezoelectric transducers [157, 158, 125].
low in vessels, thermal energy resulting from body heat,
An interesting research direction in parallel with the
and biochemical energy resulting from metabolic
wider IoE vision is towards hybrid EH systems that can
reactions and physiological processes [138]. Literature
now includes a multitude of successful applications of exploit multiple energy sources. Prototypes have been
human body EH to power miniature biomedical implemented for ZnO nanowire‑based hybrid cells for
devices and implants, such as thermoelectric EH from concurrent harvesting of solar and mechanical energies
body heat for wearable devices [139], vibrational EH [159], and piezoelectric PVDF‑nano iber NG based hybrid
from heartbeats [140] and respiratory movements cells for biomechanical and biochemical EH from bodily
[141] to power pacemakers, as well as biochemical EH luids [160]. A hybrid EH architecture is also proposed
from human perspiration [142]. These together with for IoE comprising modules for EH from light, mechanical,
EH from chemical reactions within the body, such as thermal, and EM sources [161]. The same hybrid archi‑
glucose uptake, lactate release, and pH variations tectures could be considered for IoBNT as well to main‑

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