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Patent Application Review

The invention relates to a microfluidic switch for stopping a liquid flow for a period of time comprising a switch with at least one first channel, at least one second channel, a common area where the paths of the first and second channels meet, and a stopping mechanism at the end of the first channel. An example of an embodiment of the microfluidic switch is provided below. As can be seen, the switch is shown by 20, the first channel by 3 and the second channel by 4.    

There are three independent claims for the invention. The first claim (i.e. claim 1) is directed to a microfluidic switch which covers all the eight embodiments described in the specification. As long as a switch comprises two channels with the first channel comprising a stopping mechanism and a second channel for continuing the flow in the first channel, it falls within the scope of the present invention. The dependent claims (i.e. claims 2 to 22) further define the microfluidic switch according to the embodiments provided in the invention.

The final product may then be removed from the reaction chamber in order to be analyzed. The stopping means for well known microfluidic arrangements are usually made as mechanical valves, which are initiated and controlled from the outside. These valves are used to separate individual reaction chambers and analysis chambers one from the other by using fluids.  External time control, for example via a computer, the corresponding incubation times, i.e. the time intervals of the residence of the sample or products in the reaction chambers and/or analysis chambers, can be adjusted. These microfluidic switches with microvalves have the property that they have mechanically moving parts, which for example are accordingly electrically triggered. This leads to high hardware complexity. In addition, integration of these microvalves into the microfluidic switches is complex, especially when the microfluidic switch is made of plastic. This allows the microfluidic to be more useful than the current available methods.

To summarise, although the microfluidic switch of the present invention may be considered patentable for it is considered novel and inventive, it appears that the cons in its use outweighs the pros and as such it may not be considered as an efficient means of regulating the flow of liquid in a microfluidic channel and creating a time interval for a reaction to take place. In particular, due to the presence of many variants (i.e. the viscosity of the liquid to be used, the length of the second channel, the contours of the second channel, and the size of the reaction chamber) that affect the functionality and efficiency of the microfluidic switch, it causes the switch to complicate the process instead of simplifying it. Further, in order to get the appropriate time interval, all these factors have to be considered and many tests have to be carried out varying these factors before the perfect combination can be determined. Therefore, it appears that the use of the microfluidic switch in stopping the liquid flow at the end of the first channel for a predetermined time interval without the need for electrically triggerable microvalves to restart the liquid flow may not be the best way of regulating the flow of the liquid.

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