Necklace-Like Microfibers with Variable Knots and Perfusable Channels Fabricated by an Oil-Free Microfluidic Spinning Process

High pairing rate Janus-structured microfibers and array: high-efficiency conjugate electrospinning fabrication, structure analysis and co-instantaneous multifunctionality of anisotropic conduction, magnetism and enhanced red fluorescence

A highly efficient and convenient conjugate electrospinning technique is employed to obtain high pairing rate Janus-structured microfibers in electrospun products by optimizing the spinning conditions. In addition, a Janus-structured microfiber array rendering tri-functional performance of tunable magnetism, electrically anisotropic conduction and increased fluorescence is prepared via the same technique using a rotating device as a fiber collector. The array is composed of an ordered arrangement of Janus-structured microfibers. The extraordinary Janus structure and oriented arrangement endow the Janus-structured microfibers with excellent fluorescence. The fluorescence intensity of the Janus-structured microfiber array is, respectively, 1.21, 14.3 and 20.3 times higher than that of the Janus-structured microfiber non-array, the composite microfiber array and the composite microfiber non-array. The Janus-structured microfiber array has a similar saturation magnetization to the contradistinctive specimens. Additionally, the magnetism of the Janus-structured microfiber array can be modulated with different mass ratios of Fe₃O₄ nanoparticles (NPs), and the conductance ratio between the length direction and diameter direction of the Janus-structured microfibers for the array can be tuned from 10³ to 10⁶ by adding a higher percentage of polyaniline (PANI). Our new findings have established a highly efficient conjugate electrospinning technique to prepare Janus-structured microfibers of high pairing rate, and complete isolation of fluorescent material from magnetic nanoparticles and conductive material is accomplished in the Janus-structured microfibers to ensure high fluorescence intensity without a notably disadvantageous influence of dark-colored substances. More importantly, the fabrication technique for the Janus-structured microfibers can be generalized to manufacture other Janus-structured multifunctional materials.

High pairing rate Janus-structured microfibers and their arrays, rendering simultaneous anisotropic conduction, magnetism and fluorescence, are successfully fabricated via conjugate electrospinning.

Electric Field-Induced Cutting of Hydrogel Microfibers with Precise Length Control for Micromotors and Building Blocks

Microfiber modules with controllable lengths emerged as novel biomimetic platforms and are significant for many tissue engineering applications. However, accurately controlling the length of microfibers on the scale of millimeter or even micrometer still remains challenging. Here, a novel and scalable strategy to generate microfiber modules with precisely tunable lengths ranging from 100 to 3500 μm via an alternating current (AC) electric field is presented. To control the microfiber length, double-emulsion droplets containing a chelating agent (sodium citrate) as a spacing node are first uniformly embedded in the microfibers in a controllable spatial arrangement. This process is precisely tuned by adjusting the flow rates, thus, tailoring the resulting multicompartmental microfiber structure. Next, an AC voltage signal is used to trigger the electric field-induced cutting process, where the time-averaged electrical force acting on the induced bipolar charge from the Maxwell-Wagner structural polarization mechanism breaks the stress balance at the interfaces, rupturing the double-emulsion droplets, and resulting in the burst release of the encapsulated chelating agents into the hydrogel cavity. The outer hydrogel shell is quickly dissolved by a chemical reaction, cutting the long fiber into a series of microfiber units of given length. Furthermore, adding magnetic nanoparticles endows magnetic functionality with these microfiber modules, which are allowed to serve as micromotors and building blocks. This electro-induced cutting method provides a facile strategy for the fabrication of microfibers with desired lengths, showing considerable promise for various chemical and biological applications.

Dehydration-triggered shape morphing based on asymmetric bubble hydrogel microfibers

Inspired by nature, scientists have been engaged in developing deformable artificial systems. Here, we propose an innovative method to realize controllable deformations using asymmetric bubble hydrogel microfibers produced by microfluidic cascaded coaxial devices. Asymmetric geometries, coupled with the mismatched shrinkage ratio, contribute to deformations upon dehydration. The dynamic process can be controlled by regulating bubble sizes, distances and packing modes. Various 4D structures have been constructed. Combined with the 3D printing technique, this proof-of-concept study may open new avenues for bio-engineering and beyond.

Stretchable Multiresponsive Hydrogel with Actuatable, Shape Memory, and Self-Healing Properties

Smart hydrogels with responsive behaviors have attracted tremendous attention. However, it is still a challenge to synthesize stretchable hydrogels capable of changing their original properties in response to multiple external stimuli. Here, integration of actuation function, shape memory, and self-healing capability in a highly stretchable hydrogel under triple external triggers is achieved by rationally engineering multiple functional moieties. The hydrogel exhibits high stretchability (average relative strain (mm/mm) is >15) and excellent fatigue resistance during 100 loading cycles of 100% strain. Incorporating a moisture-insensitive polymer film with the hydrogel, hydroactuated functionality is demonstrated. Moreover, shape memory and self-healing abilities of the hydrogel are realized by the formation of ionic crosslinking or dynamic borate ester in conditions of multivalent cations and pH, respectively. Deformable plastic flowers are displayed in this work as a proof-of-concept, and it is believed that this smart hydrogel could be used in plenty of frontier fields, such as designing electronic devices, soft robotics, and actuators.

Hydrogel microfibers with perfusable folded channels for tissue constructs with folded morphology

Perfusable microfibers with folded channels are generated to fabricate small intestine and skeletal muscle constructs for tissue engineering.