Nanopores, which are tiny openings in a membrane so small that only a single DNA strand or virus particle can pass through, are an exciting new platform for building sensors. A direct measurement of the thermal effects caused by these ions can help make nanopores more practical as sensors.
A team of researchers has created a thermocouple made of gold and platinum nanowires with a point of contact just 100 nm in size that served as the thermometer. It was used to measure the temperature directly next to a nanopore cut into a 40-nm-thick film suspended on a silicon wafer.
Joule heating occurs when electrical energy is converted into heat by the resistance in a wire. When studying a 300-nm-sized nanopore, the researchers recorded the ionic current of a phosphate buffered saline as a function of applied voltage. They demonstrated nearly ohmic behavior over a wide range of experimental conditions.
With smaller nanopores, the heating effect became more pronounced, because less fluid from the cooler side could pass through to equalize the temperature. As a result, the heating could cause a non-negligible effect, with nanopores experiencing a temperature increase of a few degrees under standard operating conditions.
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