Page 23 - 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

related nanomaterials (e.g., CNT), whose properties can realized by this method [108]. Additionally,
be tuned by material doping and electric ield, have been bioluminescent molecules can be utilized as donors that
investigated [95, 96]. However, several challenges exist are excited upon binding speci ic target molecules,
for the practical implementation of THz‑band nanonet‑ promising for single molecular sensor networks within
works, such as the very limited communication range re‑ an IoBNT application [109, 110]. It is shown that the
sulting from high propagation losses due to molecular ab‑ limited range of FRET‑based nanocommunication can be
sorption, and low transmission power of resource‑limited extended to 10s of nanometers by multi‑step energy
transfer processes and multi‑excitation of donor
nanodevices. These challenges are being addressed
molecules [111, 112]. Lastly, an experimental study
by developing new very‑short‑pulse‑based modulation
demonstrated a high rate data transfer (250 kbps with a
schemes to overcome the limitations of THz transceivers −5
BER below 2 × 10 ) between luorescent‑dye
in terms of power [97, 98], and designing directional an‑
nanoantennas in a MIMO con iguration [113].
tennas and dynamic beamforming antenna arrays to over‑
come the propagation losses [99]. High density of BNTs
3.2 Bio‑Cyber and Nano‑Macro Interfaces
in envisioned IoBNT applications also pose challenges re‑
garding the use of the limited spectrum, which are ad‑
Most of the envisioned IoBNT applications require a
dressed by new medium access protocols for dense THz
bidirectional nano‑macro interface that can seamlessly
nanonetworks [100, 101].
connect the intrabody nanonetworks to the external
macroscale networks, and vice versa [114, 115]. Consi-
b) Acoustic Nanocommunication: Ultrasonic nanocom‑
dering that the MC is the most promising method for
munication has also been considered for connecting
intrabody IoBNT, the interface should be capable of
robotic BNTs inside the luidic environment of human
performing the conversion between biochemical signals
body due to its well‑known advantages over its RF coun‑ and other signal forms that can be easily processed and
terpart in underwater applications [102, 103, 104]. In communicated over conventional networks, such as
[102], it is shown that the best trade‑off between ef icient electromagnetic, electrical, and optical. Several
acoustic generation and attenuation is realized when the techniques are considered for enabling such a
acoustic frequency is between 10 MHz and 300 MHz for nano‑macro interface.
distances around 100 m. The authors also show that the
power harvested from ambient oxygen and glucose can be Electrical Interfaces
4 3.2.1
suf icient to support communication rates up to 10 bps.
In [105], the authors provide a testbed design for ultra‑
These are the devices that can transduce molecular sig‑
sonic intrabody communications with tissue‑mimicking
nals into electrical signals, and vice versa. Electrical
materials and as a result of extensive experiments, they
biosensors can readily serve the function of converting
report communication rates up to 700 kbps with a BER MC signals into electrical signals (see Section 3.1.1 for the
−6
less than 10 . use of electrical biosensors as MC receivers). The litera‑
An alternative approach proposed in [106] suggests the ture on biosensors is vast, and the irst practical demon‑
use of optoacoustic effect for the generation and detection stration of graphene bioFET‑based MC receiver shows
of ultrasonic waves via a laser and an optical resonator, promising results in terms of sensitivity, selectivity, and
respectively. It is shown that optoacoustic transduction reliability in electrical detection of MC signals [72]. How‑
ever, challenges posed by physiological conditions should
brings multiple advantages for ultrasonic nanocommuni‑
be overcome before employing biosensors as electrical in‑
cations, such as higher miniaturization, bandwidth and
terfaces, as detailed in [55, 13]. Conversion from electri‑
sensitivity over traditional piezoelectric/capacitive trans‑
cal signals into molecular signals is more challenging due
duction methods.
to the problem of maintaining continuous molecule
generation or supply. Existing electrical
c) FRET‑based Nanocommunication: Single molecular
stimuli‑responsive drug delivery systems rely on
BNTs are not capable of performing active communica‑
limited‑capacity reservoirs or polymer chains, e.g.,
tions, as in the case of MC and THz‑band EM communi‑
hydrogel, that can store certain types of molecules and
cations. On the other hand, external stimuli can supply
release them upon stimulation with a modulated rate.
the necessary means of information transfer. One such
However, these systems are typical irreversible, i.e., they
method is based on Fo ̈ rster Resonance Energy Transfer
cannot replenish their molecular stock unless they are
(FRET), which is a non‑radiative and high‑rate energy
replaced or reloaded externally [13]. In [116], a
transfer between luorescent molecules, such as luores‑
redox‑based technique is proposed and practically
cent proteins and quantum dots (QDs) [107]. The method demonstrated for interfacing biological and electronic
requires an external optical source for the initial excita‑ communication modalities, which can be used to
tion of donor molecules, which then transfer their connect a conventional wireless network with en‑
energy to ground‑state acceptor molecules in their gineered bacterial BNTs communicating via molecu‑
close proximity. Encoding information into the excited lar signals. The authors introduced the concept of
state of molecules, short‑range (5‑10 nm) but very electronically‑controlled biological local area network
high‑rate (on the order of Mbps) information transfer (BioLAN), which includes a biohybrid electrode that
© International Telecommunication Union, 2021 11