Design and Fabrication of a Spin Coater with In-Situ Optical Measurement for Soft Thin Films

2026-06-12

AI Summary

This study addresses the challenge of achieving non-destructive, high-precision, and low-cost thickness control of soft polymeric films during spin coating—a critical limitation for devices such as dielectric elastomer actuators. The authors present a low-cost, desktop-scale spin-coating platform based on 3D printing, integrated for the first time with a low-deformation, laser-reflection-based in situ thickness measurement system. By employing a quadrant photodetector to track real-time displacement of the reflected laser beam, the system enables controlled fabrication of soft films with thicknesses ranging from 50 to 300 µm. Optimized via finite element analysis and calibrated using metal shims, the setup achieves a thickness resolution of 3.6–3.7 µm and a repeatability error of 13 µm (95% confidence interval), successfully producing silicone films with deviations from target thickness of less than 9 µm.

Abstract

Spin coating is widely used for fabrication of thin polymer and elastomer films, yet reliable thickness verification of highly compliant materials remains challenging due to deformation from contact-based measurements and the cost and complexity of conventional optical metrology. Accurate thickness control is especially critical in soft elastomer applications such as dielectric elastomer actuators (DEAs), where mechanical and functional performance scales strongly with film thickness. This work presents a low-cost, primarily 3D-printed benchtop spin coater with an integrated, minimally deforming optical thickness measurement system for soft-film fabrication workflows. The system is designed to manufacture films between 50 and 300 microns thick with repeatability within 10 microns. Thickness is measured in-situ by tracking displacement of a reflected laser beam via quadrant photodetector, avoiding significant deformation. Optical geometry, sensor linearity constraints, and structural validation via finite element analysis are discussed. Experimental validation using calibrated metal shims demonstrated a thickness resolution of 3.6-3.7 microns and best-case measurement repeatability of 13 microns (95 percent confidence interval). The platform repeatably produced silicone films within 9 microns of target thickness, demonstrating that accessible optical metrology can be integrated into a low-cost spin coating system for practical, thickness-controlled fabrication of compliant thin films without specialized industrial instrumentation.

Problem

• spin coating
• soft thin films
• thickness measurement
• optical metrology
• dielectric elastomer actuators

Innovation

• in-situ optical measurement
• spin coater
• soft thin films
• non-contact thickness metrology
• 3D-printed instrumentation