A thermal management device enabling PCR reactions in a microfluidic channel, the device comprising: a framework; two or more thermal zone sub-assemblies coupled to the framework, each thermal zone sub-assembly having a thermal control element, and wherein each thermal zone sub-assembly is coupled to the framework by one or more thermal actuation mechanisms; one or more thermal spreaders configured to contact the thermal control elements of the two or more thermal zone sub-assemblies; and a flexible heater circuit configured and arranged to be the thermal control element for two or more thermal zone sub-assemblies of the thermal management device, wherein the thermal actuation mechanisms comprise insulative bearings, fasteners, and a spring, wherein the spring is configured to apply a force to drive the thermal control element toward one of the one or more thermal spreaders, wherein each fastener is a shoulder screw, wherein each thermal actuation mechanisms includes at least one insulative bearing, which travels up and down on the shaft of at least one of the shoulder screws that are attached to the framework and are pushed by the spring, and wherein a first region of the flexible heater circuit is configured to be moved by one of the thermal actuation mechanisms to be in contact with one of the thermal spreaders, and wherein the first region of the flexible heater circuit is in contact with one of the thermal spreaders, at least a second region of the flexible heater circuit is in contact with another one of the thermal spreaders, and the first region of the flexible heater circuit and the second region of the flexible heater circuit are connected by tabs configured to allow each zone to move independently when driven by the respective thermal actuation mechanisms, so that the first and second regions can move relative to each other a distance of up to 0.75 mm to 1.0 mm. a framework; two or more thermal zone sub-assemblies coupled to the framework, each thermal zone sub-assembly having a thermal control element, and wherein each thermal zone sub-assembly is coupled to the framework by one or more thermal actuation mechanisms; one or more thermal spreaders configured to contact the thermal control elements of the two or more thermal zone sub-assemblies; and a flexible heater circuit configured and arranged to be the thermal control element for two or more thermal zone sub-assemblies of the thermal management device, wherein the thermal actuation mechanisms comprise insulative bearings, fasteners, and a spring, wherein the spring is configured to apply a force to drive the thermal control element toward one of the one or more thermal spreaders, wherein each fastener is a shoulder screw, wherein each thermal actuation mechanisms includes at least one insulative bearing, which travels up and down on the shaft of at least one of the shoulder screws that are attached to the framework and are pushed by the spring, and wherein a first region of the flexible heater circuit is configured to be moved by one of the thermal actuation mechanisms to be in contact with one of the thermal spreaders, and wherein the first region of the flexible heater circuit is in contact with one of the thermal spreaders, at least a second region of the flexible heater circuit is in contact with another one of the thermal spreaders, and the first region of the flexible heater circuit and the second region of the flexible heater circuit are connected by tabs configured to allow each zone to move independently when driven by the respective thermal actuation mechanisms, so that the first and second regions can move relative to each other a distance of up to 0.75 mm to 1.0 mm.