Microfluidic pump with thermal control

A method of cooling a fluid being conveyed through a microfluidic pump, the microfluidic pump having a series of resistive heaters disposed along a substrate in an elongate conduit carrying the fluid, a temperature sensor in thermal communication with the substrate, and a firing signal generator in communication with the temperature sensor and the resistive heaters, and at least one additional resistive heater in thermal communication with the substrate, the method comprising:

• producing a firing signal containing energy to activate the series of resistive heaters, the firing signal producing a series of periodic firing pulse sequences, each firing pulse sequence consisting essentially of a number of firing pulses, successive firing pulses being separated by an idle period comprising a period of time with no firing pulses;
• activating at least some of the series of resistive heaters from one resistive heater to a next resistive heater using the firing signal to heat the fluid such that the fluid moves through the elongate conduit;
• measuring a pump temperature using the temperature sensor;
• reducing the energy supplied by the firing signal when the pump temperature is above a selected temperature limit;
• and
• supplying a modulated signal to activate the additional resistive heater and heat the substrate until the pump temperature reaches a selected minimum temperature.

A microfluidic pump comprising:

• a substrate defining a covered elongate conduit for carrying a fluid and having a rate of heat dissipation;
• a series of resistive heaters disposed along the covered elongate conduit, wherein activating the resistive heaters in series from one resistive heater to a next resistive heater using a firing pulse sequence moves the fluid through the elongate conduit in a direction and at a speed based on the firing pulse sequence;
• a temperature sensor in thermal communication with the substrate, the temperature sensor measuring a pump temperature and producing a temperature signal corresponding to the pump temperature;
• and
• a fire signal generator in electrical communication with each resistive heater, the fire signal generator producing a series of firing pulse sequences, each firing pulse sequence consisting essentially of a number of firing pulses, successive firing pulses being separated by an idle period comprising a period of time with no firing pulses, the fire signal generator reducing the energy in the firing pulse sequence when the pump temperature is above a temperature limit.