Micro 3D Printing of a Temperature-Responsive Hydrogel Using Projection Micro-Stereolithography

Daehoon Han,Howon Lee,Zhaocheng Lu,Shawn A Chester

doi:10.1038/s41598-018-20385-2

Abstract

Stimuli-responsive hydrogels exhibiting physical or chemical changes in response to environmental conditions have attracted growing attention for the past few decades. Poly(N-isopropylacrylamide) (PNIPAAm), a temperature responsive hydrogel, has been extensively studied in various fields of science and engineering. However, manufacturing of PNIPAAm has been heavily relying on conventional methods such as molding and lithography techniques that are inherently limited to a two-dimensional (2D) space. Here we report the three-dimensional (3D) printing of PNIPAAm using a high-resolution digital additive manufacturing technique, projection micro-stereolithography (PμSL). Control of the temperature dependent deformation of 3D printed PNIPAAm is achieved by controlling manufacturing process parameters as well as polymer resin composition. Also demonstrated is a sequential deformation of a 3D printed PNIPAAm structure by selective incorporation of ionic monomer that shifts the swelling transition temperature of PNIPAAm. This fast, high resolution, and scalable 3D printing method for stimuli-responsive hydrogels may enable many new applications in diverse areas, including flexible sensors and actuators, bio-medical devices, and tissue engineering.

Highlights

(PNIPAAm), a temperature responsive hydrogel, has been extensively studied in various fields of science and engineering
In order to build a 3D object in a layer-by-layer fashion, we studied how a layer of PNIPAAm hydrogel is polymerized and grows in the vertical direction
We presented the 3D fabrication of PNIPAAm micro-structures using high resolution PμSL

Summary

Introduction

(PNIPAAm), a temperature responsive hydrogel, has been extensively studied in various fields of science and engineering. When the temperature increases above the LCST, hydrophobic groups become more active, causing the molecules to transform into a shape resembling a compact globule. Such a dramatic change induces the escape of entrapped water molecules from the hydrogel network, resulting in a significant reduction of volume. Despite the growing attention to PNIPAAm and its wide range of applications, manufacturing techniques for PNIPAAm have been limited to simple two-dimensional (2D) fabrication methods such as molding and lithography, which impedes full utilization of its unique material behavior. Other high resolution 3D micro-manufacturing techniques including three-dimensional laser chemical vapor deposition (3D-LCVD)[20], electrochemical fabrication (EFAB)[21], and micro-stereolithography (μSL)[22] have drawbacks such as long fabrication time, high cost, and limited sets of available materials

Methods

Results

Conclusion