Fluid handling – Flow affected by fluid contact – energy field or coanda effect – Means to regulate or vary operation of device
Reexamination Certificate
2001-07-05
2003-01-21
Chambers, A. Michael (Department: 3753)
Fluid handling
Flow affected by fluid contact, energy field or coanda effect
Means to regulate or vary operation of device
C137S807000, C137S833000, C204S454000, C204S601000
Reexamination Certificate
active
06508273
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for controlling a liquid flow in a liquid channel. The present invention also relates to an assembly and integrated circuit in which this device is placed, and to a method for manufacture thereof.
2. Description of the Prior Art
Charged particles in a solution or suspension of liquid channel con be transported by applying an electric field substantially parallel to the liquid channel. Under the influence of the electric field positively and negatively charged particles will move in opposing directions. This transport is also referred to as electrophoresis.
Another mechanism for generating a liquid flow in a liquid channel is formed by so-called electro-osmosis. The liquid channel is in this case enclosed by an electric insulator. At the location of the transition between the insulator and the liquid are situated charged insulator particles which are chemically bound to the insulator. As a consequence of the charge of these insulator particles, particles with an opposing charge are formed close to the insulator wall in the liquid channel. The layer consisting of the chemically bound insulator particles and the liquid particles charged in opposing directions is also referred to as the electric double layer. As a result of the presence of these particles with opposing charge, which are not chemically bound to the insulator, and the above mentioned electric field applied parallel to the direction of the liquid channel, a liquid flow will be generated along the walls of the liquid channel. The liquid flow along the walls brings about a liquid flow across the entire diameter of the liquid channel as a result of the friction between the liquid particles.
The moving charged particles define a shear plane at some distance of the insulator wall. The electrical potential at the location of this shear plane is called the &zgr;-potential (Zeta potential). The magnitude of the &zgr;-potential depends inter alia on factors such as the type of liquid or insulator, the concentrations of the different particles in the liquid, the pH value and the like. The direction and the degree of liquid flow resulting from electro-osmosis can be controlled by changing these factors.
It can be deemed known to vary the potential of the outer surface of the insulator with a voltage source, as a result of which the above stated &zgr;-potential in the liquid channel can be varied. Since the direction and speed of the liquid flow in the liquid channel depends on the magnitude of the &zgr;-potential, the movement of the particles in the liquid can be controlled with the voltage source, i.e. the movement of particles resulting from electrophoresis can be enhanced or decreased. While there are indeed devices known which enable such a control of the liquid flow in a liquid channel, they have large dimensions and require very high control voltages in the order of magnitude of several kVs, so that in practice they cannot be integrated with standard electronic components such as transistors, integrated circuits and so on.
The object of the present invention is to obviate these drawbacks.
SUMMARY OF THE INVENTION
According to an aspect of the invention, a device is provided for this purpose for controlling a liquid flow in a liquid channel, comprising:
an elongate liquid holder in which a liquid channel is provided in longitudinal direction;
first voltage means for applying a first voltage difference over substantially the longitudinal direction of the liquid channel;
a conductor member arranged in at least a part of the liquid channel against the liquid holder;
an insulator member arranged in the liquid channel against at least the conductor member;
second voltage means for providing a second voltage difference between the conductor member and the liquid in the liquid channel; wherein the thickness of the insulator member is a maximum of 1 &mgr;m and preferably in the order of magnitude of some tens of nanometres. In accordance with this aspect of the invention a device is therefore provided for controlling a liquid flow, wherein the functions of liquid container or liquid holder on the one hand and of insulator or &zgr;-potential control layer on the other are separated, so that a great flexibility can be achieved in choice of material and method of manufacture.
According to a preferred embodiment of the invention the insulator member is formed from a thin layer or coating of insulator material, the conductor member and the liquid holder are combined and formed from a mechanically stable conductor material. The mechanically stable material provides in this case the required sturdiness of the device.
According to a further preferred embodiment of the invention the insulator member and the conductor member are formed from thin layers of respectively insulator material and conductor material, wherein the liquid holder is preferably formed from a mechanically stable material.
According to another aspect of the invention, a device is provided for controlling the liquid flow in a liquid channel, comprising:
an insulator member which defines an elongate liquid channel;
first voltage means for applying a first voltage difference over substantially the longitudinal direction of the liquid channel;
a conductor member arranged over at least a part of the outer surface of the insulator member;
second voltage means for providing a second voltage difference between the conductor member and the liquid in the liquid channel; wherein the distance between the outer surface and the inner surface of the insulator member is a maximum of 1 &mgr;m and preferably in the order of magnitude of some tens of nanometres. By making the wall thickness of the insulator member so small, the control of the liquid flow can advantageously be performed with a small second voltage difference, for instance with a voltage difference of less than 20 Volt. At such small wall thicknesses there moreover occurs a reduced loss of power and an improved heat discharge is possible.
According to a further preferred embodiment of the invention the device can be directly connected to standard electronic elements or integrated circuits or can even be integrated therewith. This preferred embodiment can therefore be advantageously connected directly onto and controlled by the output of the standard electronic elements such as integrated circuits, without additional provisions being required therein.
According to a further preferred embodiment of the invention the insulator member and the conductor member are manufactured from optically transparent materials. This has the advantage that the content and/or composition of the content of the liquid channel can be optically detected in simple manner.
According to a further preferred embodiment of the invention the insulator member is constructed from two or more insulator part-members manufactured with materials of different &zgr;-potential. This has the advantage that various flows with differing speeds and directions can be generated in the liquid channel without applying an external potential difference.
According to a further embodiment of the invention the insulator member is provided with two or more conductor members, to which mutually differing voltages can be applied. By applying different potentials to the conductor members, the associated &zgr;-potentials in the liquid channel will accordingly differ from each other. This has the advantage that different flows with differing speeds and/or directions of movement can be generated within the same liquid channel.
According to another preferred embodiment the voltage means comprise two electrodes which are arranged in the liquid channel. Because the electrodes can be arranged in the liquid the distance between the electrodes can be reduced, at least relative to the distance in the case of external electrodes, to an order of magnitude of a few-micrometers. Lower voltages are hereby sufficient to obtain the desired field strength of the electric field.
According to a further asp
Chambers A. Michael
Universiteit Twente (Mesa Research Instituut)
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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