Transportable Infant Incubator
for Developing Countries
R. Cichocki, A. Midouin, and R. O’Laughlin; Advisor: B.F. BuSha
Department of Biomedical Engineering, The College of New Jersey, Ewing, NJ
Structural Design
Abstract
Power consumption by the electronics will be
negligible compared to the expected 200W
max from the heating element. The power
consumption of the electronics is 340 mW to
610 mW. Prototype testing was performed
using an acrylic case, fans, vents, a 12 V 35
Ahr battery, and four headlights. The results
are seen below. The estimated time for the
battery to reach 11V while operating is 100
minutes. The incubator target temperature was
reached at 7 minutes.
• The frame of the incubator is composed of
two sections, which includes the casing
surrounding the heating mechanism and its
controls and the upper portion that will contain
the infant.
• The lower frame is comprised of aluminum
3003 plates. The upper frame is a transparent
polycarbonate casing.
• The incubator is assembled with corner
blocks, base blocks, and machine screws.
12.8
Fig. 2: Structural design of incubator (in progress).
Design of Temperature
Pulse Width Modulation
Controller
Control System
11.8
11.6
11.4
11.2
11
555D
C4
.22u
5VSource
C3
.01u
8
VCC
8
5
OS2
V+
2
4
5
6
7
2k
C2
.1u
TRIGGER
RESET OUTPUT
CONTROL
THRESHOLD
DISCHARGE
R19
3
0
0
2.5V_VirtGround
Battery
0
12VBattery
R11
AC =
TRAN =
DC = 12
Dif f Amp
6
5
OS1
LM741
OUT
OS2
+
U3
R9
2
R5
2
5VSource
5k
U2
LM7805C
OUT
C5
.1u
1k
R10
3
IN
3
1
V-
4
0
GND
5VSource
5k
R6
5k
1
12VBattery
C6
.32u
0
5VSource
1k
0
R8
2k
R12
5VSource 5k
4
R7
2k
1
6
2.5V_VirtGround
5
V-
OS1
LM741
OUT
OS2
7
+
V+U5
2
R29
2k
3
R30
2k
5VSource
2.5V_VirtGround
Power
Supply
0
Sensor &
Amplifier
D3
D5
D1N4001
D1N4001
5VSource
Dif f Amp
R18
10K
SET = 0.55
U4A3
V+
9
+
OUT
4
R13
1k
- 12
LM339
OUT
8
R25
2k
- 12
LM339
R27
1k
D2
5
U1A3
4
- 12
U7D3
V+
R1
1k
11
5VSource
U6D3
V+
+
2
OUT
10
V-
- 12
LM339
LM339
13
V-
0
13
R28
D6
5VSource
2k
- 12
D1N4001
V-
0
Temperature &
Battery Warning
R26
2k
0
12VBattery
D4
D9
D1N4001
D1N4001
5VSource
R21
20K
SET = 0.775
R24
10k 5
U6A3
V+
R2
1k
7
+
OUT
- 12
LM339
D7
D1N4729
0
5VSource
U6B3
V+
+
2
OUT
4
1
6
- 12
LM339
V-
30.0
25.0
20.0
15.0
10.0
5.0
2
4
6
8
10
12
14
V+
+
OUT
10
+
OUT
Dif f Amp
D1N4001
35.0
Time (min)
5VSource
0
D8
D1N4001
40.0
0
V-
5VSource
R17
10K
SET = 0.45
45.0
14
11
0
14
0.0
5VSource
U6C3
V+
+
2
V-
12
5VSource
5VSource
5
10
50.0
555D
Control
8
Prototype Temperatures
M1
IRLZ34N
1k
Temperature (Celsius)
+ 7
U8
Control
R4
3
6
Time (min)
X1
GND
3
6
R15
2k
TRIGGER
RESET OUTPUT
CONTROL
THRESHOLD
DISCHARGE
4
1
62k
1
GND
Dif f Amp
VOS1
LM741
OUT
2
RLoad
10
R3
25k
X2
VCC
2
4
5
6
7
4
2
LM339
• The controller will regulate heating
element power by pulse width
modulation (PWM) created using
two 555 timing chips. This will
reduce power loss by the transistor.
12
0
R14
62k
2.5V_VirtGround
• The output of the measurement
circuit will be an input to the
controller, which will be physically
realized with one operational
amplifier, as described in [6].
Currently only shown as an
integrator.
12.2
47u
7
• A buzzer and LED will warn when
the temperature is out of range or
the battery charge is low.
12.4
5VSource
R31
• The measurement circuit will
monitor air/skin temperature and
the voltage of the 12 V battery. This
circuit will be used to verify if the
temperature is within 33.5  2oC, a
range derived from E. N. Hey [5].
12.6
12VBattery
C1
V+
An incubator is a medical device which can maintain
and regulate an appropriate environment for infants.
This is a crucial device for preterm infants, which are
infants born before 37 weeks of gestation [1]. Their low
birth weight and under developed organs make them
very sensitive to environmental humidity, temperature,
and infection. Preterm birth rates range from 5% in
developed countries to 25% in developing countries
[2]. Furthermore, most births in developing countries
do not occur in a hospital. The World Health
Organization and Engineering World Health stress
these facts and the need for a transportable infant
incubator designed for use in developing countries.
The incubator needs to be robust to withstand travel
through difficult conditions and cost effective since it
will be used in low resource areas [3]. Parts need to be
inexpensive and easily replaced in developing
countries. Previous incubators were researched and
the proposed project draws from the work of the Car
Parts Incubator and Engineering World Health [1,4].
Battery Voltage (V)
• The ventilation system, located within the
lower frame, consists of aluminum vents,
halogen headlight bulbs, computer fans, and
a humidifier.
0
Introduction
Battery Voltage
13
1
Premature infants make up 25% of all births in
developing countries and are usually born outside of a
hospital. The World Health Organization and
Engineering World Health have stressed the need for a
transportable infant incubator designed for use in
developing countries. The goal of this project is to
create a device which protects and incubates an infant
while being transported to a hospital. The device needs
to be economical, robust, and use easily replaceable
parts. The heating mechanism will use computer fans,
a humidifier, and car headlights to provide heat. The
temperature will be automatically maintained by a
proportional integrative derivative (PID) controller.
Large temperature deviations and low battery charge
will be announced through an audible alert. The base
will be made of aluminum due to its low cost and
durability. The bassinet cover will be polycarbonate due
to its low thermal conductivity and strength. A
theoretical MATLAB model of the preterm infant and
incubator will be implemented to evaluate the
performance of the design. Testing goals will include
finding average power consumption, times to reach
target temperature (33.5oC), and the safety of the
device.
Results
V-
0
0
Fig. 3: Schematic of current electrical design.
Testing
• Testing and verification will employ a MATLAB model of an incubator to simulate its function and provide data for
comparing measured values. To construct a theoretical model, the compartmental model previously developed by Simon
and Reddy [7] and Yassel [8] will be used.
• A verification device that models the volume, surface area, and approximate shape of an infant will be utilized to predict
the heat conduction within the incubator. This device will be made of low-density polyethylene to approximate the thermal
conductivity of an infant’s skin and contain fluids heated by a submersible heater to mimic metabolic heat [9].
Fig. 5: (Top) change in battery voltage over
time. (Bottom) measured temperature at the
middle of the incubator and at the inlet. The
red squares are the inlet temperature and
the blue diamonds are the temperature in the
center of the prototype.
Conclusions
Prototype testing shows that the design can
heat the system beyond requirements in a room
temperature environment. Future work will
include
finishing
structural/ventilation
construction, integrating the electronics with the
structure, testing in different temperature
environments, and tuning the system to
specifications. The presented design can be
adjusted to satisfy local manufacturing
capabilities. The design can be further
developed by including a breathing monitor,
oxygen control, and humidity sensor.
References
Fig. 1: Functionality and cost relationship
of proposed design and other designs.
Fig. 4: MATLAB model of incubator and control system. Will be used for testing and verification.
[1] Engineering World Health. (2010, December). Engineering World Health: Projects that Matter
[Online]. Available: http://ewh.org/index.php/programs/technology/design/
[2] P. Steer , “The epidemiology of preterm labour,” BJOG-Int. J. Obstet. Gy., vol. 112, issue. s1,
pp. 1–3. Feb. 2005, doi: 10.1111/j.1471-0528.2005.00575.x [3] World Health Organization. Medical
Devices: Managing the Mismatch. [Online]. Available: http://www.who.int/medical_devices/access/en/
[4] Design that Matters. (2011, November 29) NeoNuture: the "Car Parts"
Incuabator.[Online].Available: http://designthatmatters.org/portfolio/projects/incubator/
[5] E. N. Hey, and G. Katz, “The optimum thermal environment for naked babies.” Arch. Dis. Child.,
1970, vol. 45, no. 241, pp. 328-334, June 1970. doi:10.1136/adc.45.241.328
[6] V. Michal, C. Prémont, G., Pillonet, and N. Abouchi, "Single active element PID controllers,"
Radioelektronika (RADIOELEKTRONIKA), 2010 20th International Conference , vol., no., pp.1-4, 1921 April 2010
[7] B. Simon, and N. Reddy. "A theoretical model of infant dynamics." J Biomech Eng-T ASME, vol.
116, pp. 263-269, August 1994
[8] A.T. Yassel. “A simulation model of infant - incubator - feedback system with humidification and
temperature control,” unpublished.
[9] K. Holmes. "Thermal conductivity data for specific tissues and organs for humans and other
mammalian species." Thermal Properties. 1990