Producer: Popular Science China
Author: Shi Chang (Ph.D. in Physical Chemistry)
Producer: China Science Expo
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Today, with the rapid development of science and technology, 3D printing technology is like a strong east wind, blowing all walks of life. From complex and precise mechanical parts to lifelike models, from fantastic architectural prototypes to personalized daily necessities, 3D printing technology brings people's imagination into reality with its infinite creativity and flexibility, bringing convenience and surprise to our lives.
3D printing of production models
(Image source: Veer Gallery)
Do you know about 3D printing technology?
3D printing, also known as additive manufacturing, is an innovative production method that builds three-dimensional solids by stacking materials layer by layer. The principle of 3D printing technology is similar to that of building a house with bricks, which can be simply summarized as "layered manufacturing, layer by layer".
The entire process of 3D printing is not complicated, starting with the creation or acquisition of a digital model through computer-aided design software, and then cutting the model into a series of very thin cross-sectional layers (i.e., slices), each layer is typically between tens and hundreds of microns thick. Then, based on this slice information, the 3D printer uses specific techniques and materials to build the final object layer by layer.
The processes of 3D printing include fused deposition modeling (FDM), light-curing 3D printing (SLA, DLP, LCD), selective laser sintering (SLS), selective laser melting (SLM), stereoscopic inkjet printing (3DP), and laminated solid manufacturing (LOM).
A working 3D printer
(Image source: Veer Gallery)
Fused deposition modeling technology is to heat and melt filamentous thermoplastic materials through a nozzle, deposit them layer by layer on a platform, and finally solidify into a three-dimensional object. The raw materials commonly used in this technology are thermoplastic materials, such as ABS (acrylonitrile-butadiene-styrene copolymer), PLA (polylactic acid), etc. The technology is less demanding and easy to operate, making it suitable for use by individuals and small studios. The "carrot knife" and "telescopic sword", which have recently become popular in the toy market, are made in this way.
The principle of light-curing 3D printing is to use light in a specific wavelength band and shape to irradiate the photosensitive resin, and through the layer-by-layer curing of the photosensitive resin, the desired shape of the object is generated. This technology has high molding accuracy and smooth surface, which is suitable for making fine models and small parts.
Selective laser sintering uses a laser beam to scan a powdered material, melt it and bond it together, accumulating layer by layer into a three-dimensional object. This technology uses powder as raw material (such as nylon, metal powder, ceramic powder, etc.), with high molding accuracy, and is suitable for manufacturing complex structural and functional parts.
Selective laser melting is similar to selective laser sintering, but with higher laser energy and the ability to completely melt metal powders for rapid prototyping of metal parts. This technology often uses metal powder (such as titanium alloy, stainless steel, etc.) as raw materials, which can print high-strength and high-precision metal parts, and is widely used in aerospace, medical and other fields.
Stereo inkjet printing is a process of printing parts layer by layer using powdered materials (metal or non-metal) and adhesives as raw materials. The sample formed by this printing technology has the same color as the actual product, which is a relatively mature color 3D printing technology.
Laminated solid manufacturing uses thin sheet materials (such as paper, plastic film, etc.) and hot melt adhesive as raw materials, which are accumulated layer by layer through laser cutting and thermal bonding to form the desired object. This technology has a fast molding speed and low material cost, which is suitable for making large structures and enclosures.
Although the 3D printing technology has been relatively mature and the reduction degree of the product is high, due to the limitation of printing raw materials, 3D printing products have high brittleness and are prone to fracture by external forces. This type of product is a bit "inadequate" when applied in scenarios with high mechanical performance requirements. So, how to improve the glass core of 3D printing products with "good-looking skin" and flexibility at the same time?
On July 3, 2024, Chinese scientists published a research result on 3D printed elastomers in the journal Nature, in which the rubber bands prepared by this technology can be stretched to 9 times their own length, with a maximum tensile strength of 94.6 MPa, which is equivalent to 1 square millimeter can withstand a gravity of nearly 10 kg, showing ultra-high strength and toughness.
研究成果发表于《Nature》杂志
(Image source: Nature magazine)
What makes this rubber band so special?
In the process of light-curing 3D printing, in order to improve production efficiency, a fast molding speed is often required, which leads to the increase of cross-linking density and the decrease of material toughness during the curing process. Conventional methods of increasing the toughness of a material will increase the viscosity of the material, reduce the flowability, and lead to a decrease in the molding speed. The contradictory relationship between the molding speed of 3D printing and the toughness of the finished product has long plagued the entire industry.
But these two contradictions have been "reconciled" in the hands of Chinese scientists. Through the analysis of photosensitive resin, a raw material for light-curing 3D printing, and the dismantling of the printing process, the researchers proposed a strategy for printing and post-processing in stages. The researchers designed a DLP (digital photoprocessing) precursor of dimethacrylate that contains a dynamically hindered urea bond and two carboxyl groups on the backbone. During the printing stage, these key components are in a "dormant" state and play a toughening role in the post-molding processing stage.
a.3D the printed object and its dimensional change during post-processing, the puncture resistance of the b.3D printed balloon, c. the modeling of the mechanical puncture force, and the d-e.3D printing of the pneumatic fixture lifting test
(Image source: Reference 1)
At 90°C, the hindered urea bonds in the 3D printed product are dissociated to form an isocyanate group, which reacts with the side-chain carboxyl group to form amide bonds on the one hand, and with the water adsorbed by carboxylic acids on the other hand. The chemical bond changes that occur within the molecule connect the single network structure in the material into an interpenetrating network structure similar to "hand-in-hand", and bring more hydrogen bonds, so that the internal structure of the material is strengthened. It is precisely because of the change of the internal structure of the material that the 3D printed finished product has a larger buffer space when deformed by external forces, which is similar to the energy absorption effect of vehicle collision, which improves the impact and fracture resistance of the product and has higher toughness.
The experimental results show that the film with a thickness of only 0.8 mm prepared by 3D printing using DLP precursor shows strong anti-acupuncture performance and can not break under the force of 74.4 N. Even under high-pressure inflation, the 3D-printed pneumatic gripper is still able to grip copper balls weighing up to 70 grams with sharp spines on the surface without breaking. It demonstrates the ultra-high toughness and structural strength of 3D printed products.
What are the applications of 3D printed elastomers?
In the field of sports equipment, 3D printed elastomers provide athletes with more personalized and high-performance equipment. For example, customized insoles and protective gear take advantage of the shock-absorbing and supportive properties of elastomers to optimize athletes' athletic performance and enhance the wearing experience. Especially in extreme sports and high-impact sports, 3D printed elastomer materials can significantly reduce the impact athletes receive during sports, protecting their joints and muscles from damage.
3D printed insoles
(Image source: Veer Gallery)
In the automotive and aerospace sectors, 3D printed elastomers are used in key components such as lightweight shock-absorbing components and seals. These components are designed with a complex structure that reduces weight and maintains high performance.
Auto parts
(Image source: Veer Gallery)
In the field of electronic products, smart speakers, smart bracelets, mobile phone cases and other products can be printed with elastomer materials. These products not only have excellent softness and elasticity, but also have high wear resistance and durability, which can meet the multifaceted needs of consumers for product appearance and performance.
Smart bracelets
(Image source: Veer Gallery)
In the field of industrial manufacturing, 3D printing elastomer technology is used to manufacture components such as various industrial molds and transmission belts. These components need to withstand high mechanical stresses and vibrations, and elastomer materials are ideal for their excellent elasticity and fatigue resistance. The manufacture of these parts through 3D printing technology not only improves production efficiency, but also reduces manufacturing costs.
conveyor belt
(Image source: Veer Gallery)
epilogue
3D printing technology occupies an increasingly important position in our lives, and the advent of 3D printing elastomer technology has further enriched the use scenarios of 3D printing products. The progress of science and technology has given infinite possibilities to life, and we also look forward to more technological development and technological innovation to make our lives more colorful.
Bibliography:
1.Fang, Z., Mu, H., Sun, Z. et al. 3D printable elastomers with exceptional strength and toughness[J]. Nature,2024.
2.Walker, D. A., Hedrick, J. L. & Mirkin, C. A. Rapid, large-volume, thermally controlled 3D printing using a mobile liquid interface[J]. Science,2019.
3. Zhang Xuejun, Tang Siyi, Zhao Hengyue, et al. Research status and key technologies of . 3D printing technology[J].Materials Engineering, 2016.
4. Huang Jian, Jiang Shan.3D will printing technology set off the "third industrial revolution"? New Materials Industry, 2013.