A Thermochromic Ink Heater-cooler Color Change System for

Medical Blood Simulation

Mohammad Noorizadeh, Abdullah Alsalemi, Yahya Alhomsi, Faycal Bensaali and Nader Meskin

Department of Electrical Engineering, Qatar University, Doha, Qatar

Keywords: Simulation-based Training (SBT), Extracorporeal Membrane Oxygenation (ECMO), Blood Oxygenation,

Thermochromism, High-fidelity Simulation, Temperature Control.

Abstract: Extracorporeal membrane oxygenation (ECMO) is a modified form of CPB that supports intensive care

patients’ vital functions during recovery from cardiac or pulmonary trauma. ECMO, although lifesaving, is

vulnerable to a plethora of mechanical complications which can cause mortality. This is why developing

advanced training systems is of crucial importance. In this paper, as part of an ECMO simulator for training

management, a novel thermochromic heater-cooler system is presented. The need of such contribution arises

from the lack of high-realism blood simulation methodologies Hence, developed upon thermochromic ink,

cost-effective blood simulation is achieved by temperature adjustment, simulating oxygenation and

hypoxemia. The system has been developed as a prototype with successful and reversible transitions between

dark and bright red blood color. After addressing the limitations, the heater-cooler will be integrated with the

ECMO simulator, allowing unpreceded cost-efficient simulation possibilities.

1 INTRODUCTION

Cardiopulmonary bypass (CPB) is technique that is

employed to take over a patient’s blood circulation

and oxygenation functions, and is commonly used

during open-heart surgery; allowing surgeons to

easily operate on a beat-less heart (What Is

Cardiopulmonary Bypass?, 2004). Extracorporeal

membrane oxygenation (ECMO) is a modified form

of CPB that supports intensive care patients’ vital

functions during recovery from cardiac or pulmonary

trauma (What Is Cardiopulmonary Bypass?, 2004).

Patients are connected to ECMO via cannula and

tubes and their deoxygenated blood is drained and

pushed through an oxygenation membrane using a

pump (“What Is ECMO?,” 2016). The membrane

facilitates blood oxygenation, and the pump draws

and returns the blood to the patient; replacing the

patient’s lung and/or heart function (“What Is

ECMO?,” 2016).

Recent technological advancements in ECMO

have made it a simpler and safer procedure; boosting

survival rates up to 70%, across age groups and

making ECMO an increasingly adopted technique

(MacLaren et al., 2012; Nichani, 2011).

Consequently, the demand for highly trained

individuals that can operate the machine has

increased. ECMO, although lifesaving, is vulnerable

to a plethora of mechanical complications which can

cause mortality. Common ECMO complications on

the machine side are air entrainment, oxygenator

failure, pump failure, and blood clots (Lafçı et al.,

2014). Such high risk emergencies require ECMO

staff to process critical problem identification skills,

make quick interventions, have common behavioral

patterns to work as an effective team, and good

communication skills to decrease ECMO support

suspension; hence avoiding mortality (Peets & Ayas,

2013).

ECMO educators have used simulation modalities

to create realistic and high risk scenarios to instill

positive technical and behavioral patterns in their

trainees (Brazzi et al., 2012; Chan et al., 2013).

However, due to lack of support, ECMO simulation

methods are still relatively primitive. They consist of

modifying a mannequin to enable circulation,

connecting the mannequin to a colored water filled

ECMO circuit, and using workarounds like manually

injecting air into the circuit to trigger alarms and

initiate the simulated emergency (Anderson et al.,

2006; Ng et al., 2016). Current ECMO simulation

practices suffer from high initial and reoccurring

costs due to the use of medical equipment and

Noorizadeh, M., Alsalemi, A., Alhomsi, Y., Bensaali, F. and Meskin, N.

A Thermochromic Ink Heater-cooler Color Change System for Medical Blood Simulation.

DOI: 10.5220/0010264001070113

In Proceedings of the 14th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2021) - Volume 1: BIODEVICES, pages 107-113

ISBN: 978-989-758-490-9

107

expensive circuit consumables such as the

oxygenation membrane. It also offers little fidelity

and interactivity relative to the cost; the circuit does

not visually simulate blood oxygenation color

differentials unless they use real blood and

deoxygenate the it with carbon dioxide (CO

)

through a modified circuit, but the display of custom

information on the ECMO console often remains a

challenge.

Thermochromic ink is a special ink with a

chemical composition that reacts to temperature by

changing its hue (Abdullah Alsalemi, Aldisi, et al.,

2017). The ink can be customized to switch between

two colors at a set temperature; for example, going

from red to invisible when a pizza box is under 40°C.

On the other hand, the blood oxygenation process is

where the lung (or ECMO oxygenator) exchanges

blood CO

for oxygen (O

). The oxygenation process

is visually represented with a clear blood color

differential; blood changes from dark red to red as it

loses CO

and gains O

. Blood color differentials

serve as an important diagnostic tool for ECMO staff;

indicating lack of oxygen in the circuit.

Thermochromic can be used to simulate blood

oxygenation by customizing it to shift between dark

red and red and placing it within a system that

continuously manipulates its temperature above and

below a defined threshold. Incorporating

thermochromic ink into current ECMO simulation

practice means increased fidelity; by introducing the

oxygenation visual effect, and reduced cost; by

getting rid of expensive consumables that do not

introduce any actual functionalities to the simulation

environment.

In order to operate thermochromic ink in ECMO

simulations, a temperature control system is needed.

It also needs to be compact, efficient, and

controllable. In this paper, we are presenting a novel

heater-cooler system for thermochromic ink control,

where oxygenation and deoxygenation can be

simulated.

The remainder of this paper is organized is

follows. Section 2 describes the overall simulation

system. Section 3 elaborates on the design of the

heater-cooler system. Section 4 presents and

discusses preliminary results of the first prototype.

The paper is concluded with future work in Section 5.

2 OVERVIEW OF THE

MODULAR ECMO

SIMULATOR

This section describes the research and development

processes behind the proposed ECMO training system.

The training system is focused on practically training

practitioners for ECMO on adult patients (A. Alsalemi,

Al Disi, et al., 2017). The system is expected to be used

alongside a strong theoretical course to develop a solid

foundation. Figure 1 depicts the proposed system’s

block diagram comprising three physical subsystems:

the patient unit, the ECMO unit, and the oxygenator all

centered around the thermochromic loop. Each unit

includes simulation modules as shown in the diagram.

To control the operation of those modules, a

communications system is developed, and connected

to a tablet application for instructors to steer the

training experience for a smooth learning experience.

Figure 1: Overview of proposed training system.

The thermochromic loop is a system designed

around using thermochromic ink to simulate basic

ECMO functionalities; circulation and oxygenation.

The patient unit contains a tank that houses a

thermochromic ink mixture diluted in water and

includes red and black. The black ink can be

deactivated and activated above and below 30°C

respectively. The thermochromic mixture is pushed

through the circuit using a brushless DC pump. It

goes out of the patient unit and heads towards a mock

oxygenator which bypasses it to the heater unit below.

The heater unit heats the mixture causing it to lose its

dark color; simulating oxygenation. The mixture then

returns to the patient station where it is cooled down;

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Figure 2: Block diagram of the thermochromic heater-cooler system.

gaining its dark color back and simulating

deoxygenation.

The loop function relies on continuously adding

and removing heat in and out of the mixture; making

the appropriate design of the heat exchange process

of utmost importance.

The proposed system is constituted of the primary

and secondary loop. The primary loop is where the

thermochromic mixture flows; it includes two heat

exchangers (one with a cold-water stream and another

with a hot-water stream), a pump, and a reservoir tank

placed inside the patient unit. The secondary loop is

between the source of the water streams and the heat

exchangers (Al Disi et al., 2018).

In addition, the simulator contains a variety of

simulation modules, each specially designed to

physically, audibly, or haptically imitate a certain

ECMO phenomena. Examples include line breakage,

patient bleeding, head pump noise, among others (Al

Disi et al., 2017).

Moreover, the simulator system has been

holistically thought out in the point of views of both

the learner and the instructor (Alhomsi et al., 2018;

Abdullah Alsalemi et al., 2018; Abdullah Alsalemi,

Homsi, et al., 2017). The teaching aspect has been

supported by the development of two innovative

software components: the instructor tablet application.

The application is comprised of two parts: the scenario

designer and the live control panel, both connected to

a CouchDB cloud server for parameter and wireless

scenario transmission (Al Disi et al., 2019).

3 METHODS

3.1 Thermoelectric Module

The fundamental underlying operation of the

thermochromic loop is heat exchange;

increasing/decreasing temperature to above/below

the ink’s specific deactivation temperature. The ink

mixture used is a combination of black and red, with

deactivation temperatures of 31°C and 47°C

respectively. In this case, the ink used has a

transitional region between 27℃ to 32℃; where the

liquid color moves between light and dark red. Thus,

the heat exchange process is required to cool/heat the

liquid below/above the transitional region.

A thermoelectric module is a transducer that can

generate electricity by applying heat and vice versa

(i.e. the Peltier effect). Indeed, by injecting current to

the thermoelectric module, heat can be produced.

Therefore, when the current is fed to thermoelectric

module, it flows through two different semi-

conductors, and consequently, the heat or the cold

will be generated. In the other words, a thermoelectric

module has two faces, once one of them gets cold, the

other face become hot. Furthermore, the performance

of cooling side is directly related to the heating face,

which means that, by decreasing the temperature of

the heating side, the performance of cooling side will

increase significantly.

3.2 System Design

In order to demonstrate the visual effect of blood

color change, the color of thermochromic ink in the

simulator needs to simulate the different states of

human blood. Thus, the heater-cooler prototype has

been designed and developed in order to satisfy the

simulator’s needs.

Therefore, the prototype is split into three main

subcomponents: A) main tank for supplying blood, B)

the cooling unit, and C) the heating unit.

3.2.1 Main Tank

In this stage, blood is transmitted into the next stage

(the cooling unit) by a controllable pump, and

eventually, passed to the last stage (the heating unit)

when returning back to the same tank.

A Thermochromic Ink Heater-cooler Color Change System for Medical Blood Simulation

109

3.2.2 Cooling Unit

As illustrated in Figure 2, the cooling unit consists of

the following components.

• Thermal exchanger

• Ceramic thermoelectric

• CPU cooling module

• Tank (Koolance BDY-TK120X70) and

pipes

• Water or coolant

• Aluminum water/coolant cooling block

• Pump (Koolance PMP-300)

• Flow Meter (Koolance INS-FM14)

• Temperature sensor

As shown in Figure 2, the thermal exchanger has

4 ports: IN1, IN2, OU1, and OUT2. Accordingly, the

blood is delivered to IN1, and goes out from OUT1.

Meanwhile, the cooling unit affects the blood

entering to IN2, and then goes out from OUT2.

Indeed, by placing two thermoelectric modules on the

aluminum water/coolant cooling block, the

temperature of the water/coolant inside this block will

decrease. It will also circulate, by a controllable

pump, between the cooling tank and the thermal

exchanger unit. In the other hand, two CPU cooling

modules decrease the temperature of the heating side

of the thermoelectric module. The unit components

have been selected from the same manufacturer to

ensure compatibility and fitting.

Moreover, due to the considerable effect of

flowrate on the cooling performance, several flowrate

meters have been implemented in the circuit after

each pump. In the other words, by increasing the

flowrate, the cooling effect dramatically decreases for

the cooling unit. However, flowrate is a significant

key factor in this prototype, and it is not negligible.

Therefore, by finding the trade-off between the

flowrate and appropriate temperature, the overall

performance can be optimized.

3.2.3 Heating Unit

As illustrated in Figure 2, a heating unit consists of

the following components:

• Tank (Koolance BDY-TK120X70) and pipes

• Pump (Koolance PMP-500)

• Heater module

• Flow meter (Koolance INS-FM14)

• Thermal exchanger (Koolance HXP-193)

• Water

The heating unit includes almost the same cyclic

process as the cooling unit. However, in order to heat

up the tank’s water, a heating element is used. Indeed,

in order to optimize the performance in the compact

size, the 3D printer’s hot-end heater has been

employed in this prototype. Hence, by placing the

heater inside the water tank, water’s temperature will

increase. Likewise, the unit components have been

selected from the same manufacturer to ensure

compatibility.

The tanks are: the thermochromic ink’s tank, cold

water’s tank, and hot water’s tank. Furthermore, three

pumps correspond to each tank. Indeed, the

thermochromic ink’s tank contains the bright ink all

the time. Therefore, by injecting ink to the cooling

unit, the ink’s color will turn to dark red.

At this point, the ink will transfer to the heater unit

to turn the color back to light red. The entire liquid

flow is circulating via those three pumps explained

earlier. Due to the proportional effect of flow and the

performance of the heater/cooler, three flowrate

meters have been implemented in the circuit in order

to control flowrate, and eventually, improve the entire

process to operate autonomously.

In addition, power supply is also provided in order

to supply power to pumps, CPU cooling systems,

heater, flowrate meters, and the thermoelectric

modules. Moreover, the flowrate of motors can be

controlled by voltage adjustment.

4 RESULTS AND DISCUSSION

In this section, light is shed on preliminary results of

the prototype thermochromic heater-cooler system.

The prototype was developed at Qatar University. It

is worth noting that, in this initial version,

thermoelectric modules were used in both the cooling

and heating units. Also, the system has been initially

tested with successful color transformation of blood

color from dark bright (cold) to bright red (hot). This

is shown in Figure 3. More specifically, bright red

simulated blood refers to oxygenation, which is the

normal and healthy state for human organ function.

On the other hand, simulating dark red refers to

deoxygenation, which is a hypoxemic, unhealthy

state. To achieve the oxygenation state, the fluid

temperature has to exceed 35°C, conversely,

hypoxemia can be simulated when cooling the fluid

to under 25°C.

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Figure 3: Color change effect achieved by heater-cooler

system prototype.

With several tests undertaken on the cooling unit,

the following results are attained. By increasing the

flow rate to approximately 5 L/min, and raising the

temperature to 35°C degrees, it is evident that color

of the thermochromic ink turns to bright red. On the

flip side, by dropping the flow rate to approximately

3 L/min or less, the temperature can drop readily to

below the temperature to 25°C degrees, showing dark

red simulated blood. We have observed an inverse

relation between flow rate and cooling efficiency, i.e.,

the lower the flow rate, the faster the fluid cools

down, achieving simulated hypoxemia.

Figure 4 shows the current prototype of the

thermochromic heater-cooler system. For simplified

analysis the system has been minimized to a single,

closed loop. It is also worth noting that the tests

conducted proved that the two color states are

reversible, with average transition time of 25 sec.

The system includes a number of limitations.

First, a single, closed loop was deployed, however,

higher heating and cooling efficiencies can be

achieved by separating the units, enabling

independent heating and cooling functionalities.

Second, proper more effective heating modules

should be used to significantly increase the heating

efficiency. Third, an automated control system is to

be developed to enabled dynamic adjustment of flow

rate to achieve the desired effect without human

intervention.

From a cost-effectiveness standpoint, the current

prototype can be developed with an equipment cost

of less than 500 USD. Compared to using an actual

ECMO machine with real blood (i.e. more than

100,000 USD depending on the machine brand), the

proposed solution is a powerful alternative for

simulations.

In the next prototype of the system, the heater-

cooler will be integrated with the simulator’s patient

unit, allowing it to be controlled by the instructor

tablet application. Also, the aforementioned

limitations are to be addressed as well as packaging

the system as a compact module for increase

portability.

Figure 4: Current prototype of thermochromic heater-cooler system.

A Thermochromic Ink Heater-cooler Color Change System for Medical Blood Simulation

111

5 CONCLUSIONS

In this paper, a novel thermochromic heater-cooler

system is presented as part of the modular ECMO

simulator. Developed upon thermochromic ink, cost-

effective blood simulation is achieved by temperature

adjustment, simulating oxygenation and hypoxemia.

The system has been developed as a prototype with

successful and reversible transitions between dark

and bright red blood color. After addressing the

limitations, the heater-cooler will be integrated with

the ECMO simulator, allowing unpreceded cost-

efficient simulation possibilities.

ACKNOWLEDGEMENTS

This paper was supported by Qatar University Internal

Grant No. M-CTP-CENG-2020-1. The findings

achieved herein are solely the responsibility of the

authors.

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