Micropump

More recently, efforts have been made to design non-mechanical micropumps that are functional in remote locations due to their non-dependence on external power.

The driving force can be generated by utilizing piezoelectric,[13] electrostatic, thermo-pneumatic, pneumatic or magnetic effects.

Non-mechanical pumps function with electro-hydrodynamic, electro-osmotic, electrochemical [14] or ultrasonic flow generation, just to name a few of the actuation mechanisms that are currently studied.

Piezoelectric driven micropumps rely on electromechanical property of piezo ceramic to deform in response to applied voltage.

Piezoelectric disk attached to the membrane causes diaphragm deflection driven by the external axial electric field thus expanding and contracting the chamber of the micropump.

[9] The smallest piezoelectric micropump with dimensions of 3.5x3.5x0.6 mm3 was developed by Fraunhofer EMFT[17] the world-renowned research organization with focus on MEMS and Microsystem technologies.

While positive voltage vice versa drives the diaphragm down, which results in overpressure opening outlet valve and forcing the fluid out of the chamber.

Currently mechanical micropump technology extensively uses Silicon and Glass based micromachining processes for fabrication.

[16] Silicon micromachining has numerous advantages that facilitate the technology widespread in high performance applications as, for example, in drug delivery.

[9] Thus, silicon micromachining allows high geometric precision and long-term stability, since mechanically moving parts, e.g. valve flaps, do not exhibit wear and fatigue.

Gas bubbles within chamber hinder micropump operation as due to the damping properties of the gas bubbles the pressure peaks (∆P) in the pump chamber decreases, while due to the surface properties the critical pressure (∆Pcrit) that opens passive valves increases.

[19] The compression ratio of Fraunhofer EMFT micropumps reaches the value of 1, which implies self-priming capability and bubble tolerance even at challenging outlet pressure conditions.

Considerable reduction of the dead volume resulted from predeflected actuators along with shallow fabricated pump chamber heights increases the compression ratio.

These three valves are opened and closed sequentially in order to pull fluid from the inlet to the outlet in a process known as peristalsis.

Bio-inspired applications include a flexible electromagnetic micropump using magnetorheological elastomer to replace lymphatic vessels.

Thanks to MEMS fabrication technology, gas sensors based on MOS, NDIR, electrochemical principles could be miniaturized to fit portable devices as well as smartphones and wearables.

Application of the Fraunhofer EMFT piezoelectric micropump reduces reaction time of the sensor up to 2 seconds through fast sampling of the ambient air.

Micropump can advance remote diagnostic and monitoring of gastrointestinal tract and pulmonary diseases, diabetes, cancer etc.

Piezoelectric MEMS micropumps can replace traditional peristaltic or syringe pumps for intravenous, subcutaneous, arterial, ocular drug injection.

[16] Due to biocompatibility and miniature size, silicon piezoelectric micropump can be implanted on the eyeball to treat glaucoma or phthisis.

Artificial sphincter technology based on the titanium micropump ensures continence by automatically adjusting the pressure during laughter or coughing.