Botanical systems have evolved the intriguing ability to respond to diverse stimuli due to long‐term survival competition. Mimicking these dynamic behaviors has greatly advanced the developments in wide fields ranging from soft robotics, precision sensors to drug delivery and biomedical devices. However, realization of stimuli‐responsive components at the microscale with high response speed still remains a significant challenge. Herein, the miniature biomimetic 4D printing of pH‐responsive hydrogel is reported in spatiotemporal domain by femtosecond laser direct writing. The dimension of the printed architectures is at the microscale (<102 µm) and the response speed is reduced down to subsecond level (<500 ms). Shape transformation with multiple degrees of freedom is accomplished by taking advantage of pH‐triggered expansion, contraction, and torsion. Biomimetic complex shape‐morphing is enabled by adopting flexible scanning strategies. In addition, application of this 4D‐printed micro‐architecture in selective micro‐object trapping and releasing is demonstrated, showcasing its possibilities in micromanipulation, single‐cell analysis, and drug delivery.

Expression of rRNA affects cell growth and proliferation, but mechanisms that modulate rRNA levels are poorly understood. We conducted a genetic screen for factors that negatively regulate generation of endogenous short interfering RNA (endo-siRNA) in Caenorhabditis elegans and identified a suppressor of siRNA (susi-1) and antisense ribosomal siRNAs (risiRNAs). risiRNAs show sequence complementary to 18S and 26S rRNAs and require RNA-dependent RNA polymerases (RdRPs) for their production. They act through the nuclear RNA interference (RNAi) pathway to downregulate pre-rRNA. Stress stimuli, including low temperature and UV irradiation, induced the accumulation of risiRNAs. SUSI-1 is a homolog of the human DIS3L2 exonuclease involved in 3'-5' degradation of oligouridylated RNAs. In susi-1 mutant and in low temperature-treated animals, 3'-tail oligouridylated 26S rRNA accumulated. The injection of oligouridylated rRNA elicited nuclear accumulation of NRDE-3. Our findings identify a new subset of 22G-RNAs that regulate pre-rRNA expression and a mechanism to maintain rRNA homeostasis.

Microrobots have attracted considerable attention due to their extensive applications in microobject manipulation and targeted drug delivery. To realize more complex micro-/nanocargo manipulation (e.g., encapsulation and release) in biological applications, it is highly desirable to endow microrobots with a shape-morphing adaptation to dynamic environments. Here, environmentally adaptive shape-morphing microrobots (SMMRs) have been developed by programmatically encoding different expansion rates in a pH-responsive hydrogel. Due to a combination with magnetic propulsion, a shape-morphing microcrab (SMMC) is able to perform targeted microparticle delivery, including gripping, transporting, and releasing by “opening–closing” of a claw. As a proof-of-concept demonstration, a shape-morphing microfish (SMMF) is designed to encapsulate a drug (doxorubicin (DOX)) by closing its mouth in phosphate-buffered saline (PBS, pH ∼ 7.4) and release the drug by opening its mouth in a slightly acidic solution (pH < 7). Furthermore, localized HeLa cell treatment in an artificial vascular network is realized by “opening–closing” of the SMMF mouth. With the continuous optimization of size, motion control, and imaging technology, these magnetic SMMRs will provide ideal platforms for complex microcargo operations and on-demand drug release.

Inspired by flagellate microorganisms in nature, the microhelix is considered as an ideal model for transportation in fluid environment with low Reynolds number. However, how to promote the swimming and loading capabilities of microhelices with controllable geometries remains challenging. In this study, a novel kind of conical hollow microhelices is proposed and a method is developed to rapidly fabricate these microhelices with controllable parameters by femtosecond vortex beams generated from spatial light modulation along helical scanning. Conical hollow microhelices with designable heights (H = 45–75 µm), diameters (D = 6–18 µm), pitch numbers (Pi = 2–4), taper angles (T = 0.1–0.6 rad), and pitch periods (ΔP = 10–30 µm) are efficiently fabricated. In addition, compared with straight microhelices, the forward swimming capability of conical microhelices increases by 50% and the lateral drift of the conical hollow microhelices is reduced by 70%. Finally, the capabilities of these conical hollow microhelices for nanocargo loading and release by the inner hollow core, as well as transportation of neural stem cells by the outer surface are demonstrated. This work provides new insights into faster and simultaneous transportation of multicargoes for hybrid drug delivery, targeted therapy, and noninvasive surgery in vivo.