Ultrasensitive thermometer for atmospheric pressure operation based on a micromechanical resonator

• A high frequency micromechanical resonator is used as a temperature sensor operating at atmospheric pressure.
• Thanks to the high Q-factor in air a resolution of 3 mK is shown.
• The temperature sensitivity is measured at different relative humidity values and it varies up to 50%.
• The desorption of water molecules from the resonator surface is monitored with a resolution of 0.007 water molecules per nm2 (∼1/140 of a water monolayer).

For highly integrated systems for bio and chemical analysis a precise and integrated measurement of temperature is of fundamental importance. We have developed an ultrasensitive thermometer based on a micromechanical resonator for operation in air. The high quality factor and the strong temperature dependence of the resonance frequency of these bulk microresonators enable accurate temperature measurements. Here, we delineate the conditions to decouple the temperature effect on the resonance frequency, from the water adsorption/desorption on the resonator surface that happens when it is operated in air. This study enables high temperature resolution measurements, as well as the possibility of monitoring adsorption and desorption processes on the resonator surface with a resolution of 0.007 water molecules per nm2. These devices reach a temperature resolution of 3 mK in air, which is one of the best ever reported temperature resolution for resonator based thermometers.