1. Non-enzymatic Glucose Sensor with CuO Nanowires on a
Transparent, Flexible Substrate
Caroline Bell1,2, Amit Rai2,3, & Dr. Arden Moore2,4
1Biomedical Engineering, 2Institute for Micromanufacturing, 3Micro- and Nanoscale Systems
Engineering, and 4Mechanical Engineering - Louisiana Tech University, Ruston, LA, 71272
Figure 1: Illustration of sensor fabrication.
Cu & graphite in CuSOa) 4: 30 min. of electroplating at
0.02A.
Cu oxidized in Vulcanb) TM 3-550 oven at 450 ̊C for 6 hr.
CuO in DI Hc) 2O sonicated for ~5 s.
Solution vacuum filtered through mixed cellulosed)
ester (MCE) membrane filter.
Filter with CuO NWs compressed face down one)
1”x1” polyethylene terephthalate (PET) plastic film
with a hydraulic press at 5,000 psi for ~20 min.
Filter removed.f)
Dilute Nafion layer added to protect NW network.g)
PDMS reservoir attached to hold glucose/PBSh)
solution.
Preparation CuO NWs Sensor
Figure 3: Average current measured across CuO NWs sensor under the presence of 0-12 mM
glucose and a constant applied voltage of (a) 0.3 V, (b) 0.45 V, (c) 0.6 V, and (d) 0.6 V after the
sensor was bent 5 times
a)
b)
c)
d)
Electrochemical Measurements
Characterization of the NWs
Figure 4: (Top Row) SEM images of pre-sonicated CuO (a) micro-particles
with nano-sized extensions, (b) close up of extensions, and (c) close up of
one individual NW (Bottom Row) SEM images of post-sonication CuO (a)
near central area of deposition on PET, (b) near edge of sensor’s PDMS
reservoir, and (c) NW at outer edge of sensor’s PDMS reservoir
c)b)a)
Figure 5: (a) Raman spectrum and (b) EDX spectrum of CuO NWs. The standard
range for peaks in the CuO Raman spectrum occur around 282-298 cm-1, 330-346
cm-1, 465 cm-1 and 616-632 cm-1. 3, 4 Si peak in EDX attributed to the supporting Si
chip used for imaging.
1 Who.int,. (2016). WHO | Diabetes: the cost of diabetes. Retrieved 18
February 2016, from
http://www.who.int/mediacentre/factsheets/fs236/en/
2 Zhang, Y., Liu, Y., Su, L., Zhang, Z., Huo, D., Hou, C., & Lei, Y. (2014).
CuO nanowires based sensitive and selective non-enzymatic
glucose detection. Sensors And Actuators B: Chemical, 191, 86-93.
http://dx.doi.org/10.1016/j.snb.2013.08.096
3 Rashad, M., Rüsing, M., Berth, G., Lischka, K., & Pawlis, A. (2013).
CuO and Co3O4 nanoparticles: synthesis, characterizations, and
raman spectroscopy. Journal of Nanomaterials, 2013, 1-6.
4 Wei, T. (1991). Raman scattering of cupric oxide (1st ed., p. 60).
British Columbia: Simon Fraser University. Retrieved from
http://summit.sfu.ca/system/files/iritems1/7880/b1442972X.pdf
5 Abikshyeet, P., Ramesh, V., & Oza, N. (2012). Glucose estimation in
the salivary secretion of diabetes mellitus patients. Diabetes,
Metabolic Syndrome and Obesity: Targets and Therapy, 5, 149–
154. http://doi.org/10.2147/DMSO.S32112
6 Gupta, S., Sandhu, S. V., Bansal, H., & Sharma, D. (2015).
Comparison of Salivary and Serum Glucose Levels in Diabetic
Patients. Journal of Diabetes Science and Technology, 9(1), 91–96.
http://doi.org/10.1177/1932296814552673
CuO NWs with an average diameter of 35.5 nm were obtained.
SEM images and EDX and Raman spectra confirmed the presence
of CuO NWs. The CuO NW-based sensor detected the following
ranges of current at applied voltages of 0.3 V, 0.45 V, and 0.6 V
(before and after bending the sensor) respectively: 2.43-41.7 pA,
12.22 pA-1.38 nA, 16.98 pA-10.81 nA and 20.43 pA-14.26 nA.
The current range increased with each increase in applied
voltage. Accordingly, the CuO NWs’ resistivity decreased with
increasing voltage, which is typical of a semiconducting material.
The biosensor detected increases in Gl content well-above the
typical amount measured in human tears, 0.14 mM.2
Additionally, the sensor detected concentration changes included
the range of two groups of Type-2 diabetics’ saliva Gl (0.02-
1.01mM),5 and (0.78-1.39 mM).6
These results show our transparent, flexible device effectively
uses CuO NWs to act as a non-enzymatic Gl sensor.
Diabetes is a rampant health problem across the world. According to WHO, the
number of diabetics should increase to 300 million people in nearly 10 years. Diabetics
need efficient and cost effective biosensors to assess their glucose levels and determine
which and how much drugs they need to prevent greater health risks, such as death.3
The efficiency of a glucose sensor relies heavily on its ability to continuously monitor
the individual’s sugar levels. Many continuous glucose monitors exist; however, they all
require the puncture of the skin to gain access to tissue fluid.
Without the focus on enzymes, instability and costs no longer reduce the accuracy and
practicality of the biosensor. Thus, much research is geared towards creating an
inexpensive, stable, sensitive and accurate non-enzymatic glucose sensor.4 Without
enzymes, these sensors cannot distinguish glucose from other biological components—
such as uric acid, ascorbic acid, sucrose, and fructose. Therefore, the sensing material
must work well in solutions containing typical and high concentrations of these
interfering compounds.
In one study, Zhang et al. (2014) found that CuO nanowires (NWs) selectively and
accurately sensed glucose, even in the presence of these electroactive compounds .4
This group used the nanowires in a non-flexible, non-enzymatic glucose sensor. The
effectiveness of the CuO NWs led us to presume CuO would provide the desired
sensitivity and performance in a novel flexible glucose sensor. Our research team
devised a method for creating CuO microparticles with evenly distributed extensions.
These extensions were the source of CuO NWs used in this experiment.
Preparation of Solutions and Experimental Setup
I would like to thank my advisor, Dr. Arden Moore, for dedicating so
much time and supporting me throughout this project. His patience and
terms of endearment were crucial to my efforts and the results of this
research. Our Moore research team members also aided in the
accomplishments of this project, especially team member Amit Rai. I
also owe a lot of thanks to LA Tech’s Institute for Micromanufacturing
for providing high-quality equipment and the courteous staff.
Finally, I would also like to thank LA EPSCoR for granting funds to my
advisor and I so that we could begin this project. This work was
supported through a grant from the Louisiana Board of Regents through
the Supervised Undergraduate Research Experiences (SURE) program,
contract number LEQSF-EPS(2014)-SURE-113.
101. mM PBS solution & four stock solutions—2 mM Gl in DI H2O, 4 mM Gl in DI H2O, 10
mM Gl in DI H2O, and 30 mM Gl in DI H2O— were prepared for testing the performance
of the sensor.
Gold2. -plated working electrode contacted outer area of NWs outside PDMS ring;
platinum wire reference electrode contacted NWs and solution within PDMS ring.
3. 2μL PBS submerged into the PDMS reservoir as 0 mM solution; next, pre-calculated
volumes of four stock solutions were added sequentially to the PBS to obtain exact
concentrations of Gl from 1 to 12 mM.
Methods
Introduction Results Conclusion
Acknowledgements
References
Figure 2: (a) Picture of actual CuO NW
sensor placed on Louisiana Tech logo to
demonstrate transparency, (b) picture of
bent CuO NWs sensor as indication of
flexibility, (c) 3D model of CuO NW sensor
during experiment