Electrical current for controlling fluid parameters in microchannels

A method of heating fluid in a microfluidic system, said method comprising steps of;

• providing a channel having a first end, a second end, and a region defined therebetween, said channel being disposed in a substrate;
• providing fluid in said region of said channel;
• applying an electric current through said fluid to heat said fluid at said region;
• wherein said electric current selectively heats said fluid in said region of said channel while preventing substantial heating of said fluid outside said region.

A method of controlling temperature of fluid in a channel defined in a substrate of a microfluidic system, said method comprising steps of:

• applying an electrical energy source to begin heating said fluid in said channel;
• and
• adjusting a first parameter applied from said electrical energy source to said fluid to provide a relatively constant second parameter in said fluid, wherein said first parameter is current, voltage, power or a combination thereof, and the second parameter is resistance and conductivity;
• and
• wherein said fluid is heated without substantially increasing a temperature of said substrate.