Working Principle of Micro Pump
A micro pump refers to a miniaturized fluid delivery device with small flow rates (μL/min to mL/min scale) and compact size. Its core function is to convert non-fluid energy (electric, piezoelectric, magnetic, thermal, mechanical vibration) into fluid kinetic energy to drive liquid/gas flow. Classified by driving mechanisms, mainstream types and their principles are as follows:
1. Piezoelectric Micro Pump (Most Widely Used)
Core Principle
Utilizes the inverse piezoelectric effect: Piezoelectric ceramics deform rapidly when applied alternating voltage, generating reciprocating vibration.
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Alternating current triggers the piezoelectric diaphragm to bend up and down periodically, expanding and shrinking the pump chamber volume.
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Suction stroke: Diaphragm pulls upward → chamber volume increases, internal pressure drops, inlet one-way valve opens, fluid is sucked into the cavity; outlet valve closes to prevent backflow.
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Discharge stroke: Diaphragm presses downward → chamber volume shrinks, pressure rises, outlet valve opens, fluid is extruded outward; inlet valve closes to avoid fluid reflux.
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High-frequency reciprocating vibration realizes continuous tiny-volume fluid transportation.
Advantages: Ultra-small size, low power, precise micro-flow control, silent operation.
Typical Scenarios: Medical infusion, lab microfluidics, inkjet printing, SCR urea micro pumps.
2. Electromagnetic Diaphragm Micro Pump
Core Principle
Relies on electromagnetic attraction to drive diaphragm reciprocation.
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After power-on, the coil generates a magnetic field, pulling the magnetic metal sheet attached to the diaphragm to compress the pump chamber.
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Power cut off, the built-in spring resets the diaphragm, expanding the chamber.
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Paired with two one-way check valves, periodic volume change completes suction and drainage circulation.
Features: Larger flow than piezoelectric pumps, simple structure, low cost, used for small-scale liquid circulation.
3. Peristaltic Micro Pump
Core Principle
Simulates intestinal peristalsis via mechanical extrusion.
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Multiple rotating rollers sequentially squeeze a flexible micro silicone tube.
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The squeezed tube segment closes and pushes fluid forward; the rear tube rebounds to form negative pressure and absorb new fluid.
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Rotation speed directly controls flow volume, no contact between pump body and medium.
Advantages: Zero contamination, easy tube replacement; Disadvantage: Slight flow pulsation.
Application: Laboratory reagent transfer, biological sample delivery.
4. Thermal Bubble Micro Pump (Thermopneumatic Type)
Core Principle
Thermal expansion of gas bubbles drives fluid flow.
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A micro heating resistor inside the cavity heats the fluid instantly to generate tiny vapor bubbles.
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Bubble expansion raises cavity pressure to push fluid out; after power off, bubbles cool and shrink to form negative pressure for liquid suction.
Features: No moving mechanical parts, ultra-miniaturized chip integration; Mainly used in microfluidic chips, portable biosensors.
5. Electroosmotic Micro Pump (No Mechanical Moving Parts)
Core Principle
Based on electroosmosis effect in microchannels.
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The inner wall of the tiny flow channel adsorbs charged ions to form an electric double layer.
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Apply DC voltage at both ends of the channel, free counterions in the liquid move directionally under the electric field, dragging the entire fluid to flow.
Advantages: Completely silent, precise nanoliter-level flow regulation; Limited to low-conductivity buffer solutions for biochemical chips.
General Core Common Logic of All Micro Pumps
Nearly all mechanical micro pumps follow the same basic fluid logic:
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Periodically change the volume of a sealed micro-cavity to produce alternating negative pressure (suction) and positive pressure (discharge);
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Cooperate with one-way valves or directional channel structures to unify fluid flow direction, avoiding backflow;
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Miniaturize cavity, diaphragm and drive components to achieve microliter-level accurate fluid output.
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