The package design for microfluidic sensors is discussed. The MicroElectroMechanical Systems (MEMS) device covered in this paper requires a fluidic and electrical interface as well as vacuum packaging of the sensing element. By using a by-pass package design the limitations of low flow rate and high pressure drop often encountered with microfluidic products can be avoided. The MEMS device utilizes a resonating silicon microtube that is electrostatically driven and capacitively sensed. A platinum RTD is also integrated into the MEMS chip. To improve the Q of the resonator a thin-film getter has been integrated to lower the microcavity pressure. The microfluidic packaging technology lends itself to producing densitometers, chemical concentration meters and Coriolis mass flow sensors. The device has been applied to fuel cell concentration sensors for embedded Direct Methanol Fuel Cell (DMFC) systems. The DMFC systems require a methanol sensor to minimize crossover and hence optimize the water/methanol concentration over temperature and the life of the product. Other high flow rate applications include ethanol/gasoline concentration sensors for E85 vehicles and dialysis fluid monitoring. A microfluidic Coriolis mass flow sensor has been developed and applied to drug delivery to monitor the drug dose, total volume infused, drug type and concentration. Chemical and temperature compatibility of the MEMS chip and packaging materials must be considered when dealing with this wide range of applications and will be discussed in the paper.

1.
F.Jiang and Y.Tai, Theoretical and experimental studies of micromachined hot-wire anemometers,” IEDM, IEEE, (1994) 6.4.1–6.4.4.
2.
Oosterbroek
R.
et al.,
A micromachined pressure/flow sensor
,
Sensors & Actuators
,
77
(
1999
)
167
177
.
3.
Enoksson
P.
,
Stemme
G.
and
Stemme
E.
,
A silicon resonant sensor structure for Coriolis mass-flow measurements
,
J. MEMS
,
6
(
1997
)
119
125
.
4.
Corman
T.
,
Enoksson
P.
,
Noren
K.
and
Stemme
G.
,
A low-pressure encapsulated resonant fluid density sensor with feedback control
,
Meas. Sci. Tech.
,
11
(
2000
)
205
211
.
5.
S. Lee, X. Wang, W. Shin, Z. Xiao, K. Chin and K. Farmer, Simulation and modeling of a bridge-type resonant beam for a Coriolis true mass flow sensor, Nanotech 2004, (2004).
6.
Y. Zhang, S. Tadigadapa and N. Najafi, A micromachined Coriolis-force-based mass flowmeter for direct mass flow and fluid density measurements, Transducers’01, (2001) 1460–1463.
7.
S.Tadigadapa, C.Tsai, Y.Zhang and N.Najafi, Micromachined fluidic apparatus, US Patent 6,477,901, (2002).
8.
D.Sparks, R.Smith, S.Massoud-Ansari, N,Najafi, Coriolis mass flow, density and temperature sensing with a single vacuum sealed MEMS chip, Solid-State Sensors and Actuator, and Microsystem Workshop, Hilton Head, SC, June (2004) 75–78.
9.
Henmi
H.
,
Shoji
S.
,
Shoji
Y.
,
Yoshimi
K.
and
Esashi
M.
,
Vacuum packaging for microsensors by glass-silicon anodic bonding
,
Sensor and Actuators A
,
43
, (
1994
)
243
249
.
10.
Sparks
D.
, et al.,
Wafer-to-wafer bonding of nonplanarized MEMS surfaces using solder
,
J. Micromech.&Microengr.
,
11
, (
6)
, (
2001
)
630
635
.
11.
Sparks
D.
,
Massoud-Ansari
S.
,
Najafi
N.
,
Chip-level vacuum packaging of micromachines using vnanogetters
,
IEEE Trans. Adv. Packaging
,
26
(
3)
(
2003
)
277
281
.
12.
Sparks
D.
,
Smith
R.
,
Straayer
M.
,
Cripe
J.
,
Schneider
R.
,
Chimbayo
A.
,
Ansari
S.
,
Najafi
N.
,
Measurement of density and chemical concentration using a microfluidic chip
,
Lab Chip
,
3
(
2003
)
19
21
.
13.
D.Sparks, N.Najafi, R.Smith, Improving drug infusion safety with a microfluidic sensor, Proc. 11th Annual FDA Science Forum, G-20, (2005) 72.
14.
FDA, 510(k), No. K050783, ISSYS Drug Flow Monitor, 21 CFR 880.2420, Feb 22, (2006).
15.
D.Sparks, D.Bihary, D.Goetzinger, N.Najafi, K.Kawaguchi and M.Yasuda, “Methanol concentration sensors for DMFCs,” Small Fuel Cells 2006, The Knowledge Foundation, Washington DC, March, (2006) 606–630.
16.
Cruickshank
J.
and
Scott
K.
, “
The degree and effect of methanol crossover in the direct methanol fuel cell
,”
J. Power Sources
, Vol.
70
, (
1998
)
40
47
.
17.
K.Varde & C.Clarke, “A comparison of burn characteristics and exhaust emissions from off-highway engines fueled by E0 and E85,” SAE 2004-28-0045, (2004).
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