Photo-Induced Crawling Motion of Azobenzene Crystals on Modified Gold Surfaces

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Investigating photo-induced motion of molecular crystals is crucial for developing advanced micro-devices.
• Understanding how surface properties influence crystal movement is key to controlling nanoscale transport.

Purpose of the Study:

• To study the photo-induced crawling motion of 3,3 -dimethylazobenzene (DMAB) crystals on various gold surfaces.
• To determine the impact of surface properties and patterns on DMAB crystal locomotion.
• To provide insights for designing surface-driven micro-transport systems.

Main Methods:

• Fabrication of gold surfaces with different functionalized thiol treatments (hydroxyl-terminated and alkyl-terminated).
• Creation of patterned substrates with alternating surface chemistries and topographical features.
• Observation and analysis of DMAB crystal crawling motion under simultaneous UV and visible light irradiation.

Main Results:

• DMAB crystals exhibited continuous crawling motion on functionalized gold surfaces when exposed to UV and visible light.
• Surface wettability significantly influenced crawling velocity and crystal shape; hydroxyl-terminated surfaces yielded higher velocities and maintained crystal facets, while alkyl-terminated surfaces resulted in droplet-like shapes and slower motion.
• Crystal motion was primarily dictated by surface wettability, with patterned substrates showing locomotion preference for specific surface chemistries and the ability to traverse topographical steps.

Conclusions:

• Surface wettability is a more dominant factor than surface structure in controlling photo-induced crawling motion of DMAB crystals.
• The findings offer a pathway for controlling micro-crystal movement on surfaces.
• This research paves the way for novel applications in molecular/object transport vehicles at the microscale.