Third Day Poster Session, 17 June 2010 - NanoTR-VI

P
P
P,P
P andP
Poster Session, Thursday, June 17
Theme F686 - N1123
Development of a Humidity Sensor Using PEGR40R-Stearate
1
1
1
2
1
Umut Alper TekinP P, Ramazan slamoluP P, Sevgi Klç ÖzdemirP
PSalih OkurP
PUEkrem ÖzdemirUP P*
1
PDepartment of Chemical Engineering, Izmir Institute of Technology, Izmir, 35430 Turkey
2
PDepartment of Physics, Izmir Institute of Technology, Izmir, 35430 Turkey
Abstract-A humidity sensor was developed using Polyoxyethylene Stearate (PEGR40R-St), which was drop-casted over a quartz crystal
microbalance (QCM). The response time to different humidity levels were tested and found that the humidity sensor using PEGR40R-St was
responded to the humidity changes much faster than that for a commercial humidity sensor.
Relative humidity plays an important role in human life. For
the comfort and health of humans, continuation of biological
processes, preservation of goods, and proper operation of
machines and devices, relative humidity needs to be
maintained at desired humidity level. Although a large number
of research has been conducted using different sensing
materials with various sensing mechanisms, new materials and
methods are being sought for improving the current humidity
sensors.[1-6] Use of a quartz crystal microbalance (QCM) has
received a lot attention to detect the various kinds of gaseaous
and vapors of organics. The quartz crystal microbalance
consists of a quartz crystal sandwiched between two metal
gold electrodes. Applying an alternating electric potential
across the crystal induces vibrational motion of the crystal.
These vibration motions results in a transverse acoustic shear
wave which propagates through the crystal. When a mass is
deposited on the top of the crystal, resonace frequency
changes, which in turn, the change in the resonant frequency
can be related to the mass coated on the electrode surface.
Therefore, the use of this technique with a humidity sensing
element is expected promising to detect the humidity at
various levels Being highly hydrophilic, polyethylene glycol
stands as a very good candidate for humidity sensing
applications. In the present study, QCM surface was coated
with PEGR40R-St with a drop-casting method. Hydrogen atoms
of the water molecules are expected to make strong bonds
with the ether oxygen atoms in the PEG chains, resulting of
accumulation of water on the quartz crystal.
Figure 1 shows the comparison of the PEG40-St and a
commercial humidity sensor to the relative humidity change.
As can be seen in the figure, the developed sensor responded
the relative humidity change much faster than the commercial
humidity sensor.
Figure 2 shows the repeatability of the PEGR40R-St to the
humidity change. The relative humidity values seen in the
figure were obtained from the commercial humidity sensor. As
can be seen from the figure, the PEGR40R-St shows a promising
result on the determination of the relative humidity. The
hysteresis seen in the figure was related to the data obtained
from the unattained equilibrium in the commercial humidity
sensor due to its higher response times. The fact that the
response time for the commercial sensor were found to be
much higher. Therefore, we suggest that the PEGR40R-St could
be developed as a humidity sensor with a much shorter
response time.
F, Hz
50
0
-50
-100
-150
-200
-250
dF/Hz Relative Humidity (%)
152 160 168 176 184 192 200
Time/min
Figure 1. Comparison of PEGR40R-St and a commercial humidity
sensor to the relative humidity change.
f (Hz)
100
0
-100
-200
-300
-400
-500
PEG Nanofilm
20 30 40 50 60 70 80 90
Relative Humidity (%)
Figure 2. Repeatability of the PEG40-St humidity Sensor to the
relative humidity change.
1.run
2.run
3.run
*Corresponding author: HTekremozdemir@iyte.edu.trT
[1] Y. Zhang, K. Yu, R. Xu, D. Jiang, L. Luo, Z. Zhu, Quartz crystal
microbalance coated with carbon nanotube films used as humidity
sensor, Sens. Actuators A 120 (2005) 142–146.
[2] F.P. Delannoy, B. Sorli, A. Boyer, Quartz crystal microbalance
(QCM) used as humidity sensor, Sens. Actuators B 84 (2000)
285–291.
[3] P.R. Story, D.W. Galipeau, R.D. Mileham, A study of low-cost
sensors for measuring lowrelative humidity, Sens. ActuatorsB24–25
(1995) 681–685.
[4] P.G. Su, Y.L. Sun, C.C. Lin, Novel low humidity sensor made
ofTiO2 nanowires/poly(2-acrylamido-2-methylpropane sulfonate)
composite material film combined with quartz crystal microbalance,
Talanta 69 (2006) 946–951.I
[5] P.G. Su, Y.L. Sun, C.C. Lin, A low humidity sensor made of
quartz crystal microbalance coated with multi-walled carbon
nanotubes/Nafion composite material films, Sens. Actuators B 115
(2006) 338–343.
[6] H.W. Chen, R.J. Wu, K.H. Chan, Y.L. Sun, P.G. Su, The
application of CNT/Nafion composite material to low humidity
sensing measurement, Sens. Actuators B 104 (2005) 80–84.
90
80
70
60
50
40
30
20
Relative Humidity (%)
6th Nanoscience and Nanotechnology Conference, zmir, 2010 703