Investigation of Laser-Carbon Nanotubes Interaction and Development of CNT-Based Devices

Abstract

Interactions between laser and carbon nanotubes (CNTs) were investigated with a focused laser beam system. Phenomena of sustained laser-induced incandescence (LII) and laser-induced actuation were observed and studied. Bright and sustained LII of CNTs was achieved by irradiating a continuous wave focused laser beam on CNTs that are subjected to moderate vacuum. The sustained incandescence originated from radiative dissipation of heated CNTs due to laser-CNT interactions. Numerical fittings of the LII intensity spectrum with Planck blackbody distribution indicate a rise of temperature from room temperature to ~2500 K in less than 0.1 s. Through a systematic study of the effect of vacuum level and gaseous environment on LII, the process of thermal runaway during LII in CNTs was discovered. Post-LII craters with well-defined ring boundaries in the CNT array were observed and examined. Enhanced purity of CNTs after LII as indicated by Raman spectroscopy studies was attributed to the removal of amorphous carbons on the as-grown CNTs during LII. Laser-induced rapid actuating microstructures made of aligned carbon nanotube (CNT) arrays are achieved. Desirable operational features of the CNT micro-actuators include low laser power activation, rapid response, elastic and reversible motion, and robust durability. Experimental evidence suggests a laser-induced electrostatic interaction mechanism as the primary cause of the optomechanical phenomenon. Oscillating CNT micro-actuators up to 40 kHz are achieved by driving them with a modulated laser beam. The detailed studies of the above phenomena laid the groundwork for future applications of laser-CNTs interactions. LII provides an effective way of achieving rapid high temperature heating at specific localized positions within CNT arrays. LII can also be used to increase the heat resilience of CNTs. The CNTs micro-actuators are utilized in exerting a sub-micro-Newton force to bend nanowires. Electrical coupling of the micro-actuator and feasibilities of multiactuator systems made entirely out of CNTs are also demonstrated.