What The Doctor Ordered

Mass Flow Controlled Coating of Medical Devices

Advances in the design of medical devices such as catheters, guide wires and stents have greatly improved the quality of medical care. However, these devices are often made with materials that bring undesirable complications, such as bacterial infection, blood clots, and tissue trauma caused by device insertion. It is common to apply specialist coatings to alleviate these difficulties.

Coatings must be applied in a repeatable verifiable manner especially when the coating is an active drug product as for example in the case of a drug eluting stent.

Traditional coating technology involves the spraying of liquids using various types of nozzles, in all these applications the control of flow is vital to the accuracy of the coating applied.

By using traditional flow metering and pump control techniques flow-rates can be controlled to 5- 10% of the target rate. This may be acceptable in some applications, however where active drug substances are being applied a variation of 10% in drug coating leads to an unacceptable rate of failures & losses at the QC stage.

Responding to the need to improve flow control technology in low flow coating applications Bronkhorst Cori-Tech have developed a unique mini CORI-FLOW™ controlled pumping system which uses the Coriolis principle to accurately measure true mass flow rate.

Flow rates as low as 0.2 grams/hour can be controlled to an accuracy of 0.5% of target.

The mini CORI-FLOW™ controller uses its integral fast PID control system to adjust the speed of a closed loop coupled pump resulting in a typical dosing accuracy of 0.5-1%. This represents a 10 fold improvement in what is achievable using a traditional volume flow metering system.

The Bronkhorst mini CORI-FLOW™ measures mass flow directly and there is no need for the system to be calibrated for each liquid being pumped. It is not susceptible to errors caused by variations in density or temperature and is capable of controlling the flow of volatile fluids with low boiling points.

The system is configurable to your individual needs and is available with a wide variety of pumps, communication and control options.

Some applications where this technology can be of benefit include:

• Cardiac, peripheral and arterial stent coatings.
• Drug eluting balloon coatings.
• Pacemaker coatings.
• Coatings onto sutures and surgical instruments.
• Orthopedic implant coatings.
• Bio-absorbable and biocompatible coatings.
• Hydrophilic or hydrophobic coatings onto medical devices such as catheters.
• Guide wire coatings.
• Heparin and silicon coatings for blood collection tubes and syringes.
• Silver Silane coating onto bandages.
• Anti-microbial coatings onto medical textiles such as bandages, surgical gauze, gloves and masks.
• Microencapsulation of pharmaceuticals.
• Pharmaceutical spray drying.
• Coatings for diagnostic test kits.
• Protein, enzyme, and reagent coatings.
• Supercritical CO2 for creating drug-loaded nanophase material.

Not Vaporware

New Vapor Delivery Module

Bronkhorst High-Tech BV, manufacturer of mass flow meters and controllers for gases and liquids, designed a new series of Vapor Delivery Modules. These compact sub-systems incorporate a (thermal or Coriolis) liquid flow controller, one or two mass flow controllers for carrier gas and a temperature controlled mixing and evaporation device. The modules are equipped with a 1.8" TFT display and push-buttons for local readout and control. The systems can also be operated via digital communication (RS232 or FLOW-BUS). Optionally, the units can be supplied with an additional mass flow controller for dilution and with local or remote trace heating temperature control.

The compact, 'plug and work' modules can generate (saturated) vapor flows within the range of 100 sccm up to 10 SLM. The applied Controlled Evaporation Mixing (CEM) technology is suited for atmospheric or vacuum processes and is capable of evaporating mixtures and even solids, dissolved in solvents.

VDM-Series vaporizers are ideally suited for vapor deposition and coating processes for the production of semiconductor chips, displays and solar cells. The modules can also be applied for the calibration of analytical devices such as gas chromatographs and mass spectrometers, for anesthetic delivery, and for humidification of fuel cells.

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