Choosing a Pump for your Fluid Handling Application
The type of pump you choose for your fluid handling will largely depend on your laboratory application. In this article, we will compare the popular pump types.
A peristaltic pump has a series of rollers that rotate around the edge of the pump head. A flexible tubing is threaded around the rollers and pressed up tight next to them, pinching the tubing where it contacts a roller. As the rollers rotate around the head, the fluid in the tubing moves from the input to the output. The rate of head rotation and the size of the tubing determine the volume of fluid that can be pumped. The volume that can be pumped is limited only by the volume of the input source.
A syringe pump consists of a syringe attached to a motor driven pusher block which is usually driven by a stepper motor that moves in distinct increments. The syringe is filled with liquid and placed into the pump. As the pusher block moves, it presses the plunger of the syringe, which ejects the fluid. Some of these pumps can be programmed to allow for precise control. A variety of syringe pumps are available.
- Infusion/withdrawal (I/W) describes the syringe pump feature where the syringe plunger is held by the pusher so the motor can pull the plunger back, withdrawing fluid, as well as push the plunger to infuse it.
- A push/pull syringe pumps uses two syringes mounted back to back so movement of the pusher block simultaneously withdraws fluid into one syringe and infuses an equal amount from the other.
Pneumatic pumps use air pressure to move liquid in a micropipette or channel. The air behind the fluid in the pipette or channel moves the fluid. The pump uses a solenoid valve (electronic/mechanical switch) to control the flow of air. The pump consists of a regulator to control the pressure, a pressure gauge, an electronically controlled solenoid valve and a timer. These pumps are typically used for very small volumes in the picoliter to nanoliter range. The volume injected is controlled by the glass tip inside diameter (ID), pressure and time using the equation PV=nRT. Pressure (pascals) times volume (m3) equals the amount of gas (moles) times a constant times temperature (Kelvin).
Microfluidic pumps are designed to handle small volumes and work in a non-pulsatile way.
Pump Type Comparison