Droplet backside exposure for making slanted SU-8 microneedles

Area of Science:

• Materials Science
• Microfabrication
• Polymer Science

Background:

• Microneedle arrays are crucial for transdermal drug delivery and biosensing.
• Existing fabrication methods often lack control over microneedle angle and dimensions.
• Flexible polymer substrates are desirable for wearable and implantable devices.

Purpose of the Study:

• To introduce and validate a new droplet backside exposure (DBE) method for fabricating slanted microneedles.
• To demonstrate precise control over microneedle length and structure using the DBE technique.
• To investigate the underlying principles governing microneedle formation in the DBE process.

Main Methods:

• Fabrication of SU-8 microneedle arrays on polydimethylsiloxane (PDMS) substrates using the DBE method.
• Utilizing the wetting barrier phenomenon at a liquid-vapor-hydrophilic surface-hydrophobic surface interface to control microneedle dimensions.
• Employing analytical modeling to predict and correlate with experimental microneedle dimensions.

Main Results:

• Successful fabrication of slanted microneedle structures on flexible PDMS substrates.
• Demonstrated excellent repeatability and controllability in microneedle length via droplet volume adjustment.
• Analytical models accurately predicted microneedle dimensions, showing good agreement with experimental data.

Conclusions:

• The droplet backside exposure (DBE) method is a feasible and effective technique for producing slanted microneedles.
• The DBE approach offers precise control over microneedle geometry, essential for advanced applications.
• This method holds promise for scalable and cost-effective manufacturing of microneedle arrays.