Stimuli-responsive wettability of nonplanar substrates: pH-controlled floatation and supporting force

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Developing smart materials with tunable surface properties is crucial for advanced applications.
• pH-responsive materials offer dynamic control over surface characteristics based on environmental acidity.
• Gold surfaces are widely used in sensors and microdevices, but their surface properties often require modification.

Purpose of the Study:

• To engineer pH-responsive planar and nonplanar gold substrates.
• To investigate the relationship between pH, surface wettability, and mechanical support.
• To explore the potential of these modified surfaces for controlling the motion of gold threads.

Main Methods:

• Chemical modification of a rough gold surface using 2-(11-mercaptoundecanamido)benzoic acid (MUABA).
• Measurement of contact angle (CA) as a function of pH to assess surface wettability.
• Evaluation of the supporting force of MUABA-coated gold threads at different pH levels.

Main Results:

• The modified rough gold surface exhibited a large pH-responsive change in contact angle, transitioning from superhydrophobic (144°) to superhydrophilic (0°).
• MUABA-coated gold threads demonstrated greater supporting forces at low pH compared to high pH due to hydrophobicity.
• Changes in surface wettability influenced the flotation behavior of gold threads, suggesting a method for motion control.

Conclusions:

• Chemically modified gold surfaces with MUABA display significant pH-responsive wettability.
• The pH-dependent mechanical properties and wettability of MUABA-coated gold threads can be leveraged for controlled motion.
• This study presents a novel approach for manipulating the behavior of gold microstructures in aqueous environments.