| Aug 20, 2025 |
3D printing method mimics tissue behavior for advanced biomedical implants
Scientists developed a 3D printing method that creates hydrogels with tissue-like properties, paving the way for personalized implants and adaptive soft robotics.
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(Nanowerk News) Human tissues like skin, arteries, and cartilage share a remarkable property. When stretched, they stiffen dramatically after reaching a certain limit, protecting them from tearing or overextension. This behavior, known as strain-stiffening, helps tissues perform essential functions under physical stress. In skin, for example, collagen fibers reorient under tension so the tissue does not overstretch. Scientists describe this natural ability as hierarchical mechanoresponsiveness.
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Synthetic materials such as hydrogels, which are widely used in bioimplants, have struggled to mimic this property. While hydrogels can be soft and biocompatible, they usually lack the dynamic responsiveness and structural complexity of living tissues.
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A research team led by Professor Zhilu Yang of Southern Medical University and Professor Xuetao Shi of South China University of Technology has been working to bridge this gap. They previously engineered a polyvinyl alcohol (PVA)-based hydrogel that showed tissue-like strain-stiffening and formed intricate microstructures. But the challenge remained: existing fabrication methods could only produce flat sheets or films, limiting the material’s use in more complex biomedical devices. Traditional approaches also could not support 3D printing of these hydrogels into intricate shapes.
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To overcome this, the researchers developed a new method called immersion phase separation 3D printing (IPS 3DP). Their study, published in Research ("Immersion Phase Separation 3-Dimensional Printing for Strain-Stiffening Hydrogel Scaffolds"), details how the technique works. Instead of simply extruding hydrogel ink, IPS 3DP relies on controlling the rate at which solvent molecules in the ink diffuse into a liquid bath. By carefully tuning the bath composition and the solvent exchange process, the team was able to print complex, robust structures that still retained the strain-stiffening seen in natural tissues.
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| Overview of immersion phase separation 3-dimensional printing (IPS 3DP). (A) Schematic diagram of IPS 3DP, where polymer refers to PVA-C5-DS; solvent refers to dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), etc.; and nonsolvent refers to water. (B) Synthetic equation of PVA-C5-30, photographs of the PVA-C5-30 samples, and IPS 3DP ink. (C) Representative photographs of the IPS 3DP process. (D) Ternary diagrams for the PVA-C5-30/DMSO/water ternary systems. (E) IPS 3DP scaffolds modified by hydroxyapatite (HA), carbon nanotubes (CNTs), and nano-copper powder doping were used, named HA-IPS scaffold, CNT-IPS scaffold, and Cu-IPS scaffold, respectively. PVA, polyvinyl alcohol; CDI, N,N′-carbonyldiimidazole. (Image: reprinted from DOI:10.34133/research.0742, CC BY) (click on image to enlarge)
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Through systematic experiments, the team determined the optimal ink formulations—especially the right concentration of dimethyl sulfoxide (DMSO), a key solvent—that allow the material to solidify at the right pace after extrusion. The printed hydrogels showed impressive mechanical properties, including high fracture strength and the ability to stretch more than ten times their original length. They also developed controlled pore sizes and microchannels that mimic tissue organization.
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Importantly, the new process also reduces waste. When printing errors occur, the material can be recovered and reused with more than 95 percent efficiency. Beyond their mechanical strength, the printed hydrogels can be customized with added fillers such as hydroxyapatite for bone regeneration, carbon nanotubes for electrical conductivity, or copper particles for antimicrobial properties.
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The researchers believe this approach could open the door to personalized implants and new types of soft robotics that respond to their environment more like living tissue. “These advancements establish IPS 3DP as a transformative platform for personalized biomedical implants and adaptive soft robotics,” said Professor Yang.
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By merging the precision of 3D printing with the adaptive behavior of natural tissues, IPS 3DP offers a pathway toward biomimetic devices that can be tailored for individual patients.
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