Device and associated methods for detecting a property of a fluid. The device includes a body region and a first flexible element having a first end and a second end. The first end is fixedly located on the body region. The flexible element includes at least a first layer having a first coefficient of thermal expansion and a second layer having a second, different coefficient of thermal expansion. An electrical heater element can be arranged to heat the flexible element to induce bending of said flexible element. The resistance of a first portion of the electrical heater element adjacent the first end can be greater than the resistance of a second portion of the electrical heater element further from the first end. The device can include a heater controller arranged to supply an electrical pulse having a duration less than 5 ms to the electrical heater. The device can include a second, reference flexible element having a first end and a second end, with the first end fixedly located on the body region. Each flexible element can include a respective sensor arranged to provide a signal indicative of the movement of that flexible element. The sensor of the reference flexible element has a different configuration than the sensor of the first flexible element, with at least one of the flexible elements including at least one additional portion of material for equalizing the thermal conductivity distribution of the two flexible elements.