The Twilight Zone: Printing in the 4th Dimension

In the April issue of Metropolis Magazine an article titled “Source Material” (previously mentioned here) discusses a concept they call 4D printing.  Of course the first question that comes to mind is- how can an object have a FOURTH dimension when the world only exists in 3 dimensions?  Well, I hate to be the bearer of bad news, but we live in a four dimensional world.   In a 3 dimensional world, if i were going to make an appointment to meet you, i would specify 3 dimensions:  how far North-South (i.e. 34th st), East-West (6th Avenue) and the elevation (third floor) also known as the X Y and Z axes.  But in the real world, this would make for pretty lousy planning.  I’ve told you where to meet me, but I haven’t told you WHEN.  The fourth dimension of our universe is time.


So 4D printing involves creating an object that changes in time based on some external stimulus.  It sounds very complex but it’s surprisingly simple when you wrap your head around it.  For instance, in a simple way, any product that has moving parts involves the fourth dimension of design.  So in a way 4D printing has been with us as along as 3D printing in the form of printed hinges and flexible materials.  But I guess you could call this “passive 4D” because the product only changes with time in a direct way when an agent (i.e. a person) acts upon it.

Left:  How the file looks with the components interlocking.  Right:  3D printed earrings acted upon by gravity.  Available at
3D Sphere Earrings by DESiGNERiCA. Left: How the file looks with the components interlocking. Right: 3D printed earrings acted upon by gravity. Available on my website.

For instance, my nylon earring designs are all printed as a single unit from powdered nylon.  Each individual shape is printed interlocking with its neighbors but not touching.  They are supported and kept separate during the printing process by unmelted nylon powder.   When the print is complete, the series of solid interlocking forms is removed from the powder and each link falls to rest on its neighbor like a chain.

Kinematics Dress by Nervous System via Shapeways
Kinematics Dress by Nervous System via Shapeways

The next step in “passive” 4D printing came from the ever-brilliant minds of Jessica Rosenkrantz and Jesse Louis-Rosenberg  over at Nervous System.  In November 2013 the team introduced a system and accompanying wearable collection called Kinematics which facilitates the design of large 3D printable items that fold and compress to be printable in a  much smaller area than the size of the object would imply .  This is achieved by designing a product made from smaller hinged panels that enable the part to unfold after printing.

“Kinematics is a system for 4D printing that creates complex, foldable forms composed of articulated modules. The system provides a way to turn any three-dimensional shape into a flexible structure using 3D printing. Kinematics combines computational geometry techniques with rigid body physics and customization. Practically, Kinematics allows us to take large objects and compress them down for 3D printing through simulation. It also enables the production of intricately patterned wearables that conform flexibly to the body.” [Nervous System Blog, 11/26/13]

It’s a lot like when you wad up a t-shirt into a ball– it occupies the same amount of space as it does when you lay it out flat, but it fits into a much smaller box.  This is the first step in 4D printing– objects that move, bend, and fold.

A 4D printed Octahedron from Metropolis Magazine
A 4D printed Octahedron from Metropolis Magazine

But the Metropolis article introduced me to a concept that I’m going to call “responsive” or “active” 4D printing.   This seriously blew my mind when i heard it, but when i really started to think about it I found analogs in nature, as usual.  Apparently Skylar Tibbits of SJET.US is trying  “to create active printed structures that can transform and reconfigure—change shape, appearance, and properties. Therefore, they become actuators, sensors, and physical computing devices” (Metropolis Magazine, April 2014).  In other words, these would be objects that can change based on outside stimulus more intricate than simply a hand pushing a hinge closed.  These objects involve the layering of different materials in different configurations that would react differently in different environments causing a change based not on an active outside influence, but on, for instance, a change in humidity, temperature or other environmental factor.

Lets look at some non-printed examples.  Lets say you made a striped blanket by cutting strips of two different fabrics and sewing them back together by alternating the two materials: one red and one blue.  But you failed to consider that, while both materials are made of cotton, the red material has been pre-shrunk and the blue has not.  What happens when you wash and dry your striped blanket?  The red panels stay the same size, but the blue panels now shrink, causing the seams and the red panels to gather, and your blanket is no longer as big as it was.   It has changed in the fourth dimension, not just the positions of the parts relative to one another,  not just because you pushed or pulled on it, the internal structure of one part has changed (shrunk), causing a change in the overall shape of the object.

The second example will be familiar to anyone with curly hair.  Curly hair changes shape based on the ambient humidity.  We usually call it frizz and get annoyed, but imagine if this idea could be used to tell a humidifier when to turn on or off or when the garden sprinklers should turn on.  This would allow a single 3D printed object to take the place of complex electronics.

A series of time-lapse images showing a 4-D printed self- folding 50-foot strand as it transforms in water.  via Metropolis Mag
A series of time-lapse images showing a 4-D printed self- folding 50-foot strand as it transforms in water. via Metropolis Magazine

The article includes this  compelling series of photographs of a 3D printed item “self-assembling” in water.  If you can imprint shrinkage and flexibility on a material that is dependent upon an external factor you could create truly responsive materials.  Imagine a tile which, when wet, changes shape to channel the water to a specific place and provide traction but becomes flat and easy to clean when dry.   Or maybe you could print a flat sheet (easy to transport, stack, etc.) that turns into a lounge chair when you put it into the sun.    Think that sounds like science fiction?  Well, yeah, but it’s about to be science fact.  Witness:

4D Printing: Cube Self-Folding Strand from Skylar Tibbits on Vimeo.

Responsive or “active” 4D printing is without a doubt the future of manufacturing.  Once readily available machines are able to apply multiple materials to a single print, which is bound to happen within the next few years, the next wave of innovation will go beyond experimenting with different materials to experimenting with how the different materials can influence each other, and the possibilities will suddenly grow exponentially.

WTF is 3D Printing?



Despite all the articles about 3D printing technologies, I know a lot of people are less than clear as to what the term even means.  I’ve had some luck explaining it to lay people, so I thought I’d offer that explanation the world in written form for future reference.


To begin with, you have to understand that 3D Printing DOES NOT REFER TO A SINGLE TECHNOLOGY.  Rather, it’s a catch-all phrase for a set of new technologies that can also be called “additive manufacturing” or “rapid prototyping” (RP).  RP is a somewhat outdated term stemming from a  time when 3D printing was so limited and expensive that it was only useful for making non-functional prototypes.  As this is no longer true, I’m not going to use this term again.  The term additive manufacturing is much more useful, and simply refers to the fact that a form is created by adding successive layers of material.  The opposite would be subtractive manufacturing which is essentially the same as carving or whittling and when done by a computer-controlled machine is called CNC (computer numerical control)


Every 3D print begins as a 3-dimensional computer file.  This can be created using 3D modeling software or by 3D scanning an existing form.  To prepare the file for printing, the computer chops the form up into a series of successive 2D shapes.  Imagine you sliced a vegetable into really thin slices and then were able to put them back together to re-form the vegetable.  Kind of like an MRI scan, where a series of flat images are used to create a video as if you’re moving “through” the object.  Like this:





Once the computer “slices” the form, it’s time to put the flat slices back together to make the a 3 dimensional form.  The most basic 3D printers like MakerBot and other home models utilize extruded plastic and operate a lot like a tiny glue gun.  Hard plastic is fed into into one end, the other end melts it and lays it down as it moves across a flat surface.   The computer tells the printer head (glue gun) when to turn off an on and how to move around the printer bed to “draw” the first slice.  The resolution of the print will be determined by the thickness of the extruded plastic.  Once the first “slice” has been drawn, the printer bed drops down the thickness of one slice and the process is repeated, drawing the second slice on top of the first, the third on top of the second, etc. until the whole 3-dimensional form is complete.

All 3D printing technologies work by applying successive layers in a pre-determined pattern to create a 3 dimensional form.  The differences between the technologies are in the form of the building material and the way it is adhered.  Starting with liquid plastic (like the extrusion process) only allows for relatively low-resolution prints, because you can only get the plastic so thin before it begins to break.  In order to get high resolutions and hence smoother products, different materials and technologies are employed to create the slices.


SLS or Selective Laser Sintering is another printing technology.  Here, the entire print bed is covered with a very thin layer of powdered material (often nylon).  Rather than a glue gun, the print head is equipped with a laser, which “draws” the shape of the “slice” onto the powder.  As the laser moves, it melts the layer of powder directly under it, turning only that powder into a solid.  Another thin layer of powder is applied over the first, and the laser traces the second slice with such precision as to not melt the layer below.  This is repeated until the final product– a solid form– has been formed within a bed of powder.  The solid piece is then removed and cleaned of excess powder.

Metal Printing

There are also other ways that this process can be achieved.  For instance, some metal printing utilizes a metal powder and a print head that applies glue.  This is kind of like SLS only instead of a laser melting the powder, a glue binds it.  You may wonder, what use is a metal product held together by glue?  It’s basically useless because the strength of the product is limited to the weakest material.  Hence the metal prints require a secondary production process– they are embedded in sand and fired in an oven adjacent to a pocket of a second powdered metal.  The heat of the oven burns off the glue and liquifies the second metal which then infuses into the holes left by the glue and creates an all-metal part.  The strength is now limited by the strength of the second metal rather than the strength of an adhesive.

These are by no means the only technologies that fall into the category of 3D printing– new technologies are constantly being developed to print using various materials including foods, starches, waxes, rubbers, plastics, metals, and even human body cells like bone and liver.   An article titled “Source Materials” in the April 2014 issue of Metropolis Magazine (pg. 57-9) mentions a company called Emerging Objects who are experimenting with printing from salt, paper, and wood.  But the possibilities are truly endless, it’s only a matter of developing the technologies to make them work… and the next step appears to be something dubbed “4D printing” which is a topic for another post.

For further information see:

Wikipedia on 3D printing

Watch a video from Shapeways

Interested in trying to print something yourself or buying a printed product?  Try…

Shapeways (printing services)

Ponoko (printing and laser cutting services)

MakerBot (printers)

3D Systems (printers)

Stratasys (printers)

and recently Amazon began carrying printers and printing supplies.


Thoughtful Information for Fearless Individuals