Patent Application
20080061429
The general principle of the invention is shown in
Common to the embodiments described above is that the heat transfer elements are oriented in a fan-like manner such that the footprint of the elements at a distance from the base plate is larger than the footprint of the elements near the area of contact of the elements and the base plate. More generally, it can also be said that the heat transfer elements of the heat sink are preferably oriented in a non-parallel configuration such that the heat dissipation capacity of the heat sink is spatially essentially evenly distributed across the base plate so as to minimize variations in passive heat transfer through the thermoelectric element during heating and cooling of the sample holder. Non-parallelity of the protruding portions of the heat sink compensates for the limited size of the base plate (and the peltier module) and causes the temperature of the upper side of the base plate to remain at even temperature. Thus, no “hot spot” is formed in the middle portion of the base plate, such as in some prior art solutions.
The spacing between the neighboring heat transfer elements is thus typically increasing when moved away from the base plate, i.e., there is a considareble angle between neighboring elements. The angle can also be non-constant in along the length of the elements. Also when viewed in the plane of the base plate, the angle may vary between different element pairs. In addition or alternatively the heat transfer elements may be initially non-uniformly pitched to the base plate. Both described methods have an effect on the spatial heat dissipation capacity of the sink.
The heat transfer elements can have the form of fins, fin pins, straight plates, pleated plates, or any other solid member in the form of an extended surface experiencing energy transfer by conduction within its boundaries, as well as energy transfer with its surroundings by convection and/or radiation, used to enhance heat transfer by increasing surface area.
The heat sink can be made of many different materials including aluminum, copper, silver, magnesium, silicon carbide and others, either singly or in combination. It also can be fabricated by any common method of manufacturing heat sinks, including extrusion, casting, machining, or fabrication techniques, either in entirety or in combination with simple finishing via machining. Most advantageously, the heat sink consists of a single continuous (unitary) piece. The even heat distribution is achieved solely by the proper alignment of the heat transfer elements, whereby there is typically no need for separate heat diffusion blocks, heat conductor arrangements or additional active heaters or coolers.
The thermoelement used in connection with the present heat sink is preferably a peltier unit comprising one or more individual peltier modules. Multiple peltier modules may be driven in parallel without individual temperature control.
The sample holder may be of any known type. Typically it is fabricated from aluminium or comparable metal and is shaped to accommodate microtiter plates according to SBS standards (Society for Biomolecular Screening). Thus, on the top surface of the holder, there are a plurality of wells arranged in a grid. The bottoms of the wells are formed to tightly fit against the outer walls of the microtiter plates so as to provide good thermal connection between the holder and the plate. In a preferred embodiment, a sample holder designed for v-bottomed (or u-bottomed) plates is used.
Preferably, the footprints of the thermoelement and the base plate of the heat sink are essentially equal. Thus, no increased heat flow takes place at the lateral portions of the heat sink (cf.
According to a preferred embodiment of the invention, a fan directed to the heat rejection zone (i.e., between the heat transfer elements) of the heat sink is used during cycling. This significantly increases the energy transfer rate from the heat sink to the ambient air.
According to a further embodiment, the device according to the invention is a lightweight portable thermal cycler, possibly operated by a battery. Such a device can be used in field circumstances, i.e., where the biological samples to be analyzed are in the fast place. In field circumstances, the benefits provided by the heat sink at hand, i.e., compact and simple form and low energy consumption, are emphasized.
The invention may also be used in connection with other solutions for increasing thermal uniformity or efficiency of thermal cyclers, for example those referred to as prior art in this document However, it has been found that shaping of the heat sink according to the invention is usually sufficient for practically eliminating the temperature non-uniformity caused b conventional heat sinks and thermal cyclers.
Many different configurations are possible within the scope of this invention, including variations on part geometries, methods of assemblies and configurations of parts relative to each other. The description here is meant to illustrate and represent some possible embodiments of the invention.
The invention in not limited to the embodiments presented above in the description and drawings, but it may vary within the full scope of the following claims. The embodiments defined in the dependent claims, and in the description above, may be freely combined.
