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4D Printing as a Time Dependent 3D Printing

Curator: Danut Dragoi, PhD
The 4D printing can be explained based on 3D printing, whose concept is shown in here.

It has an extra added dimension like time, or any implicit time variable included in any environmental physical parameter like

• temperature,
• pressure,
• moisture or humidity,
• external/internal electric field and or
• magnetic field.

This is not a true 4D space in the sense X,Y,Z,t — it is a parameterized printing process in which each variable X(t), Y(t), Z(t)  is a function of time. Therefore,it is an object that has its shape defined by a surface with variables that depends of time. This reminds us about smart shape memory  materials. Today there are not only metallic smart materials but also shape-memory polymers that have similar behavior of smart metallic shape memory materials. It is interesting to add that many  polymeric smart materials have a response to a given stimuli like moisture, electric field, etc. To produce some 3D objects with a shape dependent of time we just need these special polymers. The reason for adding a new parameter as an extra dimension is in the need to reach complex topological object. Skylar Tibbits, who is a mathematician at MIT, proposed 4D printing in a TED talk. The 4D printing concept can be better understood from examples. The folding of a strand of eight segments can transform from a line to a cube shape. The researcher in Australia created a valve using 4D printing  The valve is sensitive to temperature, it closes when the water is hot and opens when it is cold. A graphical explanation of 4D printing is explained here. All these examples show a promising starting level of technology readiness. The authors published their 4D printing concepts and results on TED events. As the main characteristic of these events is the entertainment of the audience, the right assessment of the 4D technology is awaiting the words of the specialists through the scientific pair reviewed papers. One important question for 4D printed human organs is that of life time circle of the printed organ and possible rejection. Since the material of the 4D printed objects is a polymer or a combination of polymers, we expect a low time cicle due to low fatigue characteristic of these materials.The question arises as to what exactly 4D printing will add as extra to the already existing technology of 3D printing at hand? The answer is the whole new dimension i.e time we added. If we consider a smart combination of materials that produce periodic shape change, such as the case of the heart, than we have a possible solution for 4D printing of the heart. But again the fatigue issue has to be taken into consideration again. The scientists can also give an object the ability to alter its shape and to fold itself  through self assembling molecules when the effect of temperature and pressure is considered. Other impact factors should be considered when the environment is the interior of the human body where the influence of temperature, pressure or other variable factors such as vibrations, etc. can play an important role. As a conclusion of this posting we can state that the 4D printing is at its beginning, it is not a true 4 dimensional space as the title of this method suggests.The fourth dimension time in 4D tittle is lost in the polymeric material behavior when it is influenced by a stimuli such as moisture, temperature, pressure, etc. The property of molecules, large or small to self-assemble is associated with the shape change that is exploited in the 4D printing.