Biopotential Conducting Polymer Electrodes Design and Realization

for ECG Measurement

Marek Penhaker, Jan Polomik, Jan Kubicek and Vladimir Kasik

VSB – Technical University of Ostrava, FEECS, K450, 17. Listopadu 15, 708 33, Ostrava-Poruba, Czech Republic

Keywords: Alternative Biopotential Electrodes, Alternative Conductors, Polymer Electrodes, Polymer Conductors,

Conductive Polymer, ECG Measurement, ECG T-shirt.

Abstract: The paper deals with the design and consequent realization of the alternative non-metal bio-potential

electrodes and leads made from conductive polymers: polyaniline and polypyrrole. These alternative non-

metal biopotential electrodes and leads are intended for measurement of the ECG signal from chest by sensory

T-shirt. The electrodes and leads are fixed on the T-shirt for continuous measurement and monitoring ECG

signal. The alternative electrodes and leads were tested and compared against Ag/AgCl electrodes and

common (metal) electrodes.

1 INTRODUCTION

The ECG measurement has essential role in a clinical

practise. On the base of the ECG signal, it can be

discovered whether a patient suffers from a heart

disorder or heart disease which may not immediately

appear. Measuring of the whole 12 lead ECG may not

be for certain patients comfortable, can be stressful

and requires patient visit on a clinical workspace. The

future vision is allowing for measurement of ECG

signal from their home. Patient would wear specially

adjusted T-shirt with placed electrodes and leads.

ECG measurement would goes from their home

without presence of medical staff. Practically

commonly used bio-potential electrodes (Ag/AgCl)

has number of disadvantages as if necessity of

electro-conductive gel or paste, inability of their

using during CT examination and Magnetic

resonance, therefore, from the view of patient comfort

and effectivity, they are inappropriate for ECG

detection from T-shirt. (Le, 2016), (Vabiral 2011), )

(Wang, 2016), (Guttler, 2016) (Augustynek 2011)

For this reason, attention should be paid on new

materials which could allow for manufacturing

alternative bio-potential electrodes for user easy and

comfortable ECG measurement by T-shirt. (Cerny

2008, Cerny 2009) One of these materials is

conductive polymers. Polyaniline and polypyrrole

against other materials have a great advantage. Each

surface can be covered by these electrodes they do not

require presence of conductive gel or paste and

exhibit electric conductivity on the level of

semiconductors without any metal in their structure.

By this way, electrodes and leads made from

polyaniline and polypyrrole would be used even

during CT and Magnetic resonance examination.

(Peng, 2015), (Penhaker 2013, 2012) (Posada-

Quintero, 2016), (Chen, 2016), (Jekova, 2016)

(Marek 2015) (Penhaker 2011)

2 REALIZATION OF POLYMER

ELECTRODES

After applying standard polyaniline on fabric, this

fabric becomes so called polyaniline electrode (PANI

electrode). If that fabric is covered by globular

polypyrrole, it creates polypyrrole electrode (PPy

electrode).

2.1 Fabric Polymerisation by Standard

Polyaniline

Standard polyaniline was applied by the following

approach:

 For preparation of 100ml standard

polyaniline, 2.59 g 0.2M Aniline HCl and

5.71 g 0.25 APS was added.

134

Penhaker M., Polomik J., Kubicek J. and Kasik V.

Biopotential Conducting Polymer Electrodes Design and Realization for ECG Measurement.

DOI: 10.5220/0006150801340141

In Proceedings of the 10th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2017), pages 134-141

ISBN: 978-989-758-216-5

 Aniline HCl was given into bowl (50ml)

with distillated water. We had Aniline HCl

dissolved itself. This approach was repeated

also for APS.

 For ensuring even soaking solution into

whole fabric and prevention of their

movement, it was necessary to fabric stretch

and consequently fix on wooden frame.

 Fabric fixed on the wooden frame had to

souse several times into aniline HCl

solution.

 By this way, we let fabric in solution for 30

minutes.

 After taking 30 minutes, content with APS

solution was added to disinfection bowl.

 Fabric fixed on wooden frame was

prewashed by reaction mixture until that

time than the fabric reactionary colored.

Figure 1: Fabric prewashing fixed on wooden frame in the

reactionary mixture.

Figure 2: Cotton fabric covered by standard polyaniline.

Figure 3: Carbon fabric covered by standard polyaniline.

2.2 Electrical Resistance Measurement

of Polymer Fabric

Electrical resistance was measured on all polymers

fabrics with using of multi-meter ESCORT 3146A

and two measuring probes L4130. An electrical

resistance was measured in the distance 1, 10 and 16

cm between measuring probes. The resulting

resistance was determined as average resistance value

from these distances. Resistance values are

summarized in Tab. 1.

Table 1: Electrical resistance of all polymer fabrics.

Fabric Electrical resistance at 1 cm

distance\\ [Ω]

Cotton fabric (PANI) 11.10

Cotton fabric (PPY) 108

Carbon fabric (PANI) 51

2.3 Adjusting of PANI and PPy

Electrodes for ECG Measurement

In order to electrodes allow for easy fixing to chest

strap (optionally T-shirt), Velcro was used.

Electrodes are made by that way that same pieces

were cut from each fabric (with sewn Velcro) with

size 2x3 cm.

Figure 4: Obverse and reverse (a), PANI cotton electrodes

(b) and carbon electrodes PANI (c).

Biopotential Conducting Polymer Electrodes Design and Realization for ECG Measurement

135

2.4 Adjusting Chest Strap to ECG

Measurement

Strap consisted of upper and lower part intended for

ECG measurement was made from rubber bandage

ESMARCH with size 60x1250 mm. By this way

placing of electrodes for consequent one-lead ECG

measurement is reached.

Figure 5: Strap with PPy electrodes connected by

conductors.

2.5 Testing of Polymer Electrodes

For pilot testing PANI and PPy electrodes, one-lead

ECG device with bio-amplifier g.USB were used. The

measurement went according to measuring flow

chart. Three polymer electrodes of same kind were

fixed by Velcro on predetermined spots. Individual

polymer electrodes were connected to the bio-

amplifier by common wires. One-lead chest ECG on

chest was measured step by step with all polymer

electrodes (PANI – cotton electrodes, PANI – carbon

electrodes and PPy cotton electrodes).

Figure 6: Measurement of one-lead ECG on chest with

using of strap.

2.6 Signals and Results Testing

Measured ECG was recalculated on millivolts with

using MATLAB software (reflecting real values).

Figure 7: One-lead ECG measured by clip electrode

Ag/AgCl.

Figure 8: One-lead chest ECG measured by cotton PANI

electrodes.

Chest ECG from cotton electrodes (Fig. 8.) is affected

by movement artefact.

Figure 9: One-lead chest ECG measured by carbon

electrodes.

The movement artefact is present on all electrodes

(PANI, PPy). After connecting wires via crocodiles,

it went to badly fixing of crocodiles, polymer

electrodes movement during measurement. This

movement caused movement artefacts. For this

reason it was necessary to adjust connection between

BIODEVICES 2017 - 10th International Conference on Biomedical Electronics and Devices

136

conductor and polymer electrode by the way, so that

movement artefacts were eliminated. Crocodile

stabilization was performed by adhesive tape. One of

the advantages is easy reproducibility of

measurement.

Figure 10: One-lead chest ECG measured by cotton PPy

electrodes.

Figure 11: One-lead chest ECG measured by cotton PANI

electrodes after adjusting measurement chain.

Figure 12: One-lead chest ECG measured by carbon PANI

electrodes after adjusting measurement chain.

Individual ECG curves measured by all polymer

electrodes were without movement artefacts. Sticking

crocodiles to human body electrode movement

caused by conductor heaviness was prevented.

Figure 13: One-lead chest ECG measured by PPy electrodes

after adjusting measurement chain.

Since chest ECG was measured by polymer

electrodes and limb ECG was measured by clip

Ag/AgCl electrodes, it was not possible to compare

measured ECG values. They were not measured from

a same spot and measurement by polymer and

Ag/AgCl electrodes did not go in the same time, thus

individual ECG signals can be different in pulse

having significant influence on ECG signal.

2.7 Summarization of Chest and Limbs

Measurement

On the base of the ECG curves is obvious if we ensure

sufficient pressure (contact) of polymer electrode

with skin, ECG can be measured with accuracy

comparable as if Ag/AgCl electrodes. This fact is

proved by correlation coefficient (Tab. 2.) from limbs

measurement where we ensured sufficient contact

with skin.

Table 2: Correlation coefficients comparison for chest and

limbs measurement.

Polymer

electrode

Correlation

coefficient - chest

Correlation

coefficient -

limbs

Cotton PANI

0.9332 0.9944

Cotton PPy

0.9515 0.9935

Carbon PANI

0.9349 0.9835

Correlation coefficients for cotton PANI and PPy

electrodes were around 0.99. These correlation

coefficients are generally much greater than for chest

measurement where the highest correlation

coefficient (0.95) was achieved on cotton PPy

electrode.

Biopotential Conducting Polymer Electrodes Design and Realization for ECG Measurement

137

3 DESIGN AND REALIZATION

OF T-SHIRT FOR ECG

MEASURING

A reliable T-shirt for ECG measurement should be

slim and copy shape of human body, so that pressure

of polymer electrodes to body would increase. For

achieving required contact polymer electrode with

human body, bandages were sewn to given spots of

T-shirt (upper part of chest and stomach area).

PPy cotton electrode (2x2 cm) was fixed to

Velcro. PANI carbon conductor with length 60 cm

isolated by tubule was placed between electrode and

Velcro and firmly connected with electrode. Velcro

was used for easy undoing electrodes from bandage.

Figure 14: T-shirt with stich bandage and placed polymer

electrodes.

3.1 Prototype T-shirt Testing

Three PPy electrodes with isolated PANI conductors

were fixed by Velcro on defined T-shirt spots. Close

to PPy electrodes, disposable stick AG/AgCl was

stick which was connected via common wires with

second one-lead ECG. Both ECG devices were

connected to same A/D converter which was

connected with PC. ECG in stable position and during

selected movements (run, gait and knee-bend) was

measured by such measuring chain. Run and gait

simulation were simulated on one spot due to short

conductor length.

Figure 15: Measuring chain for measuring one-lead ECG

from T-shirt by PPy cotton electrodes with PANI carbon

conductors and in the same time by stick Ag/AgCl

electrodes (placed on the human body) with common wires.

3.2 Measurement Results

For objective comparison of two measured and

recalculated ECG curves. Such time interval was

selected, so that it contains 10 ECG curves detected

in the same time as if PPy cotton electrodes with

PANI carbon conductors. From these extracted ECG

curves, their difference and correlation coefficient

was calculated. Maximum, minimum, average value

and dispersion of calculated difference were

calculated as well. In the case of movement

simulation, recalculated ECG curves were drawn to

graphs.

ECG curves in sitting position measured in the

same time by PPy cotton electrodes with carbon

PANI conductors and stick Ag/AgCl electrodes

(placed on human body) and common wires and

graph of the calculated difference of both extracted

and recalculated are shown on Fig. 16. ECG curve

measured by Ag/AgCl electrodes with common wires

is shifted about +1.2 mV, so that do not cover itself

with measured ECG signal by PPy cotton electrodes

with PANI carbon conductors.

Figure 16: ECG curve in sitting position, common Ag/AgCl

electrodes (blue), PPy cotton electrodes (red) and their

difference (violet).

BIODEVICES 2017 - 10th International Conference on Biomedical Electronics and Devices

138

Figure 17: Curve of ECG signals difference.

The statistical results of ECG measured

simultaneously from T-shirt by PPy cotton electrodes

with PANI carbon conductors and stick Ag/AgCl

electrodes (placed on body) with common conductors

are summarized into Tab. 3.

Table 3: Statistical parameters of sitting position by PPy

cotton electrodes with PANI carbon conductors and stick

Ag/AgCl electrodes with common conductors.

Calculated parameter Parameter value

Maximum of difference

0.15 mV

Minimum of difference

-0.14 mV

Average value of difference

-0.031 mV

Dispersion of difference

0.0021 mV

Correlation coefficient

0.96

4 FINAL CONCEPT OF T-SHIRT

FOR ECG MEASUREMENT

The first T-shirt prototype did not allow for one-lead

ECG measurement during exercising given activities

representing common physic load. One of the causes

could have been moving connection of polymer

conductors and crocodiles. The second cause could

have been decreased contact of electrode fixed to

lower bandage placed to lower T-shirt part. On the

base of these circumstances, it was approached to

design of final T-shirt prototype for ECG

measurement with directly placed Velcro on T-shirt

without using of bandages. Velcro was placed close

to right and left breast and to the area between chest

and hip-bone. Connection of PPy cotton electrodes

and PANI carbon conductors were same as in the

previous case, only there is the difference of isolation.

Electrical isolation was performed by electrician

tubing. The design of final T-shirt prototype for ECG

measurement is depicted on the Fig. 17.

Figure 18: Final design of T-shirt prototype for ECG

measurement.

5 CONCLUSIONS

The main aim of our research was design and

practical implementation of the polymer bio-potential

electrodes including their leads with using conductive

polymers of polyaniline or polypyrrole. Final output

is the T-shirt prototype intended for continual

detection and monitoring of ECG signal. Electrodes

were manufactured from cotton fabric with

polyaniline, cotton fabric with polypyrrole and

carbon fabric with polyaniline. All three types of

electrodes were compared from the view of detected

and transmitted signal quality against common

Ag/AgCl electrodes with electro-conductive gel. All

electrodes allowed for ECG measurement from both

chest and limbs. The best results from the view of

quality and amplitude strength were achieved by PPy

cotton electrodes.

On the base of the polymer electrodes and

conductors testing it was approached to realization of

polymer electrode and polymer conductor connection

and their placing on the T-shirt. The best results

during testing were achieved by PPy cotton electrodes

and PANI carbon conductors, therefore, the most

optimal combination of these electrodes was selected

for ECG measurement by T-shirt.

Our research contributes to manufacturing of new

non-metal polymer electrodes and conductors. ECG

measurement from T-shirt was successfully tested in

lab conditions. We achieved good results (conformity

96.7%) on sitting position. On the other hand, ECG

results during performing of predefined exercises we

achieved results affected by artefacts. The significant

movement artefact could have been caused by

technological fixing of polymer electrodes and

connecting polymer conductors with lead conductors

Biopotential Conducting Polymer Electrodes Design and Realization for ECG Measurement

139

of ECG device. The possible direction of future

polymer work could be testing on CT (Computer

Tomography) and MRI (Magnetic resonance), multi-

lead T-shirt realization and ensuring of resistance

against movement artefacts.

ACKNOWLEDGEMENTS

This article has been supported by financial support

of TA ČR ,PRE SEED Fund of VSB-Technical

univerzity of Ostrava/TG01010137. The work and the

contributions were supported by the project

SV4506631/2101 'Biomedicínské inženýrské

systémy XII'.

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