|
|
|
|
|
|
|
Stack Valve
(by Dr. Daniel C. S. Bien)
|
|
This
section presents a novel micromachined
passive valve for fluid
flow control within microfluidic systems. Forward flow
through the valve is in the opposite direction to other
published designs and the valve is thus of considerable
potential in integrated microfluidic devices or systems. The
valve has been designed in such a way that it opens when a
polysilicon plate is deflected towards the silicon
substrate. The valve closes when the plate is deflected away
from the substrate and against an upper polysilicon closure
bridge.
A
schematic view of the microvalve is shown in Figure 1.
The top layer (Poly 2) forms the valve closure bridge
containing a square inlet aperture. The middle layer (Poly
1) consists of a movable valve plate supported by four
flexible arms; fluid can flow through passages around these
arms during operation. The bottom or substrate layer
provides the outlet port surrounded by four pillars which
act as end-stops when the movable plate is deflected
downwards. The top two layers are are anchored to the
silicon substrate layer at the outer edges of the device. |
|
|
|
 |
|
Figure 2. Optical image |
|
 |
|
Figure 3. FIB cross-section |
|
|
Figure 1.
Schematic view of the stack microvalve |
|
Fabricated valves were characterised for fluid flow
under forward and reverse pressure. A forward flow of
1920 ml/min was obtained at forward pressure of 14.1 kPa.
In the reverse direction, the flow rate is limited to
less than 8 ml/min, thus giving a forward to reverse
flow rate ratio of 240:1. |
 |
 |
|
Forward flow characteristics |
Reverse flow characteristics |
|
References
-
Bien DCS , Mitchell SJN and Gamble
HS, “Fabrication of
characterisation of a novel microvalve for microfluidic
applications”, SPIE Journal of Microlithography,
Microfabrication and Microsystems, vol. 3, no. 3, July
2004.
-
Bien
DCS,
Mitchell SJN,
Gamble HS and
Fitzgerald
SP, Passive
Microvalve, European Patent Application, EP1296607,
2002.
|
|
|
