(Currently under development)

CONCEPT

The MIP device is the most sophisticated generation of a family of piezo-actuated silicon micropumps developed by DEBIOTECH for drug delivery applications. This high performance pumping mechanism has been conceived to be the heart of a programmable implantable drug infusion system. A MEMS (Micro-Electro-Mechanical System) approach was adopted focusing on the aspects of miniaturization, safety, reliability and accuracy. The result is a high-performance micropump with a low flow rate range of typically 1 m l/min. Due to the versatility of the technology and the design approach, it should also meet the requirements of a variety of liquid micro-dosing applications wherever high performance is to be guaranteed over the lifetime of the product.

DESIGN

The working principle is a volumetric pump with pumping membrane, which compresses a chamber in a reciprocating movement and which is associated to a pair of check valves in order to direct the liquid flow.
The chip is a stack of four layers bonded together : two (purple) silicon plates with micromachined pump structures and two (dark blue) glass pieces with through-holes. Added to the stack is a piezoelectric ceramic disc (green), responsible for the actuation and two titanium fluid connectors (gray), hermetically joined to the chip.

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DESIGN FEATURES

Double limiter concept

A constant and accurate flow rate is guaranteed through the control of the span of the pumping membrane. Consequently, the flow rate is linear with actuation frequency and virtually insensitive to inlet and outlet pressure, actuation voltage, temperature, viscosity and aging.

High compression ratio

The fluidic path is designed to minimize dead volume. Thanks to the resulting high compression ratio, the pump is self-priming and tolerant to small air bubbles.

On-chip particle filter

In order to protect the sensitive elements and to ensure a long-term leak-free functioning of the pump, a fine filter is integrated on-chip.

Functional detector

The outlet valve can be equipped with contacts allowing the detection of occlusion and the presence of air.

Hermetic connection to titanium

A proprietary titanium-to-pyrex joining technique was developed in order to provide the pump chip with weldable hermetic titanium fluid connectors.

Biocompatible materials

The materials in contact with the drug are only Silicon, Silicon-dioxide, Pyrex glass, and Titanium.

TECHNOLOGY

The manufacture of this device relies essentially on standard silicon bulk micromachining and anodic wafer bonding. The overall wafer processing is a 12 mask process.

Silicon micromachining is a generic, widespread and non-proprietary technology. It is supported by the powerful semi-conductor industry. Therefore, the technology for this device is widely available and easily transferable, while protected by numerous patents. Most of the front-end technology (wafer-processing) has been successfully transferred to a semi-industrial fab line. Several runs have been processed, achieving a yield >90%. More than 100 pumps of the last generation have been produced and tested.

Plot of the stroke volume dependence as a function of inlet and outlet pressure. This shows that the stroke volume, and in turn the flow rate, are virtually independent of outlet and inlet pressures. This outstanding characteristic is achieved through the combined benefits of the double limiter and the compensated outlet valve.

Plot of the flow rate stability at 0.05Hz for more than 2 ½ months (permanent acquisition). Note that rough aspect of the curve is mainly due to the sensitivity of the measurement setup to the daily temperature variations.