A Modular BLE-Based Body Area Network Embedded into a Smart

Garment for Rescuers Real-Time Monitoring in

Emergency Scenarios

Giulia Sedda

, Giulia Baldazzi

, Salvatore Spanu

, Antonello Mascia

, Andrea Spanu

Piero Cosseddu

, Annalisa Bonfiglio

and Danilo Pani

Department of Electrical and Electronic Engineering (DIEE), University of Cagliari, Cagliari, Italy

Keywords: Body Area Network, BLE, First Responders, Wearable Sensors, Smart Garment.

Abstract: In this work, we present a prototype of a smart technical underwear for first responders involved in search-

and-rescue operations, to be worn under the rescuer’s professional uniform. Polymer-based electrodes able to

detect ECG and EMG signals, and organic transistor for joint angles estimation are embedded into the smart

garment. The technical underwear implements a body sensor network of BLE nodes able to acquire, process

in real-time and transmit electrophysiological and biomechanical data from the sensors to a custom Android

app on the rescuer’s smartphone. The app geolocates the data by using the information of the GPS integrated

into the smartphone and sends them to the control center for remote monitoring. The system features high

modularity, as the rescuer can adopt a subset of sensors depending on the specific operative context, without

any app configuration.

1 INTRODUCTION

First responders involved in difficult search-and-

rescue operations are subject to hazardous conditions,

and it is critical to take care of their safety and health

status during the operations. The development of

smart garments with physiological and

biomechanical sensing capabilities, to be integrated in

a broader monitoring system, is then of paramount

importance for their safety. In this context, wearable

technologies for vital signs monitoring represent a

great opportunity to obtain unobtrusive sensing

allowing free movement and operation.

Recently, various sensorized technical clothing

for rescuers have been designed, such as the system

developed in the ProeTEX (Protection e-Textiles:

Micro-Nano-Structured fiber systems for

Emergency-Disaster Wear) European project, which

integrates wearable and portable sensors, in order to

detect both parameters representing the health status

of the firefighter and environmental variables

https://orcid.org/0000-0002-9662-7697

https://orcid.org/0000-0003-1275-4961

https://orcid.org/0000-0002-2600-8241

https://orcid.org/0000-0002-4185-7225

(Curone et al. 2010). The sensing nodes, both custom

and commercial, devoted to assessing the health

status of the emergency operator, are distributed in an

internal garment and provide the heart rate, the

breathing rate, the body temperature and the blood

oxygen saturation. An outer garment assesses the

operator activity state and monitors the surrounding

environment, by estimating the operator position,

activity, and posture, and measuring the external

temperature, the presence of toxic gases, and the heat

flux passing through the garments. The internal

garment is a T-shirt directly in contact with the user

skin; to maximize the user comfort, textile-based

and/or textile-compatible technologies have been

employed. Both sensors and electrodes are connected

to the electronic modules through textile-conductive

cables integrated in the shirt. All the data are

transmitted remotely to the operation manager in real-

time through the Wi-Fi network.

In 2014, Salim et al. designed a sensorized T-shirt

to monitor physiological parameters such as skin

https://orcid.org/0000-0003-0331-7516

https://orcid.org/0000-0003-4896-504X

https://orcid.org/0000-0001-7866-4526

https://orcid.org/0000-0003-1924-0875

Sedda, G., Baldazzi, G., Spanu, S., Mascia, A., Spanu, A., Cosseddu, P., Bonﬁglio, A. and Pani, D.

A Modular BLE-Based Body Area Network Embedded into a Smart Garment for Rescuers Real-Time Monitoring in Emergency Scenarios.

DOI: 10.5220/0011778100003414

In Proceedings of the 16th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2023) - Volume 1: BIODEVICES, pages 177-181

ISBN: 978-989-758-631-6; ISSN: 2184-4305

 2023 by SCITEPRESS – Science and Technology Publications, Lda. Under CC license (CC BY-NC-ND 4.0)

177

temperature, heart rate, heat flux, and ultraviolet

exposure, in order to assess the firefighter's thermal

status and alert workers regarding the heat exhaustion

while operating in hot industrial environments.

Sensor data and alerts are sent wirelessly (XBee

series-1 radio) in real-time to the wearer, by using a

phone App, and to the remote center.

Afterwards, a smart T-shirt made out of Nomex

fabrics, which has inherent flame-resistant and very

low heat-conductance properties, was designed to

detect the mental stress of the firefighters. The smart

garment monitors their physiological signals (i.e., the

heart rate) and the environmental conditions

(temperature and humidity) and processes this

information with a machine learning algorithm

(Sandulescu et al. 2015). The system also integrates

movement sensors and a microphone for team

communication, whose features are elaborated for

stress monitoring of rescuers. Wires connecting to the

data acquisition and processing unit are woven in the

garment. Data are sent remotely in real-time by using

the ZigBee protocol.

As part of the H2020 Search & Rescue European

Project (https://search-and-re-rescue.eu/), we

designed, developed, and tested on the field a smart

underwear implementing a BLE-based modular

wearable system for rescuers operating in critical

emergency contexts, such as searching people trapped

under the rubble. The system is able to collect

physiological and biomechanical parameters

measured by custom-designed wireless sensing nodes

acquiring data (ECG, EMG, and strain) from as many

sensors embedded in the smart underwear. Each node

sends the edge-processed data to a wearable hub,

represented by a smartphone, which is in charge of

local visualization and real-time transmission to the

operational control center.

2 SYSTEM ARCHITECTURE

The developed smart underwear has been designed to

be worn under the rescuer’s uniform, allowing

monitoring the ECG, EMG, and knee joint angle of

the first responder during the search and rescue

operations. It is composed of a T-shirt and leggings

made of a highly breathable, stretchable, resistant,

and comfortable polyester fabric.

2.1 Sensing Elements

As shown in Figure 1, the garments are functionalized

in the targeted areas using a biocompatible

conductive ink based on poly(3,4-

ethylenedioxythiophene) polystyrene sulfonate

(PEDOT:PSS) (Tsukada et al. 2012, Tseghai et al.

2020), to form electrodes able to detect cardiac and

muscle biopotentials (Guo et al. 2016, Sinha et al.

2017, Pani et al. 2018, Achilli et al. 2018, Spanu et al.

2021). Two ECG electrodes are positioned on the

chest, symmetrically with respect to the sagittal line,

to detect the ECG according to the lead I direction. A

further electrode on the back, approximately at the

same height, provides the signal ground for this

recording (Figure 1 - light blue circles - and Figure

2A). Experimentally, after carrying out several tests,

this configuration of the electrodes proved to be the

best for guaranteeing adhesion of the electrode and

the acquisition of a good signal (data not shown). A

couple of EMG electrodes is placed on the upper leg,

to detect the activity of the vastus medialis, with a

ground electrode over the knee (Figure 1 - red circles

– and Figure 2A, 2D). A second couple of EMG

electrodes is positioned on the gastrocnemius

medialis, with the ground electrode over the

shinbone. Similar to ECG, various possibilities were

tested for the configuration of the electrodes for

EMG, and the one chosen proved to be the best. All

the electrodes were patterned directly on the finished

garment using a customized screen-printing

technique, as already reported in Spanu et al. (2021).

The employed technique allowed to obtain perfectly

functional electrodes even upon a sustained stretch of

the garment.

Figure 1: Overview of the smart underwear.

Biopotentials from the electrodes are read by

custom-developed, low-power, low-cost, small

wireless nodes (Figure 1, blue rectangles). In

particular, the nodes embed the TI’s ADS1292

module, a 24-bit, 2-channel ADC with an integrated

analog front-end for electrophysiological signals

(ECG, EMG). The connection between the wireless

node and the electrodes is made up of conductive steel

threads sewn directly on the underwear (see both

Figure 1 and Figures 2A, 2D). As the performance of

the electrodes depends on their coupling with the

BIODEVICES 2023 - 16th International Conference on Biomedical Electronics and Devices

178

skin, which must be stable and characterized by low

impedance, the electrodes were firmly attached on the

skin by using elastic bands able to guarantee a

uniform and constant pressure over the skin (Figure

2D).

Lastly, an organic semiconductor-based strain

sensor is placed over the popliteal fossa (Figure 1, the

green vertical strip), that is able to dynamically

change its resistance according to the angular

extension of the joint (Taroni et al. 2018, Sezen-

Edmonds et al. 2019). It is a three-terminal device,

namely thin-film transistors (TFT), whose sensitivity

can be tuned and amplified by means of the gate field,

and that can be incorporated into cotton garments for

measuring joint movements (Lai et al. 2019). In this

case, the wireless node is directly attached to the

sensors without any conductive yarn.

Figure 2: A: Front view of the smart underwear, with ECG

and EMG electrodes for vastus medialis muscle; B:

Custom-developed wireless node; C: Neoprene pocket

housing the electronic node. Velcro stripes allow the pocket

to be easily attached to the garment. D: Back view of the

smart underwear, with detail on both the strain sensor on

the left, and EMG electrodes for gastrocnemius medialis on

the right.

2.2 Wireless Nodes

The wireless nodes support both acquisition and basic

edge-processing features, and are housed in small

neoprene pockets along with their battery, as shown

in Figure 2C. They are based on a Texas Instrument

CC2640R2F microcontroller, integrated in a

convenient system-on-module (Figure 2B). This

wireless microcontroller features an ARM Cortex-

M3 processor (32 bit), running at 48 MHz, with

275 kB of non-volatile memory, ultra-low power

sensor controller, and several peripheral modules

(e.g. general-purpose timer modules, 12-bit ADC,

UART, I2C, I2S, SSI, Real-Time Clock, and others).

In particular, the ultra-low power sensor controller

can interface with external sensors and collect

analogue and digital data independently, while the

rest of the system is in sleep mode. Lithium-polymer

batteries (720 mAh, 3.7V) have been selected by

overestimating the duration of the typical emergency

interventions, as they can provide supply for a week

at full strength.

The estimated power consumption

of the wireless node is about 15mW.

The CC2640R2F is provided with a radio

frequency module, implementing a 2.4 GHz

transceiver compatible with Bluetooth low-energy

(BLE) 5.1 and earlier low-energy specifications. It is

characterized by excellent receiver sensitivity (–97

dBm for BLE), selectivity and blocking performance.

This is also suitable for systems targeting compliance

with worldwide radio frequency regulations, i.e.,

ETSI EN 300 328 (Europe), EN 300 440 Class 2

(Europe), FCC CFR47 Part 15 (US), or ARIB STD-

T66 (Japan).

2.3 A BLE-Based Body Area Network

Each sensor is provided with a dedicated BLE node,

to foster modularity and the possibility to equip the

first responder only with the useful sensors for the

given scenario, avoiding over-connected and useless

smart garments that could hamper the mobility and,

consequently, the field operation.

Each wireless node is able to detect a single-

channel signal, which is edge-pre-processed to extract

the heart rate from the ECG signal, the maximum

voluntary contraction of the EMG signal, and the

angular extension of the knee joint. Raw data and key

features (such as the heart rate) are sent to the

rescuer’s smartphone in real-time, by using custom-

defined GATT characteristics. Data rate is signal-

dependent: as such, the ECG signal is sampled and

sent at 250 Hz; the EMG signal is sampled at 250 Hz,

whereas its envelope is edge-computed and sent at

50 Hz; joint angles are sampled at 10 Hz and their

average value is sent at 1 Hz. A custom Android app

was designed to collect the data from the different

wireless nodes (see Figure 3). On the smartphone, by

using the information of the integrated GPS module,

data are geolocated and sent to the remote web server,

every five seconds in independent chunks, through

Wi-Fi or cellular network.

The app is able to interact with Apache Kafka, a

broker for streaming processing based on a

distributed data storage, which receives the data in

JSON format in real-time every 5 s. Depending on the

sensor type, the data file comprises different fields;

the size of the field that contains the signal depends

on the sampling frequency of the data.

A Modular BLE-Based Body Area Network Embedded into a Smart Garment for Rescuers Real-Time Monitoring in Emergency Scenarios

179

Figure 3: Overview of the system architecture.

The application has a very simple interface

(Figure 4), which provides information on the sensors

connected to the application, and therefore in use. In

addition, the app allows real-time display of some

characteristics of the Global Navigation Satellite

Systems (GNSS) location, including latitude,

longitude and altitude coordinates, detected through

the GPS sensor embedded in the smartphone. Finally,

it shows the status of communication with the server

(SERVER RESPONSE: OK/NO NETWORK), and

the total number of packets sent and queued

(therefore not yet consumed by the server) for each of

the connected nodes.

Figure 4: The Search & Rescue Android App sends the data

to the web server in real-time.

3 DISCUSSION

The smart underwear prototype presented in this work

differs from similar solutions described in the

literature for several aspects. In fact, it consists of

both a T-shirt and a leggings, compared to Curone et

al. 2010, Salim et al. 2014, Sandulescu et al. 2015,

allowing for monitoring the muscle contraction at the

level of the lower limb and the angle of the knee joint,

which give indications on the rescuer's activity.

Furthermore, the application of organic

semiconductor sensors, such as electrodes for

electrophysiological measurements and the strain

sensor for detecting knee angle, is completely new in

the search and rescue field, where it can be widely

used for monitoring the physical and health

conditions of the first responder in a totally non-

invasive way, with innovative and low-cost materials

and through technologies that have shown good

performance compared to the gold standard.

In addition, the position of the nodes on the

underwear is independent of that of the actual sensors,

therefore it can easily be modified to meet the specific

needs of the rescuer.

Another important aspect concerns the size of the

node, which is miniaturized and with low power

consumption compared to the solutions found in the

literature: for example, for the same battery capacity

(1200 mAh), each node of our prototype can work

continuously for days (up to a week) with all the

sensors connected, while the smart solution proposed

by Salim et al. 2014 can work continuously up to 5

hours without the GPS connected.

4 CONCLUSIONS

At present, the smart underwear was successfully

tested in the first two demonstrative use cases on the

field envisaged in the project.

Currently, up to four sensors can be present on the

underwear to sense and transmit the physiological and

biomechanical data of the rescuer. The functionalities

of both the smart underwear and the custom Android

app are being extended to include the acquisition of

signals coming from other types of sensors, also

eventually integrated in the external uniform.

ACKNOWLEDGEMENTS

The authors acknowledge funding from the European

Union’s Horizon 2020 research and innovation

programme under grant agreement No. 882897–

Search&Rescue project.

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