Polymer Pen Lithography with Lipids for Large-Area Gradient Patterns.

Area of Science:

• Biomedical Engineering
• Materials Science
• Surface Chemistry

Background:

• Gradient patterns of bioactive compounds are crucial for biomedical applications like cell screening and migration studies.
• Polymer pen lithography (PPL) offers a highly parallel, large-area patterning technique with potential for fabricating such gradients.

Purpose of the Study:

• To present strategies for fabricating functional phospholipid patterns using PPL with tunable feature size and density gradients.
• To explore different transfer modes within PPL for controlling feature morphology and creating membrane-like structures.

Main Methods:

• Utilized polymer pen lithography (PPL) to print phospholipid patterns on millimeter-square areas.
• Controlled printing parameters, including applied force, to switch between dip-pen nanolithography (DPN) and microcontact printing (μCP) transfer modes.
• Optimized inking procedures and substrate properties (smooth, hydrophilic) to achieve membrane-spreading dominated transfer and constant feature height.

Main Results:

• Achieved tunable feature size and density gradients over large surface areas (several mm²).
• Demonstrated two distinct transfer modes (DPN-like and μCP-like) with different feature morphologies by adjusting printing force.
• Generated gradient patterns with features of consistent height, comparable to biological cell membranes, without substrate pre-functionalization.
• Confirmed the viability of the phospholipid patterns for subsequent protein binding.

Conclusions:

• PPL provides a versatile platform for creating functional phospholipid gradients for biomedical applications.
• The ability to control transfer modes and feature morphology allows for precise construction of membrane-like structures.
• These gradient patterns offer a flexible foundation for applications requiring controlled presentation of bioactive molecules, such as protein gradients.