We demonstrate a method for high-bandwidth, high-sensitivity particle sensing and cell counting in a microfluidic system. Our approach employs a tuned radiofrequency probe, which forms the radiofrequency analog of a Coulter counter. By measuring the reflected rf power, this approach provides an unprecedented detection rate, with a theoretical bandwidth in excess of 10 MHz. Particle detection was performed in a continuous flow mode in a microfluidic channel, using 15μm diameter polystyrene beads suspended in a sucrose-saline solution. We demonstrate 30 kHz counting rates and show high-resolution bead time-of-flight data, comprising the fastest electronic particle detection on-chip to date.

1.
W. H.
Coulter
, U. S. Patent No. 2,656,508 (
1953
).
2.
A. G.
Tibbe
,
B. G.
de Grooth
,
J.
Greve
,
G. J.
Dolan
,
C.
Rao
, and
L. W.
Terstappen
,
Cytometry
47
,
163
(
2002
).
3.
S.
Gawad
,
K.
Cheung
,
U.
Seger
,
A.
Bertsch
, and
P.
Renaud
,
Lab Chip
4
,
241
(
2004
).
4.
M.
Berger
,
J.
Castelino
,
R.
Huang
,
M.
Shah
, and
R. H.
Austin
,
Electrophoresis
22
,
3883
(
2001
).
5.
M.
Dürr
,
J.
Kentsch
,
T.
Müller
,
T.
Schnelle
, and
M.
Stelzle
,
Electrophoresis
24
,
722
(
2003
).
6.
M. M.
Wang
,
E.
Tu
,
D. E.
Raymond
,
J. M.
Yang
,
H.
Zhang
,
N.
Hagen
,
B.
Dees
,
E. M.
Mercer
,
A. H.
Forster
,
P. J.
Marchand
, and
W. F.
Butler
,
Nat. Biotechnol.
23
,
83
(
2005
).
7.
S.
Gawad
,
L.
Schild
, and
P.
Renaud
,
Lab Chip
1
,
76
(
2001
).
8.
L. L.
Sohn
,
O. A.
Saleh
,
G. R.
Facer
,
A. J.
Beavis
,
R. S.
Allan
, and
D. A.
Notterman
,
PNAS
97
,
10687
(
2000
).
9.
G. R.
Facer
,
D. A.
Notterman
, and
L. L.
Sohn
,
Appl. Phys. Lett.
78
,
996
(
2001
).
10.
R. J.
Schoelkopf
,
P.
Wahlgren
,
A. A.
Kozhevnikov
,
P.
Delsing
, and
D. E.
Prober
,
Science
280
,
1238
(
1998
).
11.
D. R.
Schmidt
,
C. S.
Yung
, and
A. N.
Cleland
,
Appl. Phys. Lett.
83
,
1002
(
2003
).
12.
D. R.
Schmidt
,
C. S.
Yung
, and
A. N.
Cleland
,
Phys. Rev. B
69
,
140301
(
2004
).
13.
Sylgard 184
,
Dow-Corning Inc.
14.
Y.
Xia
,
E.
Kim
,
X.-M.
Zhao
,
J. A.
Rogers
,
M.
Prentiss
, and
G. M.
Whitesides
,
Science
273
,
347
(
1996
).
15.

Phosphate buffered saline concentrate, Sigma-Aldrich Co. Working 1× solution contains 10 mM sodium phosphate and 0.9 wt% sodium chloride in water.

16.
Bangs Laboratories, Inc.
, Fishers, IN.
17.
Harvard Apparatus
, Holliston, MA.
18.
M.
Spiga
and
G. L.
Morino
,
Int. Commun. Heat Mass Transfer
21
,
469
(
1994
).
19.
S. F.
Ibrahim
and
G.
van den Engh
,
Curr. Opin. Biotechnol.
14
,
5
(
2003
).
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