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Nature Sub-Journal: Hybrid Resin with 3,000-Fold Strength Difference Enables Dual-Wavelength 3D Printing

2026-01-07

While we are still troubled by the single performance of traditional 3D printing materials, a research team at the University of Texas at Austin has developed a groundbreaking technology in their laboratory.

Their latest research findings, published in the journal Nature Materials, have caught the attention of AM Easy Way: a hybrid epoxy-acrylate resin system that enables an unprecedented combination of strength, elasticity, and aging resistance through wavelength-selective multi-material 3D printing technology.

Technological Leap from Bionics to Reality

As it turns out, nature has long given us the answer.

Structures in nature combine rigid and flexible materials in precise three-dimensional arrangements, endowing them with overall performance and functions that are difficult to replicate by synthetic technologies.

Think about our knee joints—hard bones and flexible ligaments work perfectly together, allowing us to walk and run freely.

Inspired by this bionic concept, the research team at the University of Texas set out to replicate this magical combination in the field of 3D printing.

The core breakthrough of the research team lies in the development of a hybrid epoxy-acrylate monomer system. They selected (3,4-epoxycyclohexyl) methyl acrylate (ECA) as a hybrid acrylate-epoxy monomer for wavelength-selective free-radical and cationic photocuring.

Sounds complicated? Simply put, it is a material that can exhibit completely different properties under different light conditions.

As shown in Figure 1, this innovative method stands in stark contrast to traditional technologies. The limitations of traditional grayscale printing and multi-color printing methods have been effectively overcome. The new hybrid resin method achieves high printing speed, low sol fraction, and a stiffness difference of more than 1,000 times.

The Ingenious Coordination of Dual Wavelengths

The essence of this system lies in wavelength-selective photopolymerization.

The team optimized the photoinitiator system for 365 nm and 405 nm LED emissions, where 365 nm light is used for epoxy curing and 405 nm light for acrylate curing.

Different light wavelengths can activate different chemical reactions, thereby creating material regions with vastly different properties in a single printing process.

Extended Reading: Ingenious Dual-Wavelength Synchronous Curing! A Single Solution to the Problem of Manual Support Removal in 3D Printing

Real-time Fourier transform infrared spectroscopy analysis shows that under 365 nm or 405 nm LED irradiation, rapid polymerization reaches 50% conversion rate in approximately 2 seconds.

This reaction rate ensures the practicality of 3D printing, without slowing down production efficiency due to complex chemical processes.

The differentiated performance of the material is even more impressive.

UV-cured samples form rigid and tough plastics with an elastic modulus of 1700±140 MPa, a maximum strength of 69±6 MPa, and an elongation at break of 8±2%.

In contrast, violet-light printed samples exhibit soft and stretchable characteristics with an elastic modulus of only 0.60±0.09 MPa, a maximum strength of 0.78±0.05 MPa, but an elongation at break as high as 260±40%.

Figure 2 details the resin components and wavelength-selective curing mechanism, clearly illustrating the process of polymerization reactions of various chemical components under different wavelengths of light.

Performance: Beyond Expectations in Material Combination

Let us speak with data. This system achieves a stiffness difference of approximately 3,000 times. The rigid material has a strength of over 50 MPa, the flexible material can withstand more than 100% strain, and the elastic recovery rate is ≥90%.

Cyclic tensile tests show that the violet-light printed samples exhibit an elastic recovery rate of >99% and a hysteresis loss of only about 3-4% after 100 cycles of loading under 100% strain.

What does this performance mean in practical applications?

You can simultaneously manufacture rigid skeleton structures and flexible connecting components in one printing process, and the interfaces between these components can withstand repeated mechanical stress without failure.

Figure 3 clearly shows the multi-color DLP 3D printing system and thermomechanical property characterization, including a schematic diagram of the printing system and stress-strain curves of rigid and flexible materials, intuitively reflecting the performance differences between the two materials.

Resolution and Precision

In terms of resolution, this system also performs excellently.

Optical microscope observations show that alternating UV and violet light exposure lines can achieve clear features with a minimum of 0.25 mm.

More importantly, nanoindentation tests show that at the rigid-flexible interface, the contact modulus increases by three orders of magnitude over a distance of approximately 200 microns.

This precise control capability allows researchers to create bionic mechanical gradients.

By superimposing grayscale UV and violet light projections, the team programmed three different mechanical gradients in 3D printed bars, simulating the stiffness changes of knee joints, tooth enamel, and squid beaks, spanning a reduced modulus range of about three orders of magnitude.

Figure 4 fully demonstrates the resolution and mechanical characterization of 3D printed multi-material objects, including printed structures with different line widths and nanoindentation test results, proving the system's precise control capability at the micro level.

Bionic Applications: From Spine to Knee Joint

The bionic structural applications demonstrated by the research team are breathtaking.

They fabricated structures with rigid springs embedded in flexible cylinders, simulating the compression damping characteristics of the spine.

Compression test results show that as the spring pitch decreases from 4 mm to 2 mm, the stiffness increases by about four times, and the compressive strains under 50N load are 28%, 18%, and 8%, respectively.

This scaled-down human knee joint is approximately 46.5 mm in height, 17.5 mm in width at the knee, and the smallest feature (ligament/tendon) has a diameter of approximately 0.6 mm.

The rigid femur, patella, and tibia are cured using UV light, while the soft and stretchable tendons and ligaments are printed synchronously using violet light.

Figure 5 vividly shows the 3D printing applications of bionic mechanical metamaterials, including the design and test results of compression damping structures and gradient joint structures, fully demonstrating the great potential of this technology in the field of bionic manufacturing.

New Possibilities for Stretchable Electronics

In terms of stretchable electronics applications, this system shows enormous potential.

The research team evaluated the strain distribution of stiffness inserts with different stiffness under tensile deformation through finite element analysis (FEA) and digital image correlation technology.

FEA simulations show that under 30% global uniaxial strain, increasing the insert stiffness can reduce the local strain to approximately 4% (10 times), approximately 0.5% (100 times), and approximately 0.05% (1000 times).

The final proof-of-concept is quite fascinating. The research team deposited gold on the central inserts of 1x and 1000x samples and connected white LEDs. When stretched to 30% global strain, the 1x sample fractured, causing the circuit to disconnect and the LED to turn off, while the 1000x sample remained intact.

Figure 6 details the local deformation control in multi-material tensile specimens, including FEA simulation results and tests of stretchable LED device prototypes, providing strong technical support for stretchable electronics applications.

Final Thoughts

A key limitation of the current process is the need for extensive solvent cleaning to ensure long-term material stability, which is particularly relevant for designs where soft materials are fully encapsulated within rigid structures.

AM Easy Way believes that this research provides new ideas for multi-material manufacturing in 3D printing. In application fields such as soft robotics, seals, prosthetics, and wearable health monitoring devices, this technology that can achieve extreme performance differences in a single print will bring significant advantages.

Future extended functional features are not limited to mechanical properties, including thermal, electrical, and optical tunability, which will further expand the application boundaries of this technology.

In the end, when a 3D printer can simultaneously produce parts as hard as steel and as soft as rubber in one operation, those product designs that originally required complex assembly will be replaced and digitally upgraded by 3D printing once again.

#3DPrinting #MultiMaterialPrinting #BionicManufacturing #DLP #HybridResin #WavelengthSelectivePolymerization #StretchableElectronics #SoftRobotics

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