Identification and dynamic monitoring of electrospinning jet assisted by coaxial laser.

The accurate and rapid detection and recognition of jet features are key to dynamic monitoring and online control of the electrospinning process. In this study, a real-time recognition system based on OpenCV was introduced into a coaxial laser-assisted electrospinning system to solve the difficulties of accurate jet recognition and to promote an image processing algorithm response. The jet images with laser assistance were more clearly visible than those without laser assistance, and a significant contrast in grayscale levels existed in the jet image to help distinguish jet features. Subsequently, separate algorithms were designed for the jet visible length calculation, and the recognized visible length of the jet and algorithm running speed were compared. The average visible length of the jet with laser assistance was 11.49 mm, which increased by 1.59 mm compared to that without laser assistance. In addition, the running time of the algorithm with laser assistance was 24.89 ms, reduced by 14.84 ms compared to that without laser assistance, indicating the effectiveness of laser assistance to promote the accuracy and running speed of the jet image recognition process. Additionally, real-time detection of the jet angles was achieved to identify instances of excessive deflection during the electrospinning process. Overall, this study has significant potential to promote the dynamic monitoring of an electrospinning jet.

Review of Droplet Printing Technologies for Flexible Electronic Devices: Materials, Control, and Applications.

Flexible devices have extensive applications in areas including wearable sensors, healthcare, smart packaging, energy, automotive and aerospace sectors, and other related fields. Droplet printing technology can be utilized to print flexible electronic components with micro/nanostructures on various scales, exhibiting good compatibility and wide material applicability for device production. This paper provides a comprehensive review of the current research status of droplet printing technologies and their applications across various domains, aiming to offer a valuable reference for researchers in related areas.

Fast on-off controlling of electrohydrodynamic printing based on AC oscillation induced voltage.

Stability control of electrohydrodynamic (EHD) printing technology is urgent needed for efficient fabrication of flexible electronics. In this study, a new fast on-off controlling technology for micro droplets of EHD is proposed by applying an AC induced voltage. The suspending droplet interface is broken through quickly, and the impulse current can be significantly reduced from 527.2 to 50.14 nA, which greatly reduces its negative impact on jet stability. What's more, time interval of jet generation can be shortened by a factor of three, while not only significantly improving the uniformity of the droplets, but effectively reducing the droplet size from 195 to 104 µm. Moreover, the controllable and mass formation of micro droplets are realized, but also the structure of each droplet is able to be controlled independently, which promoted the development of EHD printing technology in more fields.

Numerical Simulation of Motion and Distribution Characteristics for Electrospray Droplets.

Electrospray is a typical technology to prepare large amounts of droplets at micro/nano scale. Establishing the relationship between the processing parameters and the motion and distribution characteristics for electrospray droplets is an effective approach to guide the uniform deposition of the electrospray membrane. In this paper, a dynamic model of electrospray droplets based on the fully resolved direct numerical simulation (FR-DNS) method was constructed, and the spatial motion behaviors of charged droplets were simulated. The coupling effect of electric field force, the charge repulsive force, and the gravity on the motion and distribution of electrospray droplets was studied, and the relationship between processing parameters including the applied voltage and distance from the nozzle to the collecting plate and the spatial distribution of charged droplets was clarified in a direct way. The simulation model provided a good approach for the quantitative description of the motion and distribution behaviors for electrospray droplets, which would help to guide the control of the electrospray jet ejection process.

High-performance multifunctional electrospun fibrous air filter for personal protection: A review.

With the increasingly serious air pollution and the rampant coronavirus disease 2019 (COVID-19), preparing high-performance air filter to achieve the effective personal protection has become a research hotspot. Electrospun nanofibrous membrane has become the first choice of air filter because of its small diameter, high specific surface area and porosity. However, improving the filtration performance of the filter only cannot meet the personal needs: it should be given more functions based on high filtration performance to maximize the personal benefits, called, multifunctional, which can also be easily realized by electrospinning technology, and has attracted much attention. In this review, the filtration mechanism of high-performance electrospun air filter is innovatively summarized from the perspective of membrane. On this basis, the specific preparation process, advantages and disadvantages are analyzed in detail. Furthermore, other functions required for achieving maximum personal protection benefits are introduced specifically, and the existing high-performance electrospun air filter with multiple functions are summarized. Finally, the challenges, limitations, and development trends of manufacturing high-performance air filter with multiple functions for personal protection are presented.

Jet Mode Recognition of Electrohydrodynamic Direct-Writing Based on Micro/Nano Current.

The online recognition of jet mode is important for the accurate control and further application of electrohydrodynamic direct-writing (EDW) technology. An EDW system with a current detection module is built for jet mode recognition. The current of the EDW jet is measured to recognize the jet mode when printing patterned structures. Then, a data processing program with a digital Kaiser low-pass filter is developed in MATLAB, via which the noise of the current signal is reduced. The features of EDW current, including the current fluctuation and the peak current intervals, are studied to recognize different jet modes. The current characteristics of three jet modes are investigated: droplet ejection mode, Taylor cone ejection mode, and retractive ejection mode. The Taylor cone ejection mode has the smallest coefficient of variation of peak current. This work provides a good way of designing the optimized control algorithm and of realizing the closed-loop control system, which contributes to enhancing the jet stability and accelerating the application of EDW technology.

Arced Multi-Nozzle Electrospinning Spinneret for High-Throughput Production of Nanofibers.

The stable and continuous ejection of multiple jets with high densities is the key to the application of electrospinning technology. An arced multi-nozzle spinneret was designed to increase the production efficiency of electrospinning. The distribution of the electrical field was simulated to optimize the nozzles' distribution of the spinneret. When the nozzles were arranged in an arc array, a relatively uniform electrical field could be obtained, which was beneficial for the weakening of electrical interference among the nozzles. Under the optimized electrical field, multiple jets from each nozzle could be ejected in a stable and continuous way. With the increase of the applied voltage, the electrical stretching force became larger, and there were fewer bonding structures. The average diameter of the electrospun nanofibers decreased with the increase of the applied voltage. When the distance between the inner nozzle and the collector increased, the charged jets suffered a larger stretching effect, resulting in the decrease of the average diameter of the electrospun nanofibers. The electrospinning current increased with the applied voltage and decreased with the distance between the inner nozzle and the collector, which is an important aspect for the monitoring of electrospinning jets. This work provides an effective way to promote the production efficiency of electrospun nanofibrous membranes.

Measurement and Time Response of Electrohydrodynamic Direct-Writing Current.

The micro/nano current is an important characteristic to reflect the electrohydrodynamic direct-writing (EDW) process. In this paper, a direct-written current measurement system with a high signal to noise ratio was proposed to monitor the charged jets, providing the data basis for the promotion of stability and precision of the EDW jet. The electrical characteristics of the printing process were studied, the electrohydrodynamic direct-written current was associated with the stability of charged jet and the accuracy of direct-written patterns. There was an impulse current when the front end of the jet reached the collector and then a stable jet could be gained. With the increase of applied voltage, the severe fluctuation of measured current increased, the charged jet became more unstable and the accuracy of direct-written parallel lines was lower. The effects of processing parameters on direct-written current were also investigated. The average direct-written current at the stable stage increased as the applied voltage and polymer concentration increased, and it decreased as the distance from the nozzle to the collector increased. This research will promote the development and applications of EDW technology in the fields of micro/nano manufacturing.