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Page 26 of 33 Ren et al. Soft Sci. 2026, 6, 6

with favorable safety, yet tracking can be affected by speckle and limited visibility near gas/bone interfaces,
and robust 3D state estimation often requires multi-view acquisition or advanced reconstruction [163,164] ;
optical coherence tomography (OCT) offers micrometer-scale resolution and fast imaging for precise state
observation but is restricted to shallow depths and optically accessible scenarios [165,166] ; and X-ray provides
deep penetration and high frame rates with established clinical workflows but faces radiation burden, limited
soft-tissue contrast, and 2D projection ambiguity [167,168] . Simulation models still fall short in capturing real-
time dynamic responses and multi-physics coupling, while cross-laboratory reproducibility and ethical
compliance remain underdeveloped.

To further advance the development of 4D-printed soft microrobots, it is recommended to pursue four
coordinated fronts: standards, models, data, and systems. Establish consistent evaluation and safety
specifications, along with benchmark datasets and open workflows for materials and processes. Integrate
machine learning and digital twins into end-to-end inverse design and process control to enable in-situ
monitoring and closed-loop self-calibration. Develop high-force-density materials triggered near body
temperature with low-loss field coupling, and pursue hybrid multi-field actuation with on-demand
reprogramming. On system integration, prioritize multi-material strategies for wireless power and readout,
and validate them in combination with minimally invasive delivery, image-guided navigation, and
pharmacological safety. A staged pathway from benchtop to small- and then large-animal studies should be
planned early.

The technique 4D printing introduces time as a design degree of freedom for soft microrobots, enabling
adaptive, self-assembling, and reconfigurable functionality. With coordinated progress in programmable
materials, precise manufacturing, intelligent design tools, and standardization, the field is poised to transition
from proof-of-concept prototypes to reproducible, regulatable clinical and industrial applications. Achieving
usable, controllable, and trustworthy shape-morphing will hinge on deep collaboration among materials
scientists, manufacturing engineers, clinicians, and ethicists.

DECLARATIONS
Authors’ contributions
Conceptualization, research, and manuscript writing: Ren, Z.
Manuscript review and revision: Xie, H.; Fan, X.; Sun, M.
Supervision, project administration, funding acquisition: Fan, X.; Sun, M.
All authors have read and approved the final version of the manuscript.

Availability of data and materials
Not applicable.

Financial support and sponsorship
This work was supported in part by the National Key R&D Program of China under Grant 2023YFB4705600,
and in part by the National Natural Science Foundation of China under Grant 61925304 (Xie, H.).
Additional support was provided by the National University of Singapore Start-up Grant (WBS: A-0010108-
00-00 and A-0010108-01-00) and the National Natural Science Foundation of China under Grant 62422313
(Fan, X.).

Conflicts of interest
All authors declared that there are no conflicts of interest.

Ethical approval and consent to participate
Not applicable.

Consent for publication
Not applicable.

Copyright
© The Author(s) 2026.