We report a pentacene thin-film transistor integrated with microfluidic channel as an ultrafast DNA sensor. The microchannel assisted in easy transport of sample onto the pentacene active layer. The DNA immobilization time on active layer was drastically shortened by applying low positive electric field at the gate electrode. This helps by attracting the negatively charged DNA toward the pentacene layer. This device was evaluated for the label-free detection of single stranded DNA. The electrical property of the device fiercely changed due to the adsorption of DNA. Furthermore, the electrical characteristics were studied as a function of immobilization voltage and time.