Ultrasonic nanoimprint on engineering plastics

The authors developed a new ultrasonic nanoimprint technology that is superior to the current thermal and UV nanoimprint technologies. In the new technology an ultrasonic vibration is impressed along the direction of the loading force during a molding operation at room temperature. The mold in this case is mounted onto an ultrasonic generator with a UV photoresist, where the mold patterns are pushed and pulled on a thermoplastic material at a high speed by employing ultrasonic vibration. The system employs a magnetostriction actuator that generates ultrasonic vibration with frequencies and amplitudes ranging from dc to 20 kHz and from 0 to +/- 3 mu m, respectively. Several optimized imprinting conditions had been investigated by using polyethylene terephthalate (T(g)=69 degrees C) with a comparatively low glass transition temperature in engineering plastics. These optimized imprinting conditions were found to be frequency of the ultrasonic vibration=10 kHz, amplitude=3 mu m, contact force=500 N, contact time=60 s, and buffer material=polyurethane rubber. Then under those optimized molding conditions, other engineering plastics were successfully imprinted. The depth of the imprinted pattern was found to decrease as the glass transition temperature of the plastic rose. The assisting effect of the ultrasonic vibration was found to be inversely proportional to the glass transition temperature.