Micro-calorimeter apparatus

A biosensor system comprising:

• a pair of essentially flat heat sinks (9,10), arranged with their surfaces facing each other, each heat sink being a circular plate formed from a material having a large heat capacity;
• a pair of Peltier elements (11) thermally attached to said heat sinks (9,10), one element (11) on each heat sink (9,10), on said facing surfaces, each heat sink/Peltier forming a unit;
• and
• a thermostated compartment (3,4,5),
• the heat sinks (9,10) being suspended inside said compartment (3,4,5) by heat insulating members (8a,8b;160) connected to a respective block (3,4;80,100) so as to form an air gap between the heat sinks (9,10), whereby the heat sinks (9, 10) thermally float such that heat exchange between the heat sink and the thermostated compartment (3,4,5) is kept minimal, wherein
• there is a gap between the Peltier elements (11) in which gap an insertable, generally flat biosensor unit (12) is positioned and fits snugly,
• said biosensor unit (12) comprising a reaction chamber in which a reaction is to be run, the heat of reaction of which can be measured by said Peltier elements, wherein
• the biosensor unit comprises thin foils (20;340) defining opposite walls of said reaction chamber (14;300) defined by the biosensor unit (12;260), a thickness of the reaction chamber being small in relation to dimensions of walls defined by the foils, the thickness being in an interval of 0.3-0.5 mm, and wherein the Peltier elements (11;200) are arranged so as to be in a heat conducting contact with said thin foils when the biosensor unit (12;260) is in an operative position between the Peltier elements (11;200),
• the heat conducting contact area between Peltier elements (11;200) and the foils (20;340) corresponds to the total reaction chamber wall area defined by said foils (20;340), and
• the heat sinks are thermally insulated from their immediate environment so as to provide uniform heat flow from the reaction chamber (14;300) to the heat sinks,
• wherein a heat capacity of the heat sinks is selected such that a thermal impact from a heat flow in the heat sinks creates a thermal disturbance of an order of <1-100 ppm.