Abstract
Stimulus-responsive shape-shifting polymers1,2,3 have shown unique promise in emerging applications, including soft robotics4,5,6,7, medical devices8, aerospace structures9 and flexible electronics10. Their externally triggered shape-shifting behaviour offers on-demand controllability essential for many device applications. Ironically, accessing external triggers (for example, heating or light) under realistic scenarios has become the greatest bottleneck in demanding applications such as implantable medical devices8. Certain shape-shifting polymers rely on naturally present stimuli (for example, human body temperature for implantable devices)8 as triggers. Although they forgo the need for external stimulation, the ability to control recovery onset is also lost. Naturally triggered, yet actively controllable, shape-shifting behaviour is highly desirable but these two attributes are conflicting. Here we achieved this goal with a four-dimensional printable shape memory hydrogel that operates via phase separation, with its shape-shifting kinetics dominated by internal mass diffusion rather than by heat transport used for common shape memory polymers8,9,10,11. This hydrogel can undergo shape transformation at natural ambient temperature, critically with a recovery onset delay. This delay is programmable by altering the degree of phase separation during device programming, which offers a unique mechanism for shape-shifting control. Our naturally triggered shape memory polymer with a tunable recovery onset markedly lowers the barrier for device implementation.
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All relevant data are available from the corresponding authors on reasonable request. Source data are provided with this paper.
References
Roy, D., Cambre, J. N. & Sumerlin, B. S. Future perspectives and recent advances in stimuli-responsive materials. Prog. Polym. Sci. 35, 278–301 (2010).
Li, Z. et al. Bioinspired simultaneous changes in fluorescence color, brightness, and shape of hydrogels enabled by AIEgens. Adv. Mater. 32, 1906493 (2020).
Palleau, E., Morales, D., Dickey, M. D. & Velev, O. D. Reversible patterning and actuation of hydrogels by electrically assisted ionoprinting. Nat. Commun. 4, 2257 (2013).
Gelebart, A. H. et al. Making waves in a photoactive polymer film. Nature 546, 632–636 (2017).
Ware, T. H., Mcconney, M. E., Wie, J. J., Tondiglia, V. P. & White, T. J. Voxelated liquid crystal elastomers. Science 347, 982–984 (2015).
Kim, Y., Yuk, H., Zhao, R., Chester, S. A. & Zhao, X. Printing ferromagnetic domains for untethered fast-transforming soft materials. Nature 558, 274–279 (2018).
Kim, S. et al. Broadband and pixelated camouflage by exploiting large Poisson effect in main-chain chiral nematic liquid crystalline elastomers. Nat. Mater. 21, 41–46 (2022).
Lendlein, A., Behl, M., Hiebl, B. & Wischke, C. Shape-memory polymers as a technology platform for biomedical applications. Expert Rev. Med. Devices 7, 357–379 (2010).
Li, F., Liu, Y. & Leng, J. Progress of shape memory polymers and their composites in aerospace applications. Smart Mater. Struct. 28, 103003 (2019).
Park, J. K. et al. Remotely triggered assembly of 3D mesostructures through shape-memory effects. Adv. Mater. 31, 1905715 (2019).
Koerner, H., Price, G., Pearce, N. A., Alexander, M. & Vaia, R. A. Remotely actuated polymer nanocomposites-stress-recovery of carbon-nanotube-filled thermoplastic elastomers. Nat. Mater. 3, 115–120 (2004).
Hu, X. et al. Programming temporal shapeshifting. Nat. Commun. 7, 12919 (2016).
Peng, W., Zhang, G., Zhao, Q. & Xie, T. Autonomous off-equilibrium morphing pathways of a supramolecular shape-memory polymer. Adv. Mater. 33, 2102473 (2021).
Zhang, X. et al. Rapid, localized, and athermal shape memory performance triggered by photoswitchable glass transition temperature. ACS Appl. Mater. Interfaces 11, 46212–46218 (2019).
Huang, W., Yang, B., An, L., Li, C. & Chan, Y. Water-driven programmable polyurethane shape memory polymer: demonstration and mechanism. Appl. Phys. Lett. 86, 114105 (2005).
Balk, M., Behl, M., Nöchel, U. & Lendlein, A. Enzymatically triggered jack-in-the-box-like hydrogels. ACS Appl. Mater. Interfaces 13, 8095–8101 (2021).
Xie, T. Tunable polymer multi-shape memory effect. Nature 464, 267–279 (2010).
Liu, Y., Shaw, B., Dickey, M. D. & Genzer, J. Sequential self-folding of polymer sheets. Sci. Adv. 3, e1602417 (2017).
Yuan, J. et al. Shape memory nanocomposite fibers for untethered high-energy microengines. Science 365, 155–158 (2019).
Nonoyama, T. et al. Instant thermal switching from soft hydrogel to rigid plastics inspired by thermophile proteins. Adv. Mater. 32, 1905878 (2020).
Le, X. et al. Stretchable supramolecular hydrogels with triple shape memory effect. Chem. Sci. 7, 6715–6720 (2016).
Guo, W. et al. pH-stimulated DNA hydrogels exhibiting shape-memory properties. Adv. Funct. Mater. 27, 73–78 (2015).
Neffe, A. et al. One step creation of multifunctional 3D architectured hydrogels inducing bone regeneration. Adv. Mater. 27, 1738–1744 (2015).
Miyamae, K., Nakahata, M., Takashima, Y. & Harada, A. Self-healing, expansion-contraction, and shape-memory properties of a preorganized supramolecular hydrogel through host-guest interactions. Angew. Chem. Int. Ed. Engl. 54, 8984–8987 (2015).
Nan, W., Wang, W., Gao, H. & Liu, W. Fabrication of a shape memory hydrogel based on imidazole-zinc ion coordination for potential cell-encapsulating tubular scaffold application. Soft Matter 9, 132–137 (2013).
You, J. et al. Quaternized chitosan/poly(acrylic acid) polyelectrolyte complex hydrogels with tough, self-recovery, and tunable mechanical properties. Macromolecules 49, 1049–1059 (2016).
Wu, J. et al. Rapid digital light 3D printing enabled by a soft and deformable hydrogel separation interface. Nat. Commun. 12, 6070 (2021).
Ding, Z. et al. Direct 4D printing via active composite materials. Sci. Adv. 3, e160289 (2017).
Zarek, M. et al. 3D printing of shape memory polymers for flexible electronic devices. Adv. Mater. 28, 4449–4454 (2016).
Acknowledgements
We thank the National Natural Science Foundation of China (nos. 52033009, 52273112, U20A6001, 22275159 and 22105167) for supporting this work. We thank L. Xu and N. Zheng for their assistance in performing DSC and SEM analyses at the State Key Laboratory of Chemical Engineering (Zhejiang University). We also thank L. Xi (Department of Chemical Engineering, McMaster University) for discussion on the impact of diffusion on recovery behaviour. The digital printing files for the bowl and hyperboloid in Fig. 4a and for the stent in Fig. 4c were downloaded from Thingiverse.com. The digital file for the orbit vase in Fig. 4a,b was created by S. Abrahamsson/Clockspring3D and downloaded from www.myminifactory.com.
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Contributions
T.X., Q.Z. and C.N. conceived the concept and wrote the paper. C.N. and D.C. conducted the majority of the experiments with assistance from X.W., G.C., C.Y., X.C., S.D. and Z.S. MRI characterization was proposed and conducted by Y.Y. and Xueqian Kong. The Kelvin–Voigt model was proposed by R.X. and Q.Z. Potential device applications were discussed, with contributions from J.W., Y.J., C.W., N.W., J.L., Xiangxing Kong, X.J. and Y.S. All authors discussed the results.
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Extended data figures and tables
Extended Data Fig. 1 Mechanical properties and swelling behaviors of the hydrogels.
a, The strain-stress curves of hydrogel samples with different BIS contents, measured at a strain rate of 5 mm/min at 25 °C. b, The Young’s modulus and breaking strain of hydrogel samples with different BIS contents calculated from five parallel experiments. Error bars correspond to s.d. (n = 5). c, Stress-strain curves of the hydrogel with 0.25% of BIS crosslinker at two different temperatures.
Extended Data Fig. 2 Swelling ratio of the hydrogels at different temperatures.
The error bars were obtained from three measured samples with standard deviations.
Extended Data Fig. 3 Shape fixation kinetics at 90 °C water.
The material at 90 °C was held under an external deformation force for a given fixing time. Afterwards, the deformation force was removed and the shape fixation ratio was calculated.
Extended Data Fig. 4 Programmed recovery delay for poly(N-isopropyl acrylamide) hydrogel.
a, Precursors of the poly(N-isopropyl acrylamide) hydrogel and the comparison of its shape recovery kinetics of with and without programming (the photo-images shows a recovery onset of around 2 min). b, Recovery kinetics for poly(N-isopropyl acrylamide) hydrogels prepared with different crosslinker concentrations. The water contents during recovery are 81.9%, 71.7%, 64.6% and 48.4% corresponding to the samples with crosslinker contents of 2.5%, 5%, 7.5% and 10%, respectively. The programming condition is 30 min in the decane. c, Impact of crosslinker concentration on the onset period at a fixed programming time of 30 min. Error bars correspond to s.d. (n = 4). d, Effect of programming time on the recovery kinetics for poly(N-isopropyl acrylamide) hydrogel at a fixed crosslinker concentration of 5.0%. The water contents during recovery are 76.2%, 69.5%, 68.9%, and 64.5% when programming for 10 min, 30 min, 60 min, and 120 min, respectively. e, Impact of programming time on the onset period, corresponding to d. Error bars correspond to s.d. (n = 4). f, Recovery process with an onset period of 10 min after programming for 30 min.
Extended Data Fig. 5 Adjusting the shape recovery behaviors of the hydrogel by altering programming times.
a, The recovery onset with different programming time. Error bars correspond to s.d. (n = 3). b, Shape recovery profiles of the hydrogel with different programming times.
Extended Data Fig. 6 Shape recovery kinetics of hydrogels with different BIS content.
a, Swelling ratio of the hydrogels with different BIS contents. Error bars correspond to s.d. (n = 6). b, DSC curves of the hydrogels with different crosslinking densities. c, Shape recovery kinetics of the hydrogels with various crosslinking densities under an identical programming condition (90 °C, 180 min). d, Onset periods of the hydrogels. Error bars correspond to s.d. (n = 3).
Extended Data Fig. 7 The evidences of internal water redistribution mechanism.
a, The swelling ratio during shape recovery. b, Comparison of the shape recovery in water and oil at 25 °C. c, The shape recovery of the hydrogel samples of different thicknesses in 25 °C water.
Extended Data Fig. 8 The programmed delay recovery of foam composite.
a, DSC curve of the thermo-responsive SMP matrix. b, Comparison of the recovery behaviours of the foam composite with and without delay. The foam composite was programmed at 40 °C and 90 °C for 10 min respectively, followed by heating at 40 °C to trigger its recovery. c, Photos demonstrating no recovery delay when the sample was programmed at 40 °C, whereas an obvious delay of 5 min was observed when the sample was programmed at 90 °C for 10 min.
Supplementary information
Supplementary Information
The supplementary information includes Supplementary Notes 1–7, Figs. 1–13, Table 1 and references.
Supplementary Video 1
Delayed shape recovery of a hydrogel windmill.
Supplementary Video 2
Delayed recovery of a poly(N-isopropylacrylamide) hydrogel.
Supplementary Video 3
Heat-triggered recovery process of a SMP composite with no onset delay.
Supplementary Video 4
Heat-triggered shape recovery process of a SMP composite with an onset delay.
Supplementary Video 5
Comparison of deployment behaviours between two SMP stents with and without recovery onset delay.
Supplementary Video 6
Comparison of an identical SMP probe with and without a programmed delay.
Supplementary Video 7
Sequential recovery process of an SMP with regionally distinct onset delays.
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Ni, C., Chen, D., Yin, Y. et al. Shape memory polymer with programmable recovery onset. Nature 622, 748–753 (2023). https://doi.org/10.1038/s41586-023-06520-8
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DOI: https://doi.org/10.1038/s41586-023-06520-8
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