Analog DNA circuit does math in a test tube. Duke Today, Aug. 23, 2016. Duke University researchers have created strands of synthetic DNA that, when mixed together in a test tube in the right concentrations, form an analog circuit that can add, subtract and multiply as the molecules form and break bonds. While most DNA circuits are digital, their device performs calculations in an analog fashion by measuring the varying concentrations of specific DNA molecules directly, without requiring special circuitry to convert them to zeroes and ones first. Picked up by NPR affiliate WFDD.