We present a microfluidic impedance device for achieving both the flow ratio sensing and the conductivity difference detection between sample stream and reference buffer. By using a flow focusing configuration, with the core flow having a higher conductivity sample than the sheath flow streams, the conductance of the device varies linearly with the flow ratio, with R2 > 0.999. On the other hand, by using deionized (DI)-water sheath flow as a reference, we can detect the difference in conductivity between the buffer of core flow and sheath DI-water with a high detection sensitivity of up to 1 nM of sodium chloride solution. Our study provides a promising approach for on-chip flow mixing characterization and bacteria detection.

1.
J.
Suehiro
,
R.
Yatsunami
,
R.
Hamada
, and
M.
Hara
,
J. Phys. D: Appl. Phys.
32
,
2814
(
1999
).
2.
J.
Suehiro
,
D.
Noutomi
,
M.
Shutou
, and
M.
Hara
,
J. Electrost.
58
,
229
246
(
2003
).
3.
J. B. Y.
Koh
and
Marcos
,
Electrophoresis
36
,
1514
1521
(
2015
).
4.
N. P.
Tran
and
Marcos
,
Electrophoresis
36
,
1485
1492
(
2015
).
5.
J.
Collins
and
A. P.
Lee
,
Lab Chip
4
,
7
10
(
2004
).
6.
C.
Yang
,
D.
Hu
,
B.
Sun
,
X.
Cui
,
Q.
Zhu
, and
R. H. W.
Lam
,
Microfluid. Nanofluid.
19
,
711
720
(
2015
).
7.
J.
Chen
,
C.
Xue
,
Y.
Zhao
,
D.
Chen
,
M.-H.
Wu
, and
J.
Wang
,
Int. J. Mol. Sci.
16
,
9804
9830
(
2015
).
8.
M.
Kim
,
T.
Jung
,
Y.
Kim
,
C.
Lee
,
K.
Woo
,
J. H.
Seol
, and
S.
Yang
,
Biosens. Bioelectron.
74
,
1011
1015
(
2015
).
9.
T. F.
Kong
and
N.-T.
Nguyen
,
Microsyst. Technol.
21
,
519
526
(
2015
).
10.
C.
Páez-Avilés
,
E.
Juanola-Feliu
,
J.
Punter-Villagrasa
,
B.
del Moral Zamora
,
A.
Homs-Corbera
,
J.
Colomer-Farrarons
,
P. L.
Miribel-Català
, and
J.
Samitier
,
Sensors
16
,
1514
(
2016
).
11.
R. H. W.
Lam
,
X.
Cui
,
W.
Guo
, and
T.
Thorsen
,
Lab Chip
16
,
1652
1662
(
2016
).
12.
Q. D.
Tran
,
T. F.
Kong
,
D.
Hu
,
Marcos
, and
R. H. W.
Lam
,
Lab Chip
16
,
2813
2819
(
2016
).
13.
Marcos
,
N. P.
Tran
,
A. R.
Saini
,
K. C. H.
Ong
, and
W. J.
Chia
,
Microfluid. Nanofluid.
17
,
809
819
(
2014
).
14.
T. F.
Kong
,
W.
Ye
,
W. K.
Peng
,
H.
Wei Hou
,
Marcos
,
P. R.
Preiser
,
N.-T.
Nguyen
, and
J.
Han
,
Sci. Rep.
5
,
11425
(
2015
).
15.
X.
Cheng
,
Y.-S.
Liu
,
D.
Irimia
,
U.
Demirci
,
L.
Yang
,
L.
Zamir
,
W. R.
Rodriguez
,
M.
Toner
, and
R.
Bashir
,
Lab Chip
7
,
746
755
(
2007
).
16.
S. C. C.
Shih
,
B.-N.
Irena
,
X.
Yang
,
R.
Fobel
, and
A. R.
Wheeler
,
Biosens. Bioelectron.
42
,
314
320
(
2013
).
17.
P.
Ertl
,
C. A.
Emrich
,
P.
Singhal
, and
R. A.
Mathies
,
Anal. Chem.
76
,
3749
3755
(
2004
).
18.
R. H. W.
Lam
,
Adv. Rob. Autom.
3
,
1000e119
(
2013
).
19.
J.
Zhu
and
X.
Xuan
,
Electrophoresis
30
,
2668
2675
(
2009
).
20.
D.
Chen
,
H.
Du
, and
W.
Li
,
Sens. Actuators, A
133
,
329
334
(
2007
).
21.
J.
Guo
and
Y.
Kang
, “
Capacitance-based microfluidic sensors
,” in
Encyclopedia of Microfluidics and Nanofluidics
, edited by
D.
Li
(
Springer US
,
Boston, MA
,
2013
), pp.
1
9
.
22.
S. G.
Dastider
,
S.
Barizuddin
,
N. S.
Yuksek
,
M.
Dweik
, and
M. F.
Almasri
,
J. Sens.
2015
,
293461
.
23.
Z.
Zou
,
J.
Kai
,
M. J.
Rust
,
J.
Han
, and
C. H.
Ahn
,
Sens. Actuators, A
136
,
518
526
(
2007
).
24.
J. D.
Ramshaw
,
J. Chem. Phys.
55
,
1763
1774
(
1971
).
25.
Marcos
,
C.
Yang
,
T. N.
Wong
, and
K. T.
Ooi
,
Int. J. Eng. Sci.
42
,
1459
1481
(
2004
).
26.
Marcos
,
K. T.
Ooi
,
C.
Yang
,
J. C.
Chai
, and
T. N.
Wong
,
Int. J. Eng. Sci.
43
,
1349
1362
(
2005
).
27.
Marcos
,
Y. J.
Kang
,
K. T.
Ooi
,
C.
Yang
, and
T. N.
Wong
,
J. Micromech. Microeng.
15
,
301
312
(
2005
).
28.
C.
Zhao
and
C.
Yang
,
Microfluid. Nanofluid.
13
,
179
203
(
2012
).
29.
P. V.
Gerwen
,
W.
Laureyn
,
W.
Laureys
,
G.
Huyberechts
,
M. O. D.
Beeck
,
K.
Baert
,
J.
Suls
,
W.
Sansen
,
P.
Jacobs
,
L.
Hermans
, and
R.
Mertens
,
Sens. Actuator, B
49
,
73
80
(
1998
).
30.
G. H.
Markx
,
P. A.
Dyda
, and
R.
Pethig
,
J. Biotechnol.
51
,
175
180
(
1996
).
31.
J.
Suehiro
,
T.
Hatano
,
M.
Shutou
, and
M.
Hara
,
Sens. Actuator, B
109
,
209
215
(
2005
).

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