Valve for controlling flow of a fluid

Abstract

A valve for controlling flow of a primary fluid in a primary flow channel comprises a valve fluid channel, and a membrane of a porous dielectric material located in the channel so as to divide the channel into an inlet part and an outlet part and so that valve fluid flowing between the inlet and outlet parts flows through the said membrane. First and second electrodes are located for electrical communication with valve fluid in the inlet and outlet parts respectively of the valve fluid channel for application of an electric potential across the membrane in order to promote electro-osmotic flow of valve fluid through the membrane. A valve member can be displaced between open and closed positions as a result of valve fluid moving in the valve fluid channel through the membrane, into or out of the outlet part of the valve fluid channel, in which the valve member causes a reduction in the capacity for flow of the primary fluid in the primary flow channel when it is in the closed position compared with when it is in the open position.

Description

CROSS-REFERENCED RELATED APPLICATIONS [0001] This application is a continuation of prior application Ser. No. 10 / 651,835, filed Aug. 29, 2003. This invention relates to a valve for controlling flow of a fluid in a flow channel, and to a pump for controlling flow of a fluid in a flow channel.BACKGROUND OF THE INVENTION [0002] The flow of fluids through conduits can be controlled using components such as pumps and valves. Pumps and valves can operate to control parameters such as flow rate; adjustment of relative flow rates of constituents in a mixture can be used to vary the composition of the mixture. [0003] Accurate control of flow of a fluid can be important in many medical applications, for example in drug delivery and in the modulation of body fluid drainage. Devices in which flow control is important include pumps for dispensing drugs such as insulin and opiates, and hydrocephalus shunts for drainage of spinal fluids. [0004] Accurate control over the flow of drugs and fluids in...

AI Technical Summary

Benefits of technology

[0016] The valve fluid can include at least one additive to control the pH of the fluid. The valve fluid can include at least one additive to control the ionic strength of the fluid. Additives should preferably dissolve completely in the fluid. The kind and concentration of additives should preferably be such as to enhance or to optimise the zeta potential under the conditions imposed by the size of the pores in the porous dielectric medium.

[0017] The degree of ionization of the surface sites depends on the pH of the fluid. In most cases there is a pH at which the surface is net neutral and hence the zeta potential is zero. The zeta potential reaches a maximum value for pH values significantly above (for acidic surface sites) or pH values significantly below (for basic surface sites) the pH value at which the surface is net neutral. Ionisable surface sites can be added to a material by chemical reaction or grafting, or induced by creation of reactive surface chemistry or creation of defects via plasma or radiation treatment.

[0018] Examples of fluids which can be used in the valve fluid include water, cyclic carbonates, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, benzyl alcohol, nitromethane, nitrobenzene, butanone, dimethoxymethane, dimethylacetamide, dioxane, p-dioxane, acetonitrile, formamide, tetrahydrofuran, dimethyl formamide, acetone, acetic acid, triethylamine, dichloromethane, ethylene glycol, dimethylsulphoxide, ammonium acetate.

[0019] The valve fluid can include additives which can affect the zeta potential. Ionic species can have the opposite charge sign to the zeta potential. Ionic species can have the same charge sign as the zeta potential. Preferably, ionic species which are included in the valve fluid

Problems solved by technology

However, once implanted, the rate of flow of drug

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