Micro/nanofabrication of brittle hydrogels using 3D printed soft ultrafine fiber molds for damage-free demolding

Abstract

Hydrogels are very popular in biomedical areas for their extraordinary biocompatibility. However, most bio-hydrogels are too brittle to perform micro/nanofabrication. An effective method is cast molding; yet during this process, many defects occur as the excessive demolding stress damages the brittle hydrogels. Here, we propose a brand-new damage-free demolding method and a soft ultrafine fiber mold (SUFM) to replace the traditional mold. Both mechanical and finite element analysis (FEA) reveal that SUFMs have obvious advantages especially when the contact area between hydrogel and mold gets larger. By means of a high-resolution 3D printing called electrohydrodynamic (EHD) printing, SUFMs with various topological structures can be achieved with the fiber diameter ranging from 500 nm to 100 μm, at a low cost. Microfluidics and cell patterns are implemented as the demonstration for potential applications. Owing to the tiny scale of microstructures and the hydrophilicity of hydrogels, significant capillary effect occurs which can be utilized to deliver liquid and cells autonomously and to seed cells into those ultrafine channels evenly. The results open up a new avenue for a wider use of hydrogels in biomedical devices, tissue engineering, hydrogel-based microfluidics and wearable electronics; the proposed fabrication method also has the potential to become a universal technique for micro/nanofabrication of brittle materials.

A Perspective on Using Machine Learning in 3D Bioprinting

“…Figure 1a shows a typical extrusion-based 3D printing process to manufacture a component. 3D bioprinting is a process that uses 3D printing-like technologies to fabricate biomedical parts that consist of biomaterials, growth factors and cells, with the aim of maximally imitating natural tissue characteristics[ 9 - 11 ]. The fabrication process of 3D bioprinting is similar to 3D printing that uses a layer-by-layer method to deposit materials[ 12 - 14 ].…”

Hydrogels: The Next Generation Body Materials for Microfluidic Chips?

“…[65] However, during demolding, many defects emerge as excessive demolding stress damages brittle hydrogels. To solve this problem, our group has proposed a damage-free demolding method based on a soft intricate fiber mold to replace the traditional rigid mold, which has been applied for the creation of micro/nano-structures on the surface of GelMA hydrogel, [167] as shown in Figure 3B. By applying high-resolution near-field 3D printing, soft fiber templates exhibiting various topological patterns with the fiber diameter ranging from 500 to 100 µm could be obtained at a low cost.…”

“…Targeting the challenges caused by the properties of hydrogels, a universal process flow for the construction of HMCs is proposed. [156,167,196] As displayed in Figure 5, through the combination of 3D printing technology, damage-free demolding method, and twice-crosslinking bonding strategy, the whole process includes: 1) model design of the microfluidic channel, 2) 3D printing of the fiber template, 3) hydrogel casting (uncrosslinked hydrogel), 4) template demolding (creation of micro-structures on partially crosslinked hydrogel) 5) hydrogel bonding (formation of a encapsulated channel in completely crosslinked hydrogel), 6) cells loading (specific cells located on specific position).…”

“…Reproduced with permission. [ 167 ] Copyright 2020, IOP Publishing. B‐ii) Illustration of the damage‐free demolding process.…”

“…Reproduced with permission. [ 167 ] Copyright 2020, IOP Publishing. C‐i) Schematic overview of the monolithic tissue construct containing patterned vascular architectures and living cells.…”