PUMA actuator12

www.fh-jena.de/~feller/
Development of a pulsation-free pump for microfluidic analysis
K. L. Hoffmeier, M. Schimmelpfennig, D. Hoffmann, K.-H. Feller
Introduction
Many fluidic applications in chemical engineering, biotechnology and medical technology require a constant and
pulsation free flow, for example for time stable mixing processes. Our aim is to develop small affordable pumps that
provide such a continuous pulsation-free flow. These pumps operate on the principle of the peristaltic pump. The
novelty is the actuation of several pumping chambers by a specific control algorithm, ensuring a continuous flow at the
in- and outlet. Since the volume within the pump is time independent and at any stage the same, cyclic processes
(short-circuit operation) can easily be realized without additional compensation devices.
To create a linear peristaltic pump we arranged 5 pumping chambers in a row, in which the third pumping chamber has
a volume of at least three times that of the other chambers. The pumping chambers are formed by pistons acting on a
silicone hose or a specially developed pumping chip for small volumes.
Theoretical flow schedule. The numbers
visualize the normalized volume.
Additional information is available at patent
application WO002010118740A2
Material & Methods
2,5
0,15
stroke [mm]
ejected mass [g]
As cost-efficient actuator we use a camshaft. The flow schedule of each pumping chamber is controlled by the specific cam profiles.
The stroke-flow characteristic of each chamber was first characterized by unloading (squeezing) the camber with a constant stroke rate while measuring
the outflow. Subsequently, the derived stroke-flow data were transformed to linearized flow, resulting in nonlinear stroke rates. These resulting stroke
rates were mapped on specially designed cams.
0,10
0,05
0,00
0
1
2
3
stroke [mm]
silicone hose
experimental model
of a single pumping
camber
specific stroke-flow
characteristic of a single
chamber
2,0
1,5
1,0
0,5
0,0
0
30
60
90
120
angle [°]
transformed stroke
pattern for linearized flow
designed cam,
comprising the stroke
pattern
linear peristaltic pump, the design of
each cam was generated as described
before
To refine the interaction of the pumping chambers, we then replaced the camshaft by 5 custom made linear actuators and developed a LabView
program for synchronous visualization of the flow profile at the pump outlet and the control of the corresponding stroke pattern of the pumping
cambers. Finally, the in this way refined stroke pattern can be used to create optimized cams.
detailed view of the custom made linear actuator
DC motor
(Maxon)
front end of the used LabView program, the stroke
pattern of the actuators can be adjusted by sliders
linear ball bushings
(Bosch Rexroth)
screw drive
(MiSUMi)
optimized cams
inductive limit switches
(Baumer)
flow-sensor
FLOW
Summary
Although the pumping concept is quite simple, the clue is in the camshaft. Each hose or chip has its own specific stroke-flow characteristic which has to
be addressed with specific cams. For ideal pulsation-free flow the interaction of the 5 pumping chambers has to be optimized empirically.
Our design covers flow rates of 0.1 to 20 ml/min with the hose and 10 to 2,000 µl/min with the chip.
Contact: [email protected]
Funding: The Study was supported by the German Federal Ministry of
Economy and Technology BMWi within the ZIM Program