Applicator with thermal contact sensors

A method of thermal contact detection, comprising:

• applying to a skin of a subject an applicator containing a thermal contact sensor that comprises:
• a metal frame;
• a can-like housing having housing walls and a bottom which is thinner than the housing walls;
• at least one temperature sensor and a heater;
• and
• a flexible printed circuit board including enhanced solder coated pads configured to receive the at least one temperature sensor and the heater;
• operating the thermal contact sensor in one of a first mode, a second mode and a third mode to determine whether the thermal contact sensor is in contact with the skin of the subject;
• wherein operating the thermal contact sensor in the first mode comprises operating the heater to maintain a temperature difference between the skin and the metal frame;
• wherein operating the thermal contact sensor in the second mode comprises measuring power supplied to the thermal contact sensor;
• and
• wherein operating the thermal contact sensor in the third mode comprises measuring a difference in a thermal inertia of the thermal contact sensor in an idle state and in contact with the skin, comprising:
• heating the can-like housing with the heater;
• measuring the time it takes the heater to raise the temperature of the thermal contact sensor from 15° C. to 38° C.;
• if the elapsed time it takes the heater to raise the temperature of the thermal contact sensor is less than 400 msec, determining that there is no contact of the thermal contact sensor with the skin;
• and
• if the elapsed time it takes the heater to raise the temperature of the thermal contact sensor is more than 600 msec, determining that there is a contact of the thermal contact sensor with the skin.