Microfluidic device based on graphene [630384]

Microfluidic device based on graphene

Bianca Tincu *, **, Marioara Avram *, Cristina Pachiu *, Eugen Chiriac *, Corneliu Voitinc u*,
Andreea Cristina Costache *, ***, Maria – Roxana Marinescu *, ***, *

* National Institute for Research and Development in Microtechnologies – IMT Bucharest, 126A,
Erou Iancu Nicolae Street, 077190, Voluntari -Bucharest, ROMANIA,
** University Politehnica of Bucharest, Faculty of Applied Chemistry and Materials Science, 7, Ghe orghe Polizu Street,
Bucharest, ROMANIA
*** PhD. Student, M.Sc. Ing., at Politechnica University of Bucharest, Faculty of Industrial Engineering and Robotics , 313
Splaiul Independentei, sector 6, Bucharest, ROMANIA,

*E-mail : [anonimizat] , [anonimizat] , [anonimizat] , eugen.chiria [anonimizat] ,
[anonimizat] , [anonimizat] , *[anonimizat]

Abstract— In the last years, there has been a big
progress regarding the development of graphene -based
microfluidics. Based on the excellent biocompatible
properties of graphene and derivatives, a large variety of
microfluidic dev ices with graphene integrated are used in
the medical field. They are used for detection of viruses that
lead to different diseases, drug delivery or for cell analyses ,
detection of protein and glucose, detection of contaminants,
application of sensors or material preparation, gene
structure and function, DNA research, cellular research,
protein and amino acid research. The purpose of this paper
is to show the importance of graphene as a material in
fabricating sensors used at microfluidic devices and also to
illustrate the costs involved in the production process.
Keywords — graphene, microfluidics, spectroscopy.

1. Introduction

Microfluidics contributes to the science
and study of the systems in which the scale of
involving fluid manipulation varies from a
few microns up to a few millimeters [1].
Microfluidics can be employed in numerous
biological studies becau se of its precision,
sample efficiency, portability, and low‐cost
production. For the past two decades, the
demand for con tinuous and fast -response
measurements using small volumes and low
concentration samples has been the driving
force for research . Microfluidics has been
advancing rapidly and has progressed from
basic devices, such as : a channel, a valve or a
pump, to larg e-scale two -dimensional
integration of components, three -dimensional
architec tures, and nonlinear systems . The
main advantages of microfluidic systems include controllable flow of liquid, minimal
consumption of reagents or samples and
extremely fast analys is [2, 3]. Graphene is a
carbon family member and is one of the most
investigated materials in the recent years since
2004, when it was discovered [ 4]. It is called
the „wonder material” because of its excellent
thermal, optical, electronical and mechanica l
properties. Graphene is composed of a single
layer of carbon atoms in sp2 hybridization
arranged in a hexagonal honeycomb shape
with six -membered rings, forming two –
dimension (2 -D) crystals [8]. Graphene -based
biosensors may be integrated into microfluid ic
devices, and this brings many advantages,
including higher selectivity, sensitivity, real –
time measurement, rapid diagnosis,
multitarget analyses, automation, reduced
cost, and use of small sample volumes (10-9–
10-18L) [5 ]. Wu et al. reported a microfluidic
electroche mical chip with Ab and BSA onto
graphene for ultrasensitive multiplexed
determination of cancer biom arkers. The
channels cons isted of SU -8 patterns engraved
on chromatography paper by
photolitho graphy. The signal w as obtained
after the antibody –antigen binding by new
interactions with Abs anchored on horseradish
peroxidase (HRP) -coated silica nanoparticles.
The potential applicability of the device is the
ability to identify four candidate cancer
biomarkers [ 6]. Wan g et al have developed a

sensitive microfluidic device that isolates
circulating tumor cells (CTCs ) from breast
cancer patients. The device uses
functionalized Graphene Oxide (GO) and is
made of a gold patterned silicon dioxide
substrate bonded to a polydi methylsiloxane
(PDMS) top layer to form a microfluidic
chamber. The silicon dioxide substrates with
gold patterns were dipped in a solution that
has GO nanosheets functionalized with the
specific antibodies The GO increases the
surface area on which the sp ecific capture
tumor antibody is presented. 1 mL of sample
was used to analyze the protein or gene
expression patterns of CTCs. The CTC
enumeration is based on the expression of
CK+/DAPI+/CD45 -labeled cells. The chip
shows high sensitivity with reproducibi lity in
isolating CTCs. This noninvasive method has
the ability to classify CTCs based on their
gene expression and can supervise their
evolution over treatment course [ 7]. Karuwan
et al. presented a new method for mass
fabrication of a new microfluidic de vice with
integrated graphene -based electrochemical
electrodes by screen printing technique for in –
channel amperometric detection. A graphene
paste was used for subsequent screen printing
of electrodes on glass substrate. It gives a good
electrochemical response. The microfluidic
system has three parts: a PDMS microfluidic
structure, three -electrode amperometric
detection system fabricated on a glass
substrate by screen printing method. The third
part is given by the PDMS and glass chips that
were bonded to gether using oxygen plasma
treatment. [ 8].
In this paper we present a novel method to
transfer graphene films onto PDMS substrates
manufactured with microfluidic channel and it
is highlighted an excellent adhesion for further
applications , resulting in successful transfer
and improved stability of graphene film o n
microfluidic channel. Among the advantages
of the method, are included low fabrication
cost, high sensitivity, high throughput and
satisfactory reproducibility . The way the device is manufactured /
produced refers to how much it ultimately
costs.
2. Experimental
A. Materials and methods
The growth of graphene films was realized
in thermal CVD equipment – PlasmaPro100,
Nanofab 1000 model (Oxford Instruments)
dedicated to the growth processes of carbon
materials [9, 10] .
Graphene was synthesized on copper
catalyst by the Chemical Vapor Deposition
(CVD) – thermal method in a mixture of CH 4
and H 2 at an optimized temperature 1080˚ C.
The microchannel was manufactured in
PDMS substrate by soft lithography method .
Then, graphene obtained by CVD is
transferred on PDMS microchannel by wet
chemical method , based on Polymethyl –
methacrylate (PMMA) as a support layer .
The transfer process i s followed by an
oxygen plasma treatment o n the PDMS at a
power of 20 W for 20 sec. Oxygen plasma
treatment changed the surface property of
PDMS from hydrophobic to hydrophilic.
Raman Spectroscopy was used to ident ify
the vibrational modes of graphene mate rials.
For Raman spectroscopy, a high – resolution
Scanning Near -Field Optical Microscope
fitted with a Raman Module (Witec Alpha
300S) with 532 nm wavelength diode‐pumped
solid -state laser and maximum power
145 mW . The incident laser beam (a 1.0 µm
spot-size) was focused with a 100 x long
working distance microscope objective and
the spectra were collected with an exposure
time of 20s accumulation and
600 grooves/mm grating.
Optical Microscopy have been used to
investigate graphene layers integrated in
microfluidic channel .
B. Graphene integrated in microfluidics
Fig. 1 shows the scheme of the proposed
transfer method for the integration of SLG in
microfluidic channels.

Fig. 1 Overview of the graphene integration in
microfluidics platform

PMMA/graphene was dried out with the
PDMS substrate and as identified in the
optical microscopy image of Figure 2
graphene is a uniform c ontinuous film. To
remove PMMA, the PDMS substrate was
washed in acetone and then heat treated at 180
° C for 2 hours.

3. Results and discussions

Graphene was successfully transferred to
the microchannel made of PDMS . The
graphene film transferred to the microchannel
in PDMS adheres very well to the substrate, it
sticks very well, but remains suspended over
the channel without entering the
microchanne l.
Fig. 2 – Optical microscopy image with SLG
integrated in the microchannel made of PDMS
The Raman spectrum in Figure 3, taken
from the SLG sample transferred on the
PDMS microchannel, indicates the successful
transfer of the graphene monolayer, without
affecting its quality. However, following the
characterizations of optical microscopy and Raman spectroscopy, we observed the
presence of areas isolated with SLG, and it is
not found on the entire microchannel area. The
channels identify areas where SLG is
transferred to the microchannel, detected by
Raman Spectroscopy. Areas were identified
that descended into the microchannel, but also
areas where the SLG remained suspende d and
covered the microchannel, like a membrane.

Fig. 3- SLG Raman spectrum obtained by direct
transfer to the PDMS microchannel
The vibrational modes of graphene by the
presence of G (157 2.3 cm-1) and 2D (26 79.4
cm-1) bands specific to monolayer graphene
are present in the taken spectrum. The low
intensity of the D -band (13 37.6 cm-1) indicates
a good transfer, without introduced defects.
The I 2D/IG ratio ̴ 1.1 indicates a folding of the
graphene in the microchannel, an overlap
between the graphene domains.
The PDMS Raman spectrum comprises of
a Si–O–Si symmetric peak at 489.1 cm−1 and
a Si–C symmetric stretching at 709.7 cm−1.
The CH 3 stretch vibra tions exist at 2903.3 cm-
1 asym metric and 2961.8 cm-1 symmetric
stretch [11].
The final microfluidic device can be
visualized in Figure 4. It consists of 3 PDMS
layers, the first one is the sealing, the second
one has the microchannel and the transferred
graphene and the third layer contains the
microfluidic ports.
The current development of graphene
based microfluidic devices will be performed
in attaining point -of-care cancer diagnosis
throw light on the CTC capture and detection.

Fig. 4 – a) PDMS microfluidic device with
graphene b) Detail on the main microchannel with the
graphene transferred on the top side

4. Conclusions

In conclusion, this work has successfully
improved the processes of integrat ion of
graphene onto microfluidic channels . The O 2
plasma treatment significantly improves the
adhesion between the graphene layer and the
PDMS substrate which allows the transfer and
integrat ion of graphene successfully. The
results establish a great potential for the use of
graphene in the fabrication of transparent and
flexible devices with a high level of
complexity . A key role in the final selling
price of the device for cancer diagnosis is
played by the production process. The price of
a device reaches the amount of 70 EUR.

Acknowledgments . This work was
supported by UEFISCDI in the Partnership
Framework PN-III-P1–1.2-PCCDI -2017 0214
(Project No. 3PCCDI/2018) , TGE -PLAT
Project No.77/08.09.2016 SMIS code 2014+
105623, and by the European Social Fund
from the Sectoral Operational Programme
Human Capital 2014 -2020, through the
Financial Agreement with the title
“Scholarships for entrepreneurial education
among doct oral students and postdoctoral
researchers (Be Antreprenor!)”, Contract no.
51680/09.07.2019 – SMIS code: 124539.

Refer ences

[1] G.M. Whiteside, “The origins and the future of
microfluidics”, Nature, 442 (7101), 2006, pp.
368-373.
[2] Á. Ríos, M. Zougagh , M. Avila,
“Miniaturization through lab -on-a-chip: Utopia or reality for routine laboratories? A review”,
Analytica Chimica Acta 740, 2012, pp 1 – 11.
[3] Microfluidic devices in Nanotechnology:
Fundamental Concepts, Edited by Challa S.
Kumar, A Jhon Wiley & S ons, Inc.,
Publication, pp 2, 2010.
[4] A review on application of graphene -based
microfluidics, Xueye Chen, Shuai Zhang,
Wenbo Han, Zhongli Wu, Shouxin Wang .
[5] J. Sengupta, C. M. Hussain, “Graphene and its
derivatives for Analytical Lab on Chip
platforms”, Tren ds in Analytical Chemistry
(TrAC), Vol. 114, 2019, pp 326 -337.
[6] Y. Wu, P. Xue, Y. Kang, K.M. Hui, Paper –
based microfluidic electrochemical
immunodevice integrated with nanobioprobes
onto graphene film for ultrasensitive
multiplexed detection of cancer bioma rkers,
Anal. Chem. 85 (2013) 8661 –8668.
[7] T. H. Kim, H. J. Yoon, S. Fouladdel, Y. Wang,
M. Kozminsky, M. L. Burness, C. Paoletti, L.
Zhao, Eb. Azizi, S. Nagrath, “Characterizing
Circulating Tumor Cells Isolated from
Metastatic Breast Cancer Patients Using
Graphene Oxide Based Microfluidic Assay”,
Advanced Biosystems, Vol. 3 , Issue 2, 2018.
[8] Karuwan C, Wisitsoraat A, Chaisuwan P,
Nacapricha D and Tuantranont A, Screen –
printed graphene -based electrochemical
sensors for a microfluidic device. Anal
Methods 9:3689 –3695 (2017).
[9] B. Țîncu, A. Avram, M. Avram, V. Țucureanu,
A. Matei, C. Mărculescu, T. A. Burinaru, F.
Comănescu, I. Mihalache and I. Demetrescu,
“Investigation of graphene on quartz substrate”,
AIP Conference Proceedings, 2071(1), 2019.
[10] B. Tincu, I. Demetr escu, A. Avram, V.
Tucureanu, A. Matei, O. Tutunaru, T. Burinaru,
F. Comanescu, C. Voitincu, M. Avram,
“Performance of single layer graphene obtain
by chemical vapor deposition on gold
electrodes”, Diamond & Related Materials,
Vol. 98, 2019, 107510.
[11] D. Cai , A. Neyer, R. Kuckuk, M. Heise,
“Raman, mid -infrared, near -infrared and
ultraviolet –visible spectroscopy of PDMS
silicone rubber for characterization of polymer
optical waveguide materials”, Journal of
Molecular Structure, Vol. 976, 274 -281, 2010.