IEEE Systems, Man and Cybernetics Magazine - July 2020 - 42

Earset Packaging
e-AR Sensor

StO2 Sensor
Packaging
NIRS StO2 Sensor
Smart Tattoos

Bacteria
SERS Gold Pattern
Optical Fiber
Electronics
Paper-Based Fluidics
Fluidic
Sensors

have been developed to link MEMS sensor
readings to various pathologies, physical
fitness, and athletic performance. One
example is the bioinspired ear-worn activity recognition (e-AR) sensor (Figure 2). It
can mimic the vestibular system and capture shock waves generated by groundreaction forces (GRFs). From the latter,
plantar pressures can be deduced for gait
analysis [21], which can be used postoperatively for rehabilitation.
Metabolic and physical changes will
alter tissue's electrical properties and
impedance (bioimpedance) [2]. -T issue
ischemia leads to edema because water
shifts toward the intracellular space when
cell-membrane pumps fail, changing the
low- and high-frequency tissue-impedance
spectra. Similarly, cancer tissues with
increased vascularization lead to impedance changes. Electrical bioimpedance
biopsies are applicable across the perioperative-care pathway (Figure 1). Sensor
designs must conform to particular applications and be governed by geometrical
optimization to tailor the devices' electricfield distribution [12].

Electrochemical Sensors
Electrochemical sensors have attracted
extensive attention for the detection of
biomarkers, metabolites, trace metals,
Chemical-Sensing
and various ions across the perioperaElectrodes
tive-care pathway [2], [14], [22], due to
Impedance
their low power consumption and cost,
Spectroscopy
miniaturization, and real-time sensing
Electrodes
capabilities [2]. The pH and glucose sensors are the most common, typically with
Figure 2. Tethered, wearable, and implantable devices and
the former being a potentiometric and the
embodiments, including the ear-worn sensor from [21], wearable wireless
latter an amperometric sensor. The latest
NIRS sensor from [15], schematic example of an epidermal smartdevelopments in the use of nanomaterials
tattoo wireless sensor, optical-fiber-based surface-enhanced Raman
spectroscopy (SERS) sensor from [27], [54], sweat-sampling microfluidic
have led to sensors with enhanced perforwearable wireless patch from [22], inductively powered implantable
mance [23]. However, there are still issues
device with dedicated application specific integrated circuits (ASICs),
that need to be resolved related to longand ring and patch sensing platforms for bioimpedance, amperometric,
term continuous monitoring and stability,
and potentiometric sensing from [14]. e-AR: ear-worn activity recognition.
sampling, and calibration. We have developed a range of electrochemical sensors,
including
lactate
[22]; pH; sodium ion ( Na +) potassium
surgical incisions. Pressure and strain are two physical
parameters employed to monitor mechanical motions. The
ion (K +) [14], [24]; and glucose [25].
former is particularly useful for monitoring blood dynamics and the latter for pre- and postoperative orthopedic
Optical Sensors
applications. Extensive research into wearables for preSpectroscopic analysis based on light-tissue/biofluid interand postoperative care has focused on accelerometers,
action is another powerful sensing technique, typically leadgyroscopes, and magnetometers for monitoring motion.
ing to the highest sensitivities and accuracies. Such sensors
Many commercial devices incorporate such devices, which
have been confined to the pre- and postoperative phases
have a wide availability and low cost. Numerous models
because of their bulky instrumentation. New developments
ASIC Chip
Induction Coil

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IEEE SYSTEMS, MAN, & CYBERNETICS MAGAZINE Ju ly 2020
IEEE Systems, Man and Cybernetics Magazine - July 2020

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