The need for high-precision microprinting processes that are controllable, scalable, and compatible with different materials persists throughout a range of biomedical fields. Electrospinning techniques offer scalability and compatibility with a wide arsenal of polymers, but typically lack precise three-dimensional (3D) control. We found that charge reversal during 3D jet writing can enable the high-throughput production of precisely engineered 3D structures. The trajectory of the jet is governed by a balance of destabilizing charge-charge repulsion and restorative viscoelastic forces. The reversal of the voltage polarity lowers the net surface potential carried by the jet and thus dampens the occurrence of bending instabilities typically observed during conventional electrospinning. In the absence of bending instabilities, precise deposition of polymer fibers becomes attainable. The same principles can be applied to 3D jet writing using an array of needles resulting in complex composite materials that undergo reversible shape transitions due to their unprecedented structural control.

Polymeric nanofiber webs have attained much attention because they can provide high surface area with various functional groups. To obtain the polymeric nanofiber webs, electrospinning is the most attractive method because this can provide the versatility of material selection. However, it is relatively difficult to obtain the nanofiber webs, which have highly reactive functional groups and high mechanical strength with high production rate. Here, the helically probed rotating cylinder (HPRC) system based on syringeless electrospinning and chemical vapor deposition (CVD) is introduced to prepare the polyacrylonitrile (PAN) nanofiber webs, having high functional groups and high mechanical strength in fast production rate. The HPRC system can provide the PAN nanofiber webs in high production rate, and the CVD process can provide high reactive functional groups on the PAN nanofiber. In addition, the nanofiber webs can be applied to diverse potential application fields, which require a high number of functional moieties.

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Chromic dyes responding against external stimuli are useful in various field of applications especially to colorimetric sensors. However, there have been several limitations in generic application because of its cost, stability and reliability. Here, we introduced highly functionalizable polymeric materials as a supporter covalently modified with controlled amount of chromic dyes. The photochromic organic dye (spiropyran) and highly functional thermoplastic polyurethanes (TPU) have been adopted as a representative example. Conventional polymeric solution processes such as film processing, wet-spinning, electrospinning and ink-writing are readily applicable because dye-TPU maintains its own solubility in various organic solvents. Additionally, since the concentration of dye on TPU are precisely controllable, these dye-TPU solution can be adopted in broad range of specific applications, such as secret coding, smart fabric, and chromic polymeric film layer.

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