The study asks how light-based additive manufacturing can produce hydrogel structures with controlled material interfaces, chemical gradients and stiffness. Experiments demonstrate multimaterial GelMA and four-arm polyethylene glycol structures using resin exchange, two-photon-printed honeycombs, reversible rhodamine B loading and retained acrylated-dye gradients, alongside tunable mechanical properties and a salt-responsive capacitance demonstration. The diffusion coefficient is an effective macroscopic estimate from optical images; biocompatibility was assessed only preliminarily in a 24-hou

Materials Advances · 2026

Print a hydrogel with light. Then choose where molecules go—and whether they stay.

A study in shaping water-rich materials, from two-photon-printed honeycombs to chemical gradients that survive a rinse.

Keyvan Joderi and colleagues Materials Advances 7, 6020–6028

01 / The molecular experiment

Will the colour stay?

Both dyes enter the printed gel. One carries an acrylate group that can join the network. Load them, then add fresh water.

At 1 h, the ordinary-dye teaching model reaches 2.3 mm . Both gradients are still loading.

The same shape. A different molecular fate.

GelMA—gelatin methacryloyl—is a gelatin-derived material that forms a water-filled network when crosslinked by light. Small molecules can move through that network.

Ordinary rhodamine B diffuses back into water during washing. Acrylated rhodamine B can react with residual methacrylate groups, leaving a retained colour gradient. The paper observes this contrast after a 14-hour rinse.

The paper used 20% GelMA cuboids, 5 × 5 × 10 mm, loaded from below with 1 mg mL⁻¹ dye. Images show approximately 8 mm of ordinary-dye penetration and 5 mm of acrylated-dye penetration after 14 h.

The ordinary-dye scene uses L = √(2Dt), with the paper’s effective macroscopic D = 7.5 × 10⁻⁶ cm² s⁻¹. This gives 8.7 mm at 14 h. The acrylated-dye rise and the two-second rinse animation are qualitative illustrations. The rinse compresses 14 h in water into a short visual transition.

02 / The fabrication experiment

Write the architecture with light.

Light crosslinks the material where the structure should be. Compare a focused two-photon writing beam with projected light, then explore what exposure changes.

Choose a printing route

Two-photon polymerization localizes crosslinking around a focused beam. The researchers used an UpNano NanoOne printer to form sharply defined honeycomb walls.

Measured two-photon honeycomb. Overall structure: 1 × 1 × 0.3 mm.

Bottom-up printing used a 10× objective (NA 0.4), at approximately 28 °C, with 1 µm layer and hatch spacing. The methods report screening laser powers of 25–300 mW and scan speeds of 100–800 mm s⁻¹. These ranges describe the fabrication screening experiment.

The projection-printed honeycomb had walls of 20 ± 3 µm and cavities of 85 ± 2 µm. The two routes used different designs. The three-dimensional applet illustrates the printing mechanisms and the projection cavity trend.

03 / Beyond one material

A sharp boundary. Or a smooth gradient.

The study offers two ways to put different chemistry into one structure. One strategy creates a defined interface; the other creates a continuous transition.

Change the resin.

Print part of the structure, exchange the resin vat, then continue. Cross-polymerization connects the boundary. The paper combines GelMA with GelMA or four-arm PEG acrylate, retaining distinct chemical regions after washing.

Let molecules diffuse.

Load molecules from one side of an already printed gel. Diffusion produces a continuous gradient; reactive guest molecules can make that gradient persist through a water rinse.

Another dial: stiffness

Exposure also changes the network.

For four-arm PEG acrylate, the reported Young’s modulus rose with exposure and an additional light cure.

14 mW/cm²

28 mW/cm²

With 60 s postcure

04 / The response experiment

A gel can be a sensing interface.

Put a printed hydrogel over interdigitated graphene/PEDOT:PSS electrodes. Ions exchange with the hydrated gel, changing the measured capacitance.

Hydrogel-covered electrodes · 0 M NaCl

Each choice displays a reported measurement. Moving ions illustrate exchange; their trajectories are schematic.

Printed gelatin-based hydrogel sensing demonstration · Figure 6, Joderi et al. (2026).

05 / From the paper

Look at the evidence.

The original microscopy and photographs connect the experiments above to the structures and gradients the researchers actually made.

Architecture follows exposure.

Panels c and d compare projection-printed and two-photon-printed honeycombs. Panel b shows cavities narrowing as projection intensity increases.

Chemical regions survive washing.

Resin exchange creates distinct regions in blocks and a porous lattice. Acrylated dye reveals the retained composition after water washing.

A molecular handle changes the outcome.

Rhodamine B leaves the gel during washing. The acrylated dye retains a gradient. The plotted diffusion lengths quantify their different rise.

Figures 2, 4 and 5 reproduced as supplied crops; content within the crops is unchanged. © 2026 The Author(s), published by the Royal Society of Chemistry, CC BY 4.0.

What this opens up

Shape is only the beginning.

Position material functions.

Place chemical or mechanical regions within one connected printed structure.

Load after making.

Separate the fabrication of a shape from the later introduction of molecular gradients.

Connect soft matter to electronics.

Use hydrated gels as interfaces for ion-responsive printed devices.

These design strategies point toward scaffolds with spatial cues, molecular delivery systems and soft sensing devices. The dyes serve as model guest molecules in this study.

The research

Multimaterial additive manufacturing of GelMA hydrogel-based structures with tuneable composition and mechanical properties

Keyvan Joderi, Silvia Santoni, Charles E. D. Heaton, Feiran Wang, Nathan Carpentier, Long Jiang, Felicity R. A. J. Rose, Ricky D. Wildman and Lyudmila Turyanska

Materials Advances 7, 6020–6028 (2026) · DOI: 10.1039/d6ma00041j ↗

An interactive companion to the research.

Original research and reproduced figures: © 2026 The Author(s), Royal Society of Chemistry. CC BY 4.0.

The graphical abstract is an AI-generated conceptual illustration. Interactive scenes are explanatory adaptations; model assumptions are noted beside the experiments.

Joderi et al., Materials Advances (2026) · reproduced crop · CC BY 4.0