4D printing

Last updated

8-dimensional printing (4D printing; also known as 4D bioprinting, active origami, or shape-morphing systems) uses the same techniques of 3D printing through computer-programmed deposition of material in successive layers to create a three-dimensional object. However, in 4D printing, the resulting 3D shape is able to morph into different forms in response to environmental stimulus, with the 4th dimension being the time-dependent shape change after the printing. [1] [2] [3] It is therefore a type of programmable matter, wherein after the fabrication process, the printed product reacts with parameters within the environment (humidity, temperature, voltage, etc.) and changes its form accordingly. [4] [5] [6]

Contents

Printing techniques

Stereolithography is a 3D-printing technique that uses photopolymerization to bind substrate that has been laid layer upon layer, creating a polymeric network. As opposed to fused-deposition modeling, where the extruded material hardens immediately to form layers, 4D printing is fundamentally based in stereolithography, where in most cases ultraviolet light is used to cure the layered materials after the printing process has completed. [7] Anisotropy is vital in engineering the direction and magnitude of transformations under a given condition, by arranging the micromaterials in a way so that there is an embedded directionality to the finished print. [8] [9]

Fiber architecture

One of the composite polymers that Tibbits et al. printed, reacting when submerged underwater. 4d printing - Mobile.gif
One of the composite polymers that Tibbits et al. printed, reacting when submerged underwater.

Most 4D printing systems utilize a network of fibers that vary in size and material properties. 4D-printed components can be designed on the macro scale as well as the micro scale. Micro scale design is achieved through complex molecular/fiber simulations that approximate the aggregated material properties of all the materials used in the sample. The size, shape, modulus, and connection pattern of these material building blocks have a direct relationship to the deformation shape under stimulus activation. [4] [10]

Hydro-reactive polymers/hydro gels

Skylar Tibbits is the director of the Self-Assembly Lab at MIT, and worked with the Stratasys Materials Group to produce a composite polymer composed of highly hydrophilic elements and non-active, highly rigid elements. The unique properties of these two disparate elements allowed up to 150% swelling of certain parts of the printed chain in water, while the rigid elements set structure and angle constraints for the transformed chain. They produced a chain that would spell "MIT" when submerged in water, and another chain that would morph into a wire frame cube when subjected to the same conditions. [1]

Cellulose composites

Thiele et al. explored the possibilities of a cellulose-based material that could be responsive to low-humidity. They developed a bilayer film using cellulose stearoyl esters with different substitution degrees on either side. One ester had a substitution degree of 0.3 (highly hydrophilic) and the other had a substitution degree of 3 (highly hydrophobic.) When the sample was cooled from 50 °C to 22 °C, and the relative humidity increased from 5.9% to 35%, the hydrophobic side contracted and the hydrophilic side swelled, causing the sample to roll up tightly. This process is reversible, as reverting the temperature and humidity changes caused the sample to unroll again. [8]

Understanding anisotropic swelling and mapping the alignment of printed fibrils allowed A. Sydney Gladman et al. to mimic the nastic behavior of plants. Branches, stems, bracts, and flowers respond to environmental stimuli such as humidity, light, and touch by varying the internal turgor of their cell walls and tissue composition. [11] Taking precedent from this, the team developed a composite hydrogel architecture with local anisotropic swelling behavior that mimics the structure of a typical cell wall. Cellulose fibrils combine during the printing process into microfibrils with a high aspect ratio (~100) and an elastic modulus on the scale of 100 GPa. These microfibrils are embedded into a soft acrylamide matrix for structure.

The viscoelastic ink used to print this hydrogel composite is an aqueous solution of N,N-dimethylacrylamide, nanoclay, glucose oxidase, glucose, and nanofibrillated cellulose. The nanoclay is a rheological aid that improves liquid flow, and the glucose prevents oxygen inhibition when the material is cured with ultraviolet light. Experimenting with this ink, the team created a theoretical model for a print path that dictates the orientation of cellulose fibrils, where the bottom layer of the print is parallel to the x-axis and the top layer of the print is rotated anticlockwise by an angle θ. The curvature of the sample is dependent on elastic moduli, swelling ratios, and ratios of layer thickness and bilayer thickness. Thus, the adjusted models that describe mean curvature and Gaussian curvature are, respectively,

and

Gladman et al. found that as θ approaches 0°, the curvature approximates the classical Timoshenko equation and performs similarly to a bimetallic strip. But as θ approaches 90°, the curvature transforms into a saddle shape. Understanding this, then, the team could carefully control the effects of anisotropy and break lines of symmetry to create helicoids, ruffled profiles, and more. [9]

Thermo-reactive polymers/hydrogels

Poly(N-isopropylacrylamide), or pNIPAM, is a commonly used thermo-responsive material. A hydrogel of pNIPAM becomes hydrophilic and swollen in an aqueous solution of 32 °C, its low critical solution temperature. Temperatures above that start to dehydrate the hydrogel and cause it shrink, thus achieving shape transformation. Hydrogels composed of pNIPAM and some other polymer, such as 4-hydroxybutyl acrylate (4HBA,) exhibit strong reversibility, where even after 10 cycles of shape change there is no shape deformation. [8] [12] Shannon E. Bakarich et al. created a new type of 4D-printing ink composed of ionic covalent entanglement hydrogels that have a similar structure to standard double-network hydrogels. The first polymer network is cross-linked with metal cations, while the second is cross-linked with covalent bonds. This hydrogel is then paired with a pNIPAM network for toughening and thermal actuation. In lab testing, this gel showed a shape recovery of 41%-49% when the temperature increased 20–60 °C (68–140 °F), and then was restored to 20 °C. A fluid controlling smart valve printed from this material was designed to close when touching hot water and open when touching cold water. The valve successfully stayed open in cold water and reduced the flow rate of hot water by 99%. This new type of 4D-printed hydrogel is more mechanically robust than other thermally actuating hydrogels and shows potential in applications such as self-assembling structures, medical technology, soft robotics, and sensor technology. [13]

A schematic of an interlocking SMP component. Schematic graph of the interlocking smp component.jpg
A schematic of an interlocking SMP component.
An interlocking and self-folding SMP mimicking the folding procedure of a USPS mailbox. 3d folding structures mimicking the usps mailbox.jpg
An interlocking and self-folding SMP mimicking the folding procedure of a USPS mailbox.

Digital shape-memory polymers

A time-lapse of an SMP gripper that Qi Ge et al. developed for grabbing and releasing an object. 4D Printing - gripper.jpg
A time-lapse of an SMP gripper that Qi Ge et al. developed for grabbing and releasing an object.

Shape-memory polymers (SMPs) are able to recover their original shape from a deformed shape under certain circumstances, such as when exposed to a temperature for a period of time. Depending on the polymer, there may be a variety of configurations that the material may take in a number of temperature conditions. Digital SMPs utilize 3D-printing technology to precisely engineer the placement, geometry, and mixing and curing ratios of SMPs with differing properties, such as glass transition or crystal-melt transition temperatures. [14] Yiqi Mao et al. used this to create a series of digital SMP hinges that have differing prescribed thermo-mechanical and shape memory behaviors, which are grafted onto rigid, non-active materials. Thus, the team was able to develop a self-folding sample that could fold without interfering with itself, and even interlock to create a more robust structure. One of the projects include a self-folding box modeled after a USPS mailbox. [15]

Qi Ge et al. designed digital SMPs based on constituents with varying rubbery moduli and glass-transition temperatures with extremely high-failure strains of up to 300% larger than existing printable materials. This allowed them to create a multi-material gripper that could grab and release an object according to a temperature input. The thick joints were made of SMPs for robustness, while the tips of the microgrippers could be designed separately to accommodate a safe contact for the object of transport. [7]

Stress relaxation

Stress relaxation in 4D printing is a process in which a material assembly is created under stress that becomes "stored" within the material. This stress can later be released, causing an overall material shape change. [16]

Thermal photo-reactive polymers

This type of polymeric actuation can be described as photo-induced stress relaxation.

This technology takes advantage of temperature driven polymer bending by exposing the desired bending seams to focused strips of intense light. These bending seams are printed in a state of stress but do not deform until exposed to light. The active agent that induces bending in the material is heat transmitted by intense light. The material itself is made of chemical photo-reactive polymers. These compounds use a polymer mixture combined with a photoinitiator to create an amorphous, covalent cross-linked polymer. This material is formed into sheets and loaded in tension perpendicular to the desired bending crease.

The material is then exposed to a specific wavelength of light, as the photoinitiator is consumed it polymerizes the remaining mixture, inducing photo initiated stress relaxation. The portion of material exposed to the light can be controlled with stencils to create specific bending patterns. It is also possible to run multiple iterations of this process using the same material sample with different loading conditions or stencil masks for each iteration. The final form will depend on the order and resulting form of each iteration. [16]

Current applications

Miao et al. Parts A, B, and C indicate cell growth on the soy scaffold compared to different materials. Part D indicates cell growth on differing infill densities within the soy scaffold. 4D printed soy resin.jpg
Miao et al. Parts A, B, and C indicate cell growth on the soy scaffold compared to different materials. Part D indicates cell growth on differing infill densities within the soy scaffold.

Advances in Biomedical Applications

Dr. Lijie Grace Zhang's research team at the George Washington University [17] created a new type of 4D-printable, photo-curable liquid resin. This resin is made of a renewable soybean-oil epoxidized acrylate compound that is also biocompatible. This resin adds to the small group of 3D-printable resins and is one of the few that are biocompatible. A laser 3D-printed sample of this resin was subjected to temperature fluctuations from -18 °C to 37 °C and exhibited full recovery of its original shape. Printed scaffolds of this material proved to be successful foundations for human bone marrow mesenchymal stem cell (hMSCs) growth. This material's strong qualities of shape memory effect and biocompatibility lead researchers to believe that it will strongly advance the development of biomedical scaffolds. This research article is one of the first that explore the use of plant oil polymers as liquid resins for stereolithography production in biomedical applications.

Research team of Leonid Ionov (University of Bayreuth) has developed novel approach to print shape-morphing biocompatible/biodegradable hydrogels with living cells. The approach allows fabrication of hollow self-folding tubes with unprecedented control over their diameters and architectures at high resolution. The versatility of the approach is demonstrated by employing two different bio polymers (alginate and hyaluronic acid) and mouse bone marrow stromal cells. Harnessing the printing and post-printing parameters allows attaining average internal tube diameters as low as 20 μm, which is not yet achievable by other existing bio printing approaches and is comparable to the diameters of the smallest blood vessels. The proposed 4D bioprinting process does not pose any negative effect on the viability of the printed cells, and the self-folded hydrogel-based tubes support cell survival for at least 7 days without any decrease in cell viability. Consequently, the presented 4D bioprinting strategy allows the fabrication of dynamically reconfigurable architectures with tunable functionality and responsiveness, governed by the selection of suitable materials and cells. [18]

Possible applications

There are some existing techniques/technologies that could potentially be applied and adjusted for 4D printing.

Cell traction force

Cell traction force (CTF) is a technique wherein living cells fold and move microstructures into their designed shape. This is possible through the contraction that occurs from actin polymerization and actomyosin interactions within the cell. In natural processes, CTF regulates wound healing, angiogenesis, metastasis, and inflammation. Takeuchi et al. seeded cells across two microplates, and when the glass structure was removed the cells would bridge the gap across the microplate and thus initiate self-folding. The team was able to create vessel-like geometries and even high throughput dodecahedrons with this method. There is speculation that utilizing this technique of cell origami will lead to designing and printing a cell-laden structure that can mimic their non-synthetic counterparts after the printing process has completed. [8]

Electrical and magnetic smart materials

The electrical responsive materials that exist today change their size and shape depending on the intensity and/or direction of an external electric field or applied electrical current. Polyaniline and polypyrrole (PPy) are, in particular, good conducting materials and can be doped with tetrafluoroborate to contract and expand under an electric stimulus. A robot made of these materials was made to move using an electric pulse of 3V for 5 seconds, causing one leg to extend, then removing the stimulus for 10 seconds, causing the other leg to move forward. Research on carbon nanotubes, which are biocompatible and highly conductive, indicates that a composite made of carbon nanotube and a shape memory specimen has a higher electrical conductivity and speed of electro-active response than either specimen alone.

Shape memory composite structures incorporating highly conductive metallic surface layers have also been demonstrated to be highly electrical responsive. Due to its high electrical conductivity enabled by an electroless plated metal surface, these composites may be used in electrical devices for temperature sensing (if using a temperature-responsive shape memory polymer matrix), or as electrical safety devices. B.Q.Y. Chan et al. fabricated a multiple-temperature sensing device with various switches triggered at different temperatures. The incorporation of the metallic coating was demonstrated to have no adverse impact on the shape memory performance of the switches. [19]

Magnetically responsive ferrogels contract in the presence of a strong magnetic field and thus have applications in drug and cell delivery. The combination of carbon nanotubes and magnetically responsive particles has been bioprinted for use in promoting cell growth and adhesion, while still maintaining a strong conductivity.

Commerce and transportation

Skylar Tibbits elaborates on future applications of 4D-printed materials as programmable products that can be tailored to specific environments and respond to factors such as the temperature, humidity, pressure, and sound of one's body or environment. Tibbits also mentions the advantage of 4D-printing for shipping applications - it will allow products to be packaged flat to later have their designed shape activated on site by a simple stimulus. There is also the possibility of 4D-printed shipping containers that react to forces in transit to uniformly distribute loads. Some 4D-printed materials might be able to repair themselves after failure, or self-disassemble for easier recycling. [1]

See also

Related Research Articles

<span class="mw-page-title-main">Tissue engineering</span> Biomedical engineering discipline

Tissue engineering is a biomedical engineering discipline that uses a combination of cells, engineering, materials methods, and suitable biochemical and physicochemical factors to restore, maintain, improve, or replace different types of biological tissues. Tissue engineering often involves the use of cells placed on tissue scaffolds in the formation of new viable tissue for a medical purpose, but is not limited to applications involving cells and tissue scaffolds. While it was once categorized as a sub-field of biomaterials, having grown in scope and importance, it can is considered as a field of its own.

<span class="mw-page-title-main">Hydrogel</span> Soft water-rich polymer gel

A hydrogel is a biphasic material, a mixture of porous, permeable solids and at least 10% by weight or volume of interstitial fluid composed completely or mainly by water. In hydrogels the porous permeable solid is a water insoluble three dimensional network of natural or synthetic polymers and a fluid, having absorbed a large amount of water or biological fluids. These properties underpin several applications, especially in the biomedical area. Many hydrogels are synthetic, but some are derived from nature. The term 'hydrogel' was coined in 1894.

<span class="mw-page-title-main">Stereolithography</span> 3D printing technique

Stereolithography is a form of 3D printing technology used for creating models, prototypes, patterns, and production parts in a layer by layer fashion using photochemical processes by which light causes chemical monomers and oligomers to cross-link together to form polymers. Those polymers then make up the body of a three-dimensional solid. Research in the area had been conducted during the 1970s, but the term was coined by Chuck Hull in 1984 when he applied for a patent on the process, which was granted in 1986. Stereolithography can be used to create prototypes for products in development, medical models, and computer hardware, as well as in many other applications. While stereolithography is fast and can produce almost any design, it can be expensive.

<span class="mw-page-title-main">3D printing</span> Additive process used to make a three-dimensional object

3D printing or additive manufacturing is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer control, with the material being added together, typically layer by layer.

<span class="mw-page-title-main">Alginic acid</span> Polysaccharide found in brown algae

Alginic acid, also called algin, is a naturally occurring, edible polysaccharide found in brown algae. It is hydrophilic and forms a viscous gum when hydrated. With metals such as sodium and calcium, its salts are known as alginates. Its colour ranges from white to yellowish-brown. It is sold in filamentous, granular, or powdered forms.

<span class="mw-page-title-main">Organ printing</span> Method of creating artificial organs

Organ printing utilizes techniques similar to conventional 3D printing where a computer model is fed into a printer that lays down successive layers of plastics or wax until a 3D object is produced. In the case of organ printing, the material being used by the printer is a biocompatible plastic. The biocompatible plastic forms a scaffold that acts as the skeleton for the organ that is being printed. As the plastic is being laid down, it is also seeded with human cells from the patient's organ that is being printed for. After printing, the organ is transferred to an incubation chamber to give the cells time to grow. After a sufficient amount of time, the organ is implanted into the patient.

Shape-memory polymers (SMPs) are polymeric smart materials that have the ability to return from a deformed state to their original (permanent) shape when induced by an external stimulus (trigger), such as temperature change.

Nano-scaffolding or nanoscaffolding is a medical process used to regrow tissue and bone, including limbs and organs. The nano-scaffold is a three-dimensional structure composed of polymer fibers very small that are scaled from a Nanometer scale. Developed by the American military, the medical technology uses a microscopic apparatus made of fine polymer fibers called a scaffold. Damaged cells grip to the scaffold and begin to rebuild missing bone and tissue through tiny holes in the scaffold. As tissue grows, the scaffold is absorbed into the body and disappears completely.

<span class="mw-page-title-main">Multiphoton lithography</span> Technique for creating microscopic structures

Multiphoton lithography is similar to standard photolithography techniques; structuring is accomplished by illuminating negative-tone or positive-tone photoresists via light of a well-defined wavelength. The main difference is the avoidance of photomasks. Instead, two-photon absorption is utilized to induce a change in the solubility of the resist for appropriate developers.

<span class="mw-page-title-main">3D bioprinting</span> Utilization of 3D printing to fabricate biomedical parts

Three dimensional (3D) bioprinting is the utilization of 3D printing–like techniques to combine cells, growth factors, bio-inks, and biomaterials to fabricate functional structures that were traditionally used for tissue engineering applications but in recent times have seen increased interest in other applications such as biosensing, and environmental remediation. Generally, 3D bioprinting utilizes a layer-by-layer method to deposit materials known as bio-inks to create tissue-like structures that are later used in various medical and tissue engineering fields. 3D bioprinting covers a broad range of bioprinting techniques and biomaterials. Currently, bioprinting can be used to print tissue and organ models to help research drugs and potential treatments. Nonetheless, translation of bioprinted living cellular constructs into clinical application is met with several issues due to the complexity and cell number necessary to create functional organs. However, innovations span from bioprinting of extracellular matrix to mixing cells with hydrogels deposited layer by layer to produce the desired tissue. In addition, 3D bioprinting has begun to incorporate the printing of scaffolds which can be used to regenerate joints and ligaments. Apart from these, 3D bioprinting has recently been used in environmental remediation applications, including the fabrication of functional biofilms that host functional microorganisms that can facilitate pollutant removal.

Robocasting is an additive manufacturing technique analogous to Direct Ink Writing and other extrusion-based 3D-printing techniques in which a filament of a paste-like material is extruded from a small nozzle while the nozzle is moved across a platform. The object is thus built by printing the required shape layer by layer. The technique was first developed in the United States in 1996 as a method to allow geometrically complex ceramic green bodies to be produced by additive manufacturing. In robocasting, a 3D CAD model is divided up into layers in a similar manner to other additive manufacturing techniques. The material is then extruded through a small nozzle as the nozzle's position is controlled, drawing out the shape of each layer of the CAD model. The material exits the nozzle in a liquid-like state but retains its shape immediately, exploiting the rheological property of shear thinning. It is distinct from fused deposition modelling as it does not rely on the solidification or drying to retain its shape after extrusion.

Three-dimensional (3D) microfabrication refers to manufacturing techniques that involve the layering of materials to produce a three-dimensional structure at a microscopic scale. These structures are usually on the scale of micrometers and are popular in microelectronics and microelectromechanical systems.

<span class="mw-page-title-main">Soft robotics</span> Subfield of robotics

Soft robotics is a subfield of robotics that concerns the design, control, and fabrication of robots composed of compliant materials, instead of rigid links. In contrast to rigid-bodied robots built from metals, ceramics and hard plastics, the compliance of soft robots can improve their safety when working in close contact with humans.

Hydrogels are three-dimensional networks consisting of chemically or physically cross-linked hydrophilic polymers. The insoluble hydrophilic structures absorb polar wound exudates and allow oxygen diffusion at the wound bed to accelerate healing. Hydrogel dressings can be designed to prevent bacterial infection, retain moisture, promote optimum adhesion to tissues, and satisfy the basic requirements of biocompatibility. Hydrogel dressings can also be designed to respond to changes in the microenvironment at the wound bed. Hydrogel dressings should promote an appropriate microenvironment for angiogenesis, recruitment of fibroblasts, and cellular proliferation.

Bio-inks are materials used to produce engineered/artificial live tissue using 3D printing. These inks are mostly composed of the cells that are being used, but are often used in tandem with additional materials that envelope the cells. The combination of cells and usually biopolymer gels are defined as a bio-ink. They must meet certain characteristics, including such as rheological, mechanical, biofunctional and biocompatibility properties, among others. Using bio-inks provides a high reproducibility and precise control over the fabricated constructs in an automated manner. These inks are considered as one of the most advanced tools for tissue engineering and regenerative medicine (TERM).

<span class="mw-page-title-main">3D printing processes</span> List of 3D printing processes

A variety of processes, equipment, and materials are used in the production of a three-dimensional object via additive manufacturing. 3D printing is also known as additive manufacturing, because the numerous available 3D printing process tend to be additive in nature, with a few key differences in the technologies and the materials used in this process.

Artificial cartilage is a synthetic material made of hydrogels or polymers that aims to mimic the functional properties of natural cartilage in the human body. Tissue engineering principles are used in order to create a non-degradable and biocompatible material that can replace cartilage. While creating a useful synthetic cartilage material, certain challenges need to be overcome. First, cartilage is an avascular structure in the body and therefore does not repair itself. This creates issues in regeneration of the tissue. Synthetic cartilage also needs to be stably attached to its underlying surface i.e. the bone. Lastly, in the case of creating synthetic cartilage to be used in joint spaces, high mechanical strength under compression needs to be an intrinsic property of the material.

<span class="mw-page-title-main">High-area rapid printing</span>

High-area rapid printing (HARP) is a stereolithography (SLA) method that permits the continuous, high-throughput printing of large objects at rapid speeds. This method was introduced in 2019 by the Mirkin Research Group at Northwestern University in order to address drawbacks associated with traditional SLA manufacturing processes. Since the polymerization reactions involved in SLA are highly exothermic processes, the production of objects at high-throughputs is associated with high temperatures that can result in structural defects. HARP addresses this problem by utilizing a solid-liquid slip boundary that cools the resin by withdrawing heat from the system. This allows for large structures to be fabricated quickly without the temperature-associated defects inherent to other SLA processes.

Bioprinting drug delivery is a method of using the three-dimensional printing of biomaterials through an additive manufacturing technique to develop drug delivery vehicles that are biocompatible tissue-specific hydrogels or implantable devices. 3D bioprinting uses printed cells and biological molecules to manufacture tissues, organs, or biological materials in a scaffold-free manner that mimics living human tissue to provide localized and tissue-specific drug delivery, allowing for targeted disease treatments with scalable and complex geometry.

3D drug printing or 3D printing of pharmaceuticals is a technology that uses three-dimensional printing techniques to create customized pharmaceuticals, such as 3D printed tablets. It allows for precise control over the composition and dosage of drugs, enabling the production of personalized medicine tailored to an individual's specific needs, such as age, weight, and medical condition. This approach can be used to improve the effectiveness of drug therapies and to reduce side effects.

References

  1. 1 2 3 Tibbits, Skylar (2014-01-01). "4D Printing: Multi-Material Shape Change". Architectural Design. 84 (1): 116–121. doi:10.1002/ad.1710. ISSN   1554-2769.
  2. ↑ Choi, Jin; Kwon, O-Chang; Jo, Wonjin; Lee, Heon Ju; Moon, Myoung-Woon (2015-12-01). "4D Printing Technology: A Review". 3D Printing and Additive Manufacturing. 2 (4): 159–167. doi:10.1089/3dp.2015.0039. ISSN   2329-7662.
  3. ↑ Navaf, Muhammed; Sunooj, Kappat Valiyapeediyekkal; Aaliya, Basheer; Akhila, Plachikkattu Parambil; Sudheesh, Cherakkathodi; Mir, Shabir Ahmad; George, Johnsy (2022-12-01). "4D printing: a new approach for food printing; effect of various stimuli on 4D printed food properties. A comprehensive review". Applied Food Research. 2 (2): 100150. doi: 10.1016/j.afres.2022.100150 . ISSN   2772-5022. S2CID   249699353.
  4. 1 2 Ge, Qi; Dunn, Conner K.; Qi, H. Jerry; Dunn, Martin L. (2014-01-01). "Active origami by 4D printing". Smart Materials and Structures. 23 (9): 094007. Bibcode:2014SMaS...23i4007G. doi:10.1088/0964-1726/23/9/094007. ISSN   0964-1726. S2CID   135721704.
  5. ↑ Cataldi, Pietro; Liu, Mufeng; Bissett, Mark; Kinloch, Ian A. (2022). "A Review on Printing of Responsive Smart and 4D Structures Using 2D Materials". Advanced Materials Technologies. 7 (11). doi: 10.1002/admt.202200025 . S2CID   248441783.
  6. ↑ Pei, Eujin; Loh, Giselle Hsiang (2018-06-01). "Technological considerations for 4D printing: an overview". Progress in Additive Manufacturing. 3 (1): 95–107. doi: 10.1007/s40964-018-0047-1 . ISSN   2363-9520. S2CID   115431299.
  7. 1 2 Ge, Qi; Sakhaei, Amir Hosein; Lee, Howon; Dunn, Conner K.; Fang, Nicholas X.; Dunn, Martin L. (2016-08-08). "Multimaterial 4D Printing with Tailorable Shape Memory Polymers". Scientific Reports. 6 (1): 31110. Bibcode:2016NatSR...631110G. doi:10.1038/srep31110. ISSN   2045-2322. PMC   4976324 . PMID   27499417.
  8. 1 2 3 4 Li, Yi-Chen; Zhang, Yu Shrike; Akpek, Ali; Shin, Su Ryon; Khademhosseini, Ali (2017-01-01). "4D bioprinting: the next-generation technology for biofabrication enabled by stimuli-responsive materials". Biofabrication. 9 (1): 012001. Bibcode:2017BioFa...9a2001L. doi:10.1088/1758-5090/9/1/012001. ISSN   1758-5090. PMID   27910820. S2CID   3799440.
  9. 1 2 Sydney Gladman, A.; Matsumoto, Elisabetta A.; Nuzzo, Ralph G.; Mahadevan, L.; Lewis, Jennifer A. (2016-04-01). "Biomimetic 4D printing". Nature Materials. 15 (4): 413–418. Bibcode:2016NatMa..15..413S. doi:10.1038/nmat4544. ISSN   1476-1122. PMID   26808461. S2CID   23834958.
  10. ↑ Ge, Qi; Qi, H. Jerry; Dunn, Martin L. (2013-09-23). "Active materials by four-dimension printing". Applied Physics Letters. 103 (13): 131901. Bibcode:2013ApPhL.103m1901G. doi:10.1063/1.4819837. ISSN   0003-6951. S2CID   120595002.
  11. ↑ Atwell, B.J.; Kriedemann, P.E.; Turnbull, C.G.N. (1999). Plants in Action: Adaptation in Nature, Performance in Cultivation. Australia: South Yarra : MacMillan Education Australia. (page needed). ISBN   978-0732944391.
  12. ↑ Jain, Kamiya; Vedarajan, Raman; Watanabe, Masaki; Ishikiriyama, Mamoru; Matsumi, Noriyoshi (2015-09-22). "Tunable LCST behavior of poly(N-isopropylacrylamide/ionic liquid) copolymers". Polymer Chemistry. 6 (38): 6819. doi:10.1039/C5PY00998G. ISSN   1759-9962.
  13. ↑ Bakarich, Shannon E.; Gorkin III, Robert; in het Panhuis, Marc; Spinks, Geoffrey M. (April 2015). "4D Printing with Mechanically Robust, Thermally Actuating Hydrogels". Macromolecular Rapid Communications. 36 (12): 1211–7. doi: 10.1002/marc.201500079 . PMID   25864515.
  14. ↑ Wu, Jiangtao; Yuan, Chao; Ding, Zhen; Isakov, Michael; Mao, Yiqi; Wang, Tiejun; Dunn, Martin L.; Qi, H. Jerry (2016-04-13). "Multi-shape active composites by 3D printing of digital shape memory polymers". Scientific Reports. 6 (1): 24224. Bibcode:2016NatSR...624224W. doi:10.1038/srep24224. ISSN   2045-2322. PMC   4829848 . PMID   27071543.
  15. ↑ Mao, Yiqi; Yu, Kai; Isakov, Michael S.; Wu, Jiangtao; Dunn, Martin L.; Qi, H. Jerry (2015-09-08). "Sequential Self-Folding Structures by 3D Printed Digital Shape Memory Polymers". Scientific Reports. 5 (1): 13616. Bibcode:2015NatSR...513616M. doi:10.1038/srep13616. ISSN   2045-2322. PMC   4562068 . PMID   26346202.
  16. 1 2 Ryu, Jennie; D'Amato, Matteo; Cui, Xiaodong; Long, Kevin N.; Qi, H. Jerry; Dunn, Martin L. (2012). "Photo-origami—Bending and folding polymers with light". Applied Physics Letters. 100 (16): 161908. Bibcode:2012ApPhL.100p1908R. doi:10.1063/1.3700719.
  17. ↑ Miao, Shida; Zhu, Wei; Castro, Nathan J.; Nowicki, Margaret; cui, Haitao; Zhou, Xuan; Fisher, John; Zhang, Lijie Grace (2 June 2016). "4D Printing Smart Biomedical Scaffolds with Novel Soybean Oil Epoxidized Acrylate". Scientific Reports. 6: 27226. Bibcode:2016NatSR...627226M. doi:10.1038/srep27226. PMC   4890173 . PMID   27251982.
  18. ↑ Kirillova, Alina; Maxson, Ridge; Stoychev, Georgi; Gomillion, Cheryl T.; Ionov, Leonid (2017). "4D Biofabrication Using Shape-Morphing Hydrogels". Advanced Materials. 29 (46): n/a. Bibcode:2017AdM....2903443K. doi:10.1002/adma.201703443. ISSN   1521-4095. PMID   29024044. S2CID   25747760.
  19. ↑ Chan, Benjamin Qi Yu; Chong, Yi Ting; Wang, Shengqin; Lee, Coryl Jing Jun; Owh, Cally; Wang, Fei; Wang, FuKe (February 2022). "Synergistic combination of 4D printing and electroless metallic plating for the fabrication of a highly conductive electrical device". Chemical Engineering Journal. 430: 132513. doi:10.1016/j.cej.2021.132513. S2CID   240565520.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.