Dartmouth Smart Ink Adds Shape-Changing 4D Printing Power

Author: Dartmouth College
Published: 4 Apr 2018 - Updated: 28 Sep 2026
Publication Type: Announcement

Table of Contents:
Synopsis - Definition - Overview - FAQs - Insights, Updates - Related Content

Synopsis

This research from Dartmouth College describes a smart ink that turns ordinary 3D-printed structures into objects that can change shape and color after printing, a process known as 4D printing. The work was selected as a VIP paper by Angewandte Chemie, the peer-reviewed journal of the German Chemical Society. Its main finding is that printed objects can be shrunk to 1 percent of their original size while gaining 10 times the resolution, which lets a $1,000 printer produce parts that once needed a $100,000 machine. Led by chemistry professor Chenfeng Ke, the team built the ink around a polymer-based carrier that moves functional molecules from the nanoscale up to objects you can see with the naked eye. This matters to materials chemists, 3D printing engineers, and the biomedical and energy fields because it cuts the cost of precision parts sharply. It also points toward printed bone replacements and drug delivery devices, which could one day benefit seniors and people with disabilities who rely on affordable, custom-made medical parts.*

At a Glance

• 1 - The ink prints at a rough 300-micron resolution, yet the finished object shows a much finer 30-micron line width.
• 2 - Supramolecular pillars let printed objects expand and contract repeatedly. Fluorescent trackers make them change color when exposed to light.
• 3 - A series of post-printing reactions locks the active ingredients together. This preserves the molecular structure from the gel stage through the final object.
• 4 - Standard photo-curing resins produce hard plastics with rigid but random molecular architecture. The new method keeps specific molecular alignments and functions intact.

Topic Definition

4D Printing

4D printing is a form of additive manufacturing in which a 3D-printed object is designed to change its shape, size, color, or other properties over time in response to an outside trigger such as heat, light, moisture, or a chemical fuel. The fourth dimension is time. Instead of ending as a fixed shape, the printed part carries programmed behavior in its material structure, often through smart polymers, hydrogels, or molecular systems that react in predictable ways. This lets engineers build self-assembling structures, adaptive medical implants, responsive filters, and parts that fold, expand, or contract on their own after they leave the printer.

Overview

Researchers at Dartmouth College have developed a smart ink that turns 3D-printed structures into objects that can change shape and color. The innovation promises to add even more functionality to 3D printing and could pave the way to a new generation of printed material.

The advancement in the area of form-changing intelligent printing - also known as 4D printing - provides a low-cost alternative to printing precision parts for uses in areas ranging from biomedicine to the energy industry.

"This technique gives life to 3D-printed objects," said Chenfeng Ke, an assistant professor of chemistry at Dartmouth. "While many 3D-printed structures are just shapes that don't reflect the molecular properties of the material, these inks bring functional molecules to the 3D printing world. We can now print smart objects for a variety of uses."

Many 3D printing protocols rely on photo-curing resins and result in hard plastic objects with rigid, but random molecular architectures. The new process allows designers to retain specific molecular alignments and functions in a material and converts those structures for use in 3D printing.

By using a combination of new techniques in the pre-printing and post-printing processes, researchers were able to reduce printed objects to 1 percent of their original sizes and with 10-times the resolution. The 3D printed objects can even be animated to repeatedly expand and contract in size through the use of supramolecular pillars. With fluorescent trackers, the objects can be made to change color in response to an external stimulus such as light.

The ability to reduce the size of an object after printing while preserving functional features and increasing resolution allows inexpensive printers to print high-resolution objects that were once only possible with much more sophisticated printers.

According to the study, which was selected as a VIP paper by Angewandte Chemie, the journal of the German Chemical Society, the smart ink can print at a rough, 300-micron resolution, but the end product would feature a much finer line width of 30 microns.

"This process can use a $1,000 printer to print what used to require a $100,000 printer," said Ke. "This technique is scalable, widely adaptable and can dramatically reduce costs."

To create the smart ink, researchers used a polymer-based "vehicle" that integrates intelligent molecular systems into printing gel and allows for the transformation of their functions from the nanosacle to the macroscale.

While most materials are readily hardened during the 3D printing process, the new process introduces a series of post-printing reactions which lock the active ingredients together and retain the form of the molecular structure throughout the printing process.

The result is a printed object with a molecular design that is programmed to transform itself: If you provide it with chemical fuel, it changes shape. If you shine a light on it, it can change color.

"This is something we've never seen before. Not only can we 3D print objects, we can tell the molecules in those objects to rearrange themselves at a level that is viewable by the naked eye after printing. This development could unleash the great potential for the development of smart materials," Ke said.

While researchers believe the technology is still far away from intelligent 3D systems that can dynamically change their configuration, current uses for the technology could be to print precision filters and storage devices. Over time, researchers expect that the process could result in a new class of macroscale 3D printed objects that can be used to deliver medicine or produce high resolution bone replacements.

According to the research team involved in the study:

"We believe this new approach will initiate the development of small molecule-based 3D printing materials and greatly accelerate the development of smart materials and devices beyond our current grasp that are capable of doing complex tasks in response to environmental stimuli."

In the immediate term, researchers expect the smart inks to be useful to materials chemists, 3D printing engineers and others interested in bringing functional materials into 3D printing.

Frequently Asked Questions

NOTE: Researched FAQs by Disabled World (DW)

What is the difference between 3D printing and 4D printing?

3D printing builds a fixed object layer by layer, while 4D printing creates objects designed to change shape, size, or color over time when exposed to a trigger such as light, heat, water, or a chemical.

What materials are commonly used in 4D printing?

Common 4D printing materials include shape memory polymers, hydrogels, liquid crystal elastomers, and composite inks that contain responsive molecules or fibers.

How could 4D printing help people with disabilities?

4D printing could lead to lower cost custom prosthetic parts, braces that adjust to the body, and implants that expand or reshape inside the body, reducing the need for repeated fittings or surgeries.

Can 4D printed objects be used inside the human body?

Researchers are testing biocompatible 4D printed stents, tissue scaffolds, and drug delivery devices, but most medical uses are still in laboratory or early clinical study stages.

What is a hydrogel in 3D printing?

A hydrogel is a water-rich network of polymer chains that can swell or shrink, making it useful for soft printed structures, tissue engineering, and objects that change size after printing.

Why does shrinking a printed object increase its resolution?

When an object shrinks evenly after printing, all of its features shrink with it, so lines and details that were printed coarsely become much finer in the finished part.

Is 4D printing available to consumers or hobbyists?

Some simple 4D printing effects can be achieved with shape memory filaments on desktop printers, but advanced smart inks and molecular systems remain mostly limited to research labs.

What industries are expected to benefit most from 4D printing?

Healthcare, aerospace, construction, textiles, soft robotics, and energy are expected to benefit most, since they need parts that adapt to changing conditions without extra motors or electronics.

Insights, Analysis, and Developments

Editorial Note: Most 3D printing still turns out objects that are just shapes. The material inside has no real job beyond holding its form. The Dartmouth approach changes that by giving the molecules in a printed object instructions they carry out after printing: add chemical fuel and the object changes shape, shine a light and it changes color. The researchers say intelligent systems that fully reconfigure themselves are still a long way off. Even so, near-term uses such as precision filters and storage devices show the method already works outside the lab bench. The bigger story is access. When a scalable, adaptable technique lets low-cost equipment reach high resolution, custom medical parts and assistive components get closer to the clinics, makerspaces, and small manufacturers that serve people with disabilities, not just well-funded research centers.*

Attribution/Source(s): This quality-reviewed publication was selected for publishing by the editors of Disabled World (DW) due to its relevance to the disability community. Originally authored by Dartmouth College and published on 4 Apr 2018, this content may have been edited for style, clarity, or brevity.

* Editorial additions by Ian C. Langtree.