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Ren et al. Soft Sci. 2026, 6, 6 Page 23 of 33

delivered in compact form, then unfold, bend, or self-assemble into patient-specific geometries. This
enhances defect conformity, suture-free fixation, and early mechanical stability. Subsequently, their
programmed transformations and tunable stiffness profiles provide time-sequenced mechanical and
topographical cues that promote cell polarization, collective migration, extracellular matrix deposition,
vascular ingrowth, and maturation .
[144]

Lin et al. demonstrated biodegradable and patient-specific shape-memory occlusion devices for cardiac
defect repair, incorporating Fe O into a PLA matrix for remote magnetic deployment after implantation .
[145]
3
4
The devices supported cell adhesion and ingrowth that promoted rapid endothelialization and offered a
degradable alternative to metal occluders [Figure 8D]. Moving from cardiovascular repair to neural
regeneration, Miao et al. created a multi-responsive architecture by SLA, employing stress-induced
transformation and solvent relaxation to realize reprogrammable shape changes [146] . Graphene-hybridized
nerve guidance conduit provided physical guidance, chemical cues, dynamic self-entubulation, and seamless
integration to support nerve repair [Figure 8E]. Extending the concept to osteogenesis, You et al. fabricated a
bilayer morphing membrane that combined a SMP layer and a hydrogel layer to regulate microstructure and
macroscopic geometry in vivo [147] . By precisely timing the transition between stem cell proliferation and
differentiation states while non-invasively conforming to defect contours, the membrane achieved over 30%
greater new bone formation compared to static controls [Figure 8F]. In parallel, 4D bioprinting has enabled
self-forming vascular architectures that can provide perfusable, conformal conduits for vascular tissue
engineering, offering a complementary pathway for building functional tissue interfaces in situ .
[148]
Stent
The 4D-printed soft stents extend patient-customized 3D stents by incorporating programmable morphing
and active dynamic properties. This stent achieves catheter-level compression for non-invasive delivery and
on-demand expansion in response to clinically compatible signals such as body temperature, magnetic or
photothermal heating, pH/ionic changes, or ultrasound. This capability allows it to resist displacement and
adapt to peristalsis, maintaining lumen patency while minimizing epithelial damage . Target sites span the
[149]
airway, esophagus, blood vessels, ureter, and biliary ducts.

Maity et al. 3D-printed shape-memory tracheal stents using flexible photopolymerizable polypropylene
glycol and polycaprolactone inks and implemented an in-situ welding strategy of thin layers to reduce the
insertion profile and increase flexibility [150] . Porous architectures reduced mucus plugging, polypropylene
glycol-modified surfaces and ciprofloxacin loading provided anti-biofilm and antibacterial functions. In vitro
assays supported cytocompatibility and anti-adhesion properties [Figure 8G]. To address temporal control
for implant deployment, Ni et al. developed a 4D printable phase-separating shape memory hydrogel that
changed shape at ambient or body temperature with a programmable delay in recovery onset . This
[15]
naturally triggered yet actively controllable behavior supported stent concepts that required precise
scheduling without external hardware [Figure 8H]. Extending toward gastrointestinal applications, Lin et al.
created shape memory biocomposites triggered near body temperature and printed biodegradable
biomimetic intestinal stents with tunable transition temperature [151] . The wavy network designs matched
nonlinear tissue mechanics to minimize wall irritation, and biodegradability avoided the secondary
endoscopic removal [Figure 8I].

Sensing
In 4D-printed soft microrobots, the integrated paradigm where the body itself functions as a sensor is
replacing the traditional approach of constructing the structure first and then attaching sensors. Through
multi-material co-printing, load-bearing skeletons, actuation, and sensing are synergistically designed and
formed within the same configuration, thereby transforming deformation itself into readable signals .
[152]