Our client wanted to retain market leadership in molecular diagnostics. Our brief was to design its new optical and thermal polymerase chain reaction (PCR) module to provide much faster real-time PCR cycling. Faster cycling means less time per molecular diagnostic, more patients tested in one hospital shift, with happy hospitals and renewed contracts. And for us in the public, ‘faster’ here also means ‘cheaper’ diagnostics and monitoring of cancer and HIV patients.
This was a substantial design project, where we had to employ strong mathematical modelling to simulate PCR temperature cycling, as well as models for ‘signal chain’ to ensure the signal-to-noise ratio matched the request for low-cost optics.
Emphasis at the start was on the control strategy for rapid thermal cycling. The design implemented thermoelectric coolers (TECs), with tightly controlled thermal ramping. The design involved thermal and computational fluid dynamics (CFD) modelling of reaction vessels, thermal heat sinks and TECs, as well as novel algorithms and electronics for thermal control.
The novel thermal algorithms allow tightly controlled ramping up and down of the temperature on the reaction vessels. The improvement in thermal control results in stronger signals from the sample and dyes, and increased sensitivity.
Good thermal control also allows for multiplexed PCR menus across the samples, even if closely placed within the instrument. That gives much increased flexibility to the menu of tests done simultaneously. The design is completed by a low-cost multichannel optical read head, specified for the client’s dyes, that works around the space left by the TECs and thermal mass.
We provided prototypes ready for validation within 12 months of the start of the project. Our new design has led to a sixfold increase in the speed of reverse transcription PCR – speeding up the diagnosis of patients in hospitals across the world, and helping with account retention for our client.