Instrumentation & Measurement Magazine 24-5 - 41

Optical Fiber-Integrated Smart
Structures: Towards Transparent
Devices for Healthcare 4.0
Arnaldo Leal-Junior and Carlos Marques
T
he whole world experienced in the last decades a
continuous change in the age pyramid related to the
population aging, where there is an increase in the elderly
population (over 65 years) when compared with other
age groups [1]. Such demographic change is not essentially an
issue, since it demonstrates that the life expectancy is increasing,
directly related to many advances in medicine, public
health and biotechnology as well as social and economic developments
that allow access for the general population to
health treatments [1]. The population aging in conjunction
with chronic diseases, where some of them are also age-related,
leads to some clinical conditions that can affect human
health such as osteoarthritis, rheumatoid arthritis, Alzheimer's
disease, Parkinson's disease and weakness of the skeletal
muscles [2]. These clinical conditions can lead to different
types of disabilities, and the most common type is locomotion
impairment, which occurs with nearly 14% of the world population
[3] and represents around 1 billion people. As locomotor
impairment harms work performance, activities of daily living
and independence in the community, there is a necessity
for continuous treatment of the different conditions that result
in locomotor impairments.
This scenario pushed the boundaries for novel treatments
and methods for continuous monitoring of patients, where
the latter has been motivated by the many developments
in internet of things (IoT) and resulted in the development
of smart wearable devices and environments that enable
the remote and continuous monitoring of the patients [4].
Such continuous monitoring results in the possibility of telemedicine
for remote diagnosis, transportation in case of
emergencies, and monitoring patient's health condition. In
addition, it results in economic and social benefits due to the
reduction in the treatment cost and lower hospitalization
(and other clinical facilities) [5], where the latter is particularly
important, since many regions report shortage of
physiotherapists. The therapist availability is about 5 physiotherapists
per 10000 people in high-income countries, and
it is worth noting that this availability is even lower in lowincome
countries [1].
August 2021
These new developments, in conjunction with other features
related to machine learning, deep learning and big data
analysis as well as the developments in low latency communications
of 5G, have resulted in smart healthcare networks
[6]. Recently, the term Healthcare 4.0 has been used to address
several novel applications in healthcare including remote
healthcare, ambient-assisted living, clinical healthcare management
as well as remote assistance [7]. To that extent, many
enabling technologies were proposed using smartphones
[8] and sensor networks [9]. As one of the emerging sensing
technologies, optical fiber sensors can be multiplexed into
multiple sensors in a single fiber cable, where their flexibility
enables them to be embedded in clothing and offer flexible environments
[10]. This paper is not an exhaustive review of the
literature but includes a survey of recently published works
of the side-coupled multiplexing technique for intensity variation-based
sensors that presents the foundation for low cost
multiplexed sensors based on optical fibers integrated in different
structures for Healthcare 4.0.
Introduction to Optical Fiber Sensing
Technologies
Flexible sensors, fabrics and smart textiles have been proposed
in recent years for wearable monitoring applications of many
parameters, such as oximetry, heart rate, respiration rate and
movement analysis [11]. Such approach has the advantages of
compactness, light weight, offering wireless connection and
requiring low energy that are well-aligned with IoT systems
[4]. Furthermore, the requirements of a smart textile include
the ease of removal and installation as well as flexibility as it
cannot inhibit the natural movements of the users.
Despite the advances in electronic sensors, including
flexible electronics in different substrates that allow the development
of a few approaches in smart textiles, optical fiber
sensors are increasingly employed in a multitude of applications
that range from environmental monitoring to medical
devices [12]. The small dimensions and weight of optical fibers
as well as their electromagnetic and galvanic isolation motivate
such widespread of these sensors, including wearable
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