Sensor device and method of using the same

A method of using a sensor device, comprising:

• providing a sensor device, comprising:
• a first substrate;
• a second substrate disposed opposite the first substrate;
• a flow channel disposed between the first substrate and the second substrate, the flow channel comprising a fluidic boundary;
• a first conductive layer disposed on the first substrate;
• a second conductive layer disposed on the second substrate;
• a first reaction group disposed on the first substrate, the first reaction group comprising a first reaction site, a second reaction site and a third reaction site, wherein the first reaction site is closer to the fluidic boundary than the second reaction site, and a size of the first reaction site is greater than or equal to a size of the second reaction site, and wherein the second reaction site is closer to the fluidic boundary than the third reaction site, and the size of the second reaction site is greater than a size of the third reaction site;
• loading a solution comprising the biosample into the flow channel;
• applying a voltage to the first conductive layer to immobilize the biosample on the first reaction group;
• turning off the voltage that is applied to the first conductive layer;
• and washing out excess biosample from the flow channel.