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Rutgers Engineers 4D Printing Smart MetaMaterials for Industrial Applications

Engineers at Rutgers University–New Brunswick are advancing beyond the realm of 3D printing, now fabricating smart materials in 4D that will transform as needed, according to their environment. Such structures could become transforming for numerous high-level applications, with shock-absorbing materials that will change as needed, for use in examples such as: aircraft or drone design for parts like wings that need to self-alter for varying performance, soft robotics meant to perform a wide range of tasks, and tiny, minimally invasive medical implants.

Findings regarding this latest research are outlined in ‘4D Printing Reconfigurable, Deployable and Mechanically Tunable Metamaterials.’ As the researchers explain, most metamaterials, as exotic and mechanically-tuned as they may be, are composed of fixed properties and are not able to adapt to many of the specific needs that users have today. With so much progressive technology at our fingertips, it really doesn’t seem to be too much to ask for materials to bend to our will. The Rutgers scientists don’t disappoint here either, creating complex geometries that are:

  • Geometrically reconfigurable
  • Functionally deployable
  • Mechanically tunable
  • Unique and lightweight

“Using digital micro 3D printing with a shape memory polymer, dramatic and reversible changes in stiffness, geometry, and functions of metamaterials are achieved,” state the researchers in their paper, authored by Howan Lee, Chen Yang, Manish Boorugu, Andrew Dopp, Jie Ren, Raymond Martin and Daehoon Han, all current or former Rutgers students, and Professor Wonjoon Choi at the Korea University.

Typical triggers in 4D printed materials are changes in temperature, exposure to moisture, and the amount of time elapsed. Materials, often made with different polymer-like substances, will remain rigid if pushed down—or they can become pliable and absorbent, functioning to absorb impact and shock. The scientists working on the project say that such materials can be transformed and deformed—and then they will revert upon exposure to heat.

4D-printed metamaterials can be temporarily transformed into any deformed shape and then returned to their original shape on demand when heated. The scale bar is 2 millimeters.
(Photo credit: Chen Yang/Rutgers University-New Brunswick)

“The stiffness can be adjusted more than 100-fold in temperatures between room temperature (73 degrees) and 194 degrees Fahrenheit, allowing great control of shock absorption,” states the research team.

“We believe this unprecedented interplay of materials science, mechanics and 3D printing will create a new pathway to a wide range of exciting applications that will improve technology, health, safety and quality of life,” says senior author Howon Lee, assistant professor in the Department of Mechanical and Aerospace Engineering.

Still-shot from video accompanying Rutgers press release.

While 3D printing is still taking the world by storm, from the DIY crowd to the upper echelons of industrial manufacturing from GE to NASA, technology has already evolved to the next level with 4D printing. Just as 3D printing offers the potential for incredible customization, like medical innovations that will allow for patient-specific care, 4D printing allows for materials to morph into desired shapes and textures for creations such as load-bearing structures, seating in luxury vehicles, and so much more—to include many forays into fashion like clothing and wearables.

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[Source / Images: Rutgers news release]

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Beijing: Researchers 3D Print Chiral MetaMaterials

If you have been heavily influenced by 3D printing or are just a fan of the many innovations brought forth today, chances are you have also become far more knowledgeable about materials science than you ever imagined. While in the beginning 3D printing was greatly ruled by thermoplastics such as ABS and PLA, the list of materials today is expansive—with some being wildly alternative from chocolate to hemp—and the choices just continue to grow.

Metamaterials allow researchers to create on an even more elevated level, and continued strides may change the face of how numerous applications are manufactured in the future. Recent work by Beijing researchers, discussed in ‘Deformation mechanism of innovative 3D chiral metamaterials,’ explores the importance of man-made materials that can be microstructured to include properties not available naturally. They also examine deformation mechanisms, to include:

  • Uniform spatial rotation deformation
  • Tensile-shearing directed
  • Tensile-expansion directed
  • Deformation mechanisms of 3D chiral metamaterials
  • Deformation mechanism competition between varying types

(a–d) x-y, y-z, z-x and stereo views of as-fabricated chiral- chiral- antichiral metamaterials; (e–h) x-y, y-z, z-x and perspective view of as-fabricated chiral- antichiral- antichiral metamaterials.

The chiral metamaterials explored by the team of researchers offers strong potential for designing with a variety of strengths and densities, sound metamaterials, electromagnetic metamaterials, optical metamaterials, and more. The research paper goes into detail regarding the expanding qualities of auxetic metamaterials, along with their ‘enhanced’ mechanical properties.

“Auxetic materials can be applied for designing innovative multifunctional structures, such as: body armor, packing material, knee and elbow pads, robust shock absorbing material and sponge mops. According to the geometrical relations of auxetic unit cell, there are mainly three types of auxetic materials: reentrant materials, rigid square rotation materials and chiral structures,” state the researchers.

A chiral structure is one that cannot be separated into two identical halves. A good example is that of a DNA strand. The researchers point out that other natural chiral materials are that of flower petals and stems that climb in a twisted fashion, as well as ‘tendrils and twisted leaves.’

“Because of their lack of mirror symmetry, chiral metamaterials have recently enabled several remarkable phenomena, such as negative refractive index, superchiral light, and use as broadband circular polarizers or detectors,” state the researchers.

The x-y, y-z, z-x and stereo views of the architected 3D chiral matamaterials (a,b,c) and (d) chiral- chiral- antichiral metamaterials; (e,f,g) and (h) chiral- antichiral- antichiral metamaterials.

With 3D printing, chiral structures can be fabricated with even greater functionality in applications such as electronics. In the scope of this research study, the team focused on chiral- chiral- antichiral, and chiral- antichiral- antichiral metamaterials. Type A and Type B were 3D printed on an SLS 3D printer at BMF Material Technology, Inc. in Guang Dong Province of China.

The nylon was evaluated before compression tests began:

“Totally, 5 uniaxial tensile samples are fabricated, and uniaxial tensile experiments are performed on an Instron®5985 machine at a displacement rate of 1 mm/min. Finally, the average elastic modulus of the 5 as-fabricated tensile samples is:Es = 1021.00 MPa, where the deviation of modulus is: ±0.75 MPa, and the average ultimate strain of the material is εmax = 0.16,” stated the researchers.

The researchers then employed compression tests, noting:

  • Loading force
  • Displacement images
  • Deformation images

Axial strain and compression stress were created as the researchers worked to minimize friction. Beyond that, they continued to simulate deformation and then compare all the results.

“With the progress of micro- and nano- manufacturing techniques, the proposed 3D chiral metamaterials show promising performances for future industrial applications, such as: nano chiral metallic glass with extensive hardening and large ductility, sound absorption and vibration attenuation metamaterials, morphing structures, optical chiral metamaterials, shape memory actuators and biomechanical devices,” concluded the researchers.

What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

[Source / Images: Deformation mechanism of innovative 3D chiral metamaterials]

 

The x-y, y-z, z-x and stereo views of the architected 3D chiral matamaterials (a), (b), (c) and (d) chiral- chiral- antichiral metamaterials; (e), (f), (g) and (h) chiral- antichiral- antichiral metamaterials.

 

 

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Researchers Demonstrate Wideband Metamaterial Absorber Made of 3D Printed Conductive Plastic

Architecture of the wideband MA

There’s been a lot of research into 3D printing metamaterials over the years – due to their unique properties, they’ve been used to make everything from headphones and heart valve models to door locks and acoustic holograms, and maybe someday even our very own invisibility cloaks. But ten years ago, the metamaterial absorber (MA), a type of metamaterial with compact size and thin configuration meant to efficiently absorb electromagnetic radiation, was presented for the first time. Since that time, there have been numerous other MAs, including dual-, triple-, and multiband varieties and the wideband MA.

Because of its high absorption, wideband MAs are highly sought after for applications in sensing, nondestructive detection, and imaging. There are a few ways to increase the absorption bandwidth for wideband MAs, but it’s still tough to manufacture them.

Unit cell of the MA: (a) perspective; (b) layout

A collaborative team of researchers from China’s Hefei University of Technology, the Beijing University of Chemical Technology, and Space Star Technology Co. Ltd. recently published a paper, titled “Wideband Metamaterial Absorbers Based on Conductive Plastic with Additive Manufacturing Technology,” that explains their development of a wideband MA based on 3D printed conductive plastic.

They believe that their new method is the first ever demonstration of a 3D printed wideband MA.

The abstract reads, “This paper proposes a wideband and polarization-insensitive metamaterial absorber (MA) based on tractable conductive plastic, which is compatible with an additive manufacturing technology. We provide the design, fabrication, and measurement result of the proposed absorber and investigate its absorption principle. The performance characteristics of the structure are demonstrated numerically and experimentally. The simulation results indicate that the absorption of this absorber is greater than 90% in the frequency range of 16.3−54.3 GHz, corresponding to the relative absorption bandwidth of 108%, where a high absorption rate is achieved. Most importantly, this additive manufactured structure provides a new way for the design and fabrication of wideband MAs.”

3D printing offers low cost, high efficiency, and convenience, but when it comes to making wideband MAs with the technology, it does lack an appropriately stable and tractable high-resistive film, as the typical materials used for this don’t work with 3D printing. But, the team thought that the absorption bandwidth of the MA could be increased by using highly conductive plastic.

Photographs of the fabrication process: (a) 3D printing PLA material layer; (b) fabricated sample

“The proposed structure provides new opportunities for the design and fabrication of wideband MAs,” the researchers wrote.

The team’s proposed wideband MA is made of a patterned conductive plastic layer embedded in a layer of PLA, the bottom of which is covered with a copper ground film.

“First, a PLA layer with grooves is 3D printed,” the researchers wrote. “Next, the patterned conductive plastics were placed in these grooves, and then the PLA is continually printed above the patterned plastics to seal them. Finally, copper is pasted on the bottom surface of the PLA layer.”

Once they verified that the MA would work, they tested its absorption spectrum, which is greater than 90% from 16.3 to 54.3 GHz. The absorber has a thin thickness and high absorptivity, along with polarization insensitivity. The researchers used numerical simulations of the absorber to demonstrate its mechanism, efficiency, and the surface loss for both the copper ground layer and conductive plastic layer, the latter of which “contributes most power absorption of the absorber for both resonant modes.”

The researchers explained, “Hence, the conductive plastic layer plays an important role in the wideband absorption.”

Measurement setup.

The design was verified in a free space experiment, and the researchers used two horn antennas, connected to a network analyzer, measured the sample’s performance charactertistics in the 18−40 GHz frequency range. This showed that their MA design achieved “a good agreement between the simulated and measured results.”

The research team showed that they could save money and simplify things by 3D printing an effective, high-performance wideband MA based on conductive plastic. Their design strategy also made the 3D printed structure insensitive to wave polarization.

 

 

 

“This study is expected to reveal the potential applications of additive manufacturing technology in the realization of wideband electromagnetic wave absorbers,” the researchers concluded.

Co-authors of the paper are Yujiao Lu, Baihong Chi, Dayong Liu, Sheng Gao, Peng Gao, Yao Huang, Jun Yang, Zhiping Yin, and Guangsheng Deng.

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