A roller-ball pen enabled direct writing electronics via room temperature
liquid metal ink was proposed. With the rolling to print mechanism, the
metallic inks were smoothly written on flexible polymer substrate to form
conductive tracks and electronic devices. The contact angle analyzer and
scanning electron microscope were implemented to probe the inner property of
the obtained electronics. An ever high writing resolution with line width and
thickness as 200{\mu}m and 80{\mu}m, respectively was realized. Further, with
the administration of external writing pressure, GaIn24.5 droplets embody
increasing wettability on polymer which demonstrates the pervasive adaptability
of the roller-ball pen electronics