Non-enzymatic Glucose Sensor with CuO Nanowires on a Transparent, Flexible SubstrateCaroline 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 cellulose d)ester (MCE) membrane filter. Filter with CuO NWs compressed face down on e)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/PBS h)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, thenumber of diabetics should increase to 300 million people in nearly 10 years. Diabeticsneed efficient and cost effective biosensors to assess their glucose levels and determinewhich 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 monitorthe individual’s sugar levels. Many continuous glucose monitors exist; however, they allrequire the puncture of the skin to gain access to tissue fluid.Without the focus on enzymes, instability and costs no longer reduce the accuracy andpracticality of the biosensor. Thus, much research is geared towards creating aninexpensive, stable, sensitive and accurate non-enzymatic glucose sensor.4 Withoutenzymes, these sensors cannot distinguish glucose from other biological components—such as uric acid, ascorbic acid, sucrose, and fructose. Therefore, the sensing materialmust work well in solutions containing typical and high concentrations of theseinterfering 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.

10 1. 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 NWsensor placed on Louisiana Tech logo todemonstrate transparency, (b) picture ofbent CuO NWs sensor as indication offlexibility, (c) 3D model of CuO NW sensorduring experiment