4D printing

In plain language

A normal 3D printer makes an object that stays the same shape once it is finished. 4D printing adds time to the picture: the printed part is made from a smart material that is designed to change shape later, often when it is warmed, wetted or placed in a magnetic field. A flat printed sheet might fold into a box, or a compressed tube might open out into a larger one.

Most of the demonstrations so far are small, laboratory-scale objects. Their shape change can be fast or slow, and it often depends on the temperature or water content of the surroundings. Researchers are testing whether the same idea can produce medical devices, such as stents that open inside a blood vessel, but these are still at an early stage.

Technical explanation

The most developed route uses shape-memory polymers. The part is printed in a shape, then deformed while warm, cooled to lock in a temporary shape, and reheated above its glass transition temperature (Tg) so that it returns to the printed shape. Ge and colleagues (2016) printed multimaterial shape-memory structures using projection microstereolithography with photocurable methacrylate-based polymer networks, reporting features down to a few microns and a maximum stretchability of about 330% at 40 °C for one formulation. Their results show that the process is sensitive to temperature: shape fixity was above 90% when the part was programmed at or near Tg, and fell sharply when programmed 20 °C below it. Recovery was also slow at low temperature, with about 10% recovery after 20 minutes at 35 °C, against full recovery of a printed spring within 3 minutes at 60 °C.

Other triggers use different mechanisms. Gladman and colleagues (2016) printed 3D hydrogel composites in which aligned cellulose fibrils set the anisotropic swelling, so the material changes shape when immersed in water. Kim and colleagues (2018) used a magnetic field during printing to align magnetic particles and so program ferromagnetic domains into soft materials; the printed structures change shape quickly under remote magnetic control. Raviv and colleagues (2014) described a method for simulating and fabricating printed structures that change shape after printing, in response to their environment.

For medical use, Li and colleagues (2026) printed vascular stents from a polycaprolactone-based shape-memory composite by projection micro-stereolithography. Adding diethyl phthalate as a plasticizer brought the thermal transition to about 37 °C, so the stents recover shape at body temperature. The reported testing covers in vitro cytocompatibility, finite element modelling and implantation in mice. No clinical use is reported.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Limitations and open problems

• Recovery can be slow at low temperatures. Ge and colleagues (2016) report about 10% recovery after 20 minutes at 35 °C, while full recovery of a printed spring took within 3 minutes at 60 °C.
• Shape fixity depends on the programming temperature. Ge and colleagues (2016) report fixity above 90% near the glass transition temperature and a sharp drop when programmed 20 °C below it.
• Medical work is preclinical. The 2026 vascular stent study reports in vitro cytocompatibility tests and implantation in mice, and no clinical use is reported.
• Long-term durability is not established. The sources reviewed for this profile do not report fatigue performance over many repeated shape changes for printed 4D structures.
• Some routes need special inks or set-ups. The magnetic route needs ferromagnetic particles in the soft material and an external field, and the hydrogel route needs fibre alignment during printing (Kim and colleagues, 2018; Gladman and colleagues, 2016).
• Build size, throughput and cost are not quantified in the sources reviewed here, so practical scale-up cannot be judged from them.

Possible future uses

Timeline

1. 18 Dec 2014Raviv and colleagues publish active printed materials for complex self-evolving deformations in Scientific Reports, describing structures that change shape after printing in response to their environment. Sources: [4]
2. 25 Jan 2016Gladman and colleagues publish biomimetic 4D printing of hydrogel composites that change shape in water, online in Nature Materials. Sources: [2]
3. 8 Aug 2016Ge and colleagues publish multimaterial 4D printing with tailorable shape-memory polymers in Scientific Reports, with maximum stretchability and recovery conditions reported. Sources: [1]
4. 13 Jun 2018Kim and colleagues publish printed ferromagnetic domains for untethered, fast-transforming soft materials in Nature. Sources: [3]
5. 15 Jan 2026Li and colleagues publish adaptive 4D-printed vascular stents that recover at body temperature, tested in vitro and in mice, in Advanced Functional Materials. Sources: [5]

Futures this could help bring about

How far away?

Medical implants that change shape inside the body

Pilots · 3 of 5 steps done

Glossary

Shape-memory polymer

A polymer that can be deformed, hold a temporary shape, and return to its original shape when triggered, usually by heat.

Glass transition temperature (Tg)

The temperature at which a polymer changes from a stiff, glassy state to a softer, rubbery state. Shape-memory polymers are usually programmed and recovered around this point.

Shape fixity

How well a material holds a temporary shape after it has been deformed and cooled.

Direct ink writing

A printing method that extrudes a viscous ink through a nozzle, layer by layer, to build a three-dimensional part.

Sources

1. peer reviewed paper
   Multimaterial 4D Printing with Tailorable Shape Memory Polymers
   Qi Ge, Amir Hosein Sakhaei, Howon Lee et al.. Scientific Reports, 8 Aug 2016. DOI: 10.1038/srep31110. Accessed 22 Oct 2026.
2. peer reviewed paper
   Biomimetic 4D printing
   A. Sydney Gladman, Elisabetta A. Matsumoto, Ralph G. Nuzzo et al.. Nature Materials, 25 Jan 2016. DOI: 10.1038/nmat4544. Accessed 22 Oct 2026.
3. peer reviewed paper
   Printing ferromagnetic domains for untethered fast-transforming soft materials
   Yoonho Kim, Hyunwoo Yuk, Ruike Zhao et al.. Nature, 13 Jun 2018. DOI: 10.1038/s41586-018-0185-0. Accessed 22 Oct 2026.
4. peer reviewed papercorrected
   Active Printed Materials for Complex Self-Evolving Deformations
   Dan Raviv, Wei Zhao, Carrie McKnelly et al.. Scientific Reports, 18 Dec 2014. DOI: 10.1038/srep07422. Accessed 22 Oct 2026.
5. peer reviewed paper
   Adaptive 4D-Printed Vascular Stents With Low-Temperature-Activated and Intelligent Deployment
   Yannan Li, Yifan Pan, Chikahiro Imashiro et al.. Advanced Functional Materials, 15 Jan 2026. DOI: 10.1002/adfm.202521468. Accessed 22 Oct 2026.

Revision history

3 changes since this profile was created.