The xxpress® NGx 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 1. Power Supply Configuration

Figure 2 One of the many combinations for applying current and thus heating specific plate areas.

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

Figure 3. Thermal image of plate showing heated areas

Cooling of the consumable is by means of several individually controlled air jets giving multi-zone control of cooling too.

Temperature measurements are made using an array of non-contact Infrared temperature sensors.

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® NGx

  • The xxplate is a single-use consumable that is, in itself, a complex, multi-zone heating element.
  • Heating accuracy of the sample is further enhanced by the key feature that, within the xxplate the liquid samples are separated from the temperature controlled surface, only by a polymer layer 10µm thick.

Figure 4. Diagrammatic representation of a cross section through the xxplate ® showing the intimate relationship between the plate and sample temperatures.

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.

Figure 5. A “conventional” peltier block

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.

  • There are 5 exciting LED wavelengths, each with its own blocking filter, each paired with a specific wavelength band pass filter, mounted on a filter wheel in front of the camera. Each channel may be used in isolation or may be part of a multiplexing combination.
  • This enables the most popularly used fluorophores to be excited and detected by the xxpress® cycler. The emitted fluorescence is detected by a CCD camera. Each LED has a band blocking filter in front of it. The blocked wavelengths being those that would pass through a particular band pass filter in front of the camera. So, when the exciting LED is turned on, the camera cannot “see” reflected radiation from the LED, but can “see” emitted light from the fluorophore.
  • Fluorescence measurements are made through the transparent polyester sealing film over the tops of the wells. The second function of the camera is to detect whether a 96, 54, or 24 well consumable has been inserted, and to detect its orientation.

  • Up to 5 PCR cycles per minute with fluorescence measurement every cycle.
  • 10°C per second thermal ramp rate in the sample, throughout the run.
  • 24, 54 and 96 well plates in a standard format that are interchangeable. No need to change anything.
  • 24 well 5 – 40 µL fill
  • 54 well 2 – 15 µL fill
  • 96 well 1 – 5 µL fill
  • This allows for optimal reagent use and minimises costs: see how much you could save.
  • Dimensions: width – 300mm, height – 320mm, depth – 590mm
Channel Excitation (nm) Emission (nm) Common Dyes
Channel 1 Green 474 507-527 FAM/SYBR Green
Channel 2 Yellow 535 567-583 JOE/VIC/HEX/TAM
Channel 3 Amber 578 617-633 ROX/Texas Red
Channel 4 Red 635 667-679 Cy 5
Channel 5 Deep Red 662 698-724 Cy 5.5