Method for thermally incubating an aqueous sample suspected to contain a target nucleic acid, the method comprising the steps of: a. providing a microfluidic chip comprising an inlet port in communication with a flow channel, wherein the flow channel is between an upper plate and a lower plate, the flow channel being in fluid connection with a plurality of reaction compartments on the inside wall of the upper plate and/or the lower plate, wherein the flow channel comprises a first material having a first affinity to the aqueous sample, and wherein the reaction compartments have a second affinity to the aqueous sample, and the second affinity is greater than the first affinity, wherein the microfluidic chip is preloaded with a sealing agent with a melting point above room temperature, wherein the sealing agent is a wax which is attached to an inner wall of the inlet port in solid state so as to not obstruct the passage of the aqueous sample or a displacement fluid through the inlet port into the flow channel; b. injecting the aqueous sample into the flow channel of the microfluidic chip through the inlet port and thereby dispensing the aqueous sample into the plurality of reaction compartments; c. injecting the displacement fluid into the flow channel of the microfluidic chip through the inlet port and thereby displacing the aqueous sample from the flow channel, thus fluidly separating the aqueous sample partitions within the individual reaction compartments from each other, wherein the displacement fluid is a silicone oil; d. melting the sealing agent with a melting point above room temperature in the inlet port of the microfluidic chip and subsequently allowing it to solidify at a temperature below its melting point so as to seal the inlet port; e. transferring the sealed microfluidic chip containing the aqueous sample partitions within the reaction compartments to a thermal incubation station; f. subjecting the microfluidic chip to a series of heating steps, wherein in one or more steps the melting temperature of the sealing agent is exceeded such that it is molten, thereby allowing for the exchange of gas and pressure equilibration through the inlet port; wherein the aqueous sample, the displacement fluid, and the sealing agent are immiscible with each other, and the sealing agent has a lower density than the aqueous sample. a. providing a microfluidic chip comprising an inlet port in communication with a flow channel, wherein the flow channel is between an upper plate and a lower plate, the flow channel being in fluid connection with a plurality of reaction compartments on the inside wall of the upper plate and/or the lower plate, wherein the flow channel comprises a first material having a first affinity to the aqueous sample, and wherein the reaction compartments have a second affinity to the aqueous sample, and the second affinity is greater than the first affinity, wherein the microfluidic chip is preloaded with a sealing agent with a melting point above room temperature, wherein the sealing agent is a wax which is attached to an inner wall of the inlet port in solid state so as to not obstruct the passage of the aqueous sample or a displacement fluid through the inlet port into the flow channel; b. injecting the aqueous sample into the flow channel of the microfluidic chip through the inlet port and thereby dispensing the aqueous sample into the plurality of reaction compartments; c. injecting the displacement fluid into the flow channel of the microfluidic chip through the inlet port and thereby displacing the aqueous sample from the flow channel, thus fluidly separating the aqueous sample partitions within the individual reaction compartments from each other, wherein the displacement fluid is a silicone oil; d. melting the sealing agent with a melting point above room temperature in the inlet port of the microfluidic chip and subsequently allowing it to solidify at a temperature below its melting point so as to seal the inlet port; e. transferring the sealed microfluidic chip containing the aqueous sample partitions within the reaction compartments to a thermal incubation station; f. subjecting the microfluidic chip to a series of heating steps, wherein in one or more steps the melting temperature of the sealing agent is exceeded such that it is molten, thereby allowing for the exchange of gas and pressure equilibration through the inlet port; wherein the aqueous sample, the displacement fluid, and the sealing agent are immiscible with each other, and the sealing agent has a lower density than the aqueous sample.