The xxpress Direct Resistive Heating System
By using the xxplate consumable as the resistive heating element in a very low voltage circuit, we can direct and deliver precise amounts of heat. xxplates are available in 24, 54, and 96 well formats, they are completely interchangeable requiring no hardware modification. The system for heating uses a number of discrete power supplies to pass currents through the xxplate via a number of different routes, thus giving multi-zone heating control and ensuring heat is delivered precisely where it is required.
Figure 1. Power Supply Configuration
Figure 2. One of the many combinations for applying current and thus heating specific plate areas.
This effect can be visualised using thermal imaging technology:
Figure 3. Thermal image of plate showing heated areas
This heating and cooling is under the control of a complex algorithm. To deliver the temperature response required the control algorithm decides which heating pattern to use and the amount of heat to be generated. This measurement, calculation and heating cycle happens 100 times per second and the system delivers a thermal accuracy and uniformity of ± 0.3°C.
The revolutionary xxpress®
In conventional block cyclers using Peltier effect devices, the primary limitation on performance is the 200-500 micron thick walls of the sample tube or microtitre plate separating the samples from the heat source. There are however a number of additional thermal barriers.
When the xxplate cross section is compared to a “conventional” peltier block the differences become apparent. The peltier device pumps heat to the electrical junction between two materials. This heat then has to pass through a ceramic plate, into a metal base plate, then up a metal well form, then through the polypropylene consumable, to reach the liquid assay. It is this inherent disconnect between temperature creation and sample that cause the “limits” that constrain these systems.
|Channel||Excitation (nm)||Emission (nm)||Common Dyes|
|Channel 1||Blue||470||513-531||FAM/SYBR Green|
|Channel 3||Amber||590||600-617||ROX/Texas Red|
|Channel 4||Red||627||662-685||Cy 5|
|Channel 5||Red||627||694-734||Cy 5.5|