Figure Electrospinning principle diagram
Electrospinning technology is a one-dimensional nanofiber preparation technology. Its advantages are simple manufacturing device, low spinning cost, many types of spinnable polymers, and controllable spinning process. The basic principle is: in a high-voltage electrostatic field, when the electric field force of the charged polymer solution or melt droplet is greater than the surface tension, the polymer is drawn and refined under the action of the electric field, and this process is accompanied by solvent evaporates and the fibers solidify to form nanofibers, which are recently deposited on the receiving device. Electrospun nanofibers, as a kind of nanomaterials, have the characteristics of high specific surface area, large aspect ratio and high porosity. They are used in filtration separation (air filtration, water filtration, cell filtration, oil-water separation), biomedicine (tissue engineering, Drug release, wound repair), nanocatalysis (photocatalysis, electrode catalysis, enzyme catalysis, precious metal catalysis), sensors (vibration frequency sensor, resistance sensor, photoelectric sensor, optical sensor, ampere sensor), new energy (dye-sensitized solar energy) Battery photoanode materials and electrolyte materials, lithium ion battery diaphragm and electrode materials), nano luminescent materials (oxide semiconductor luminescent materials, sulfide semiconductor luminescent materials, rare earth element doped luminescent materials, organic luminescent materials), magnetic materials (ferrite Bulk nanofiber magnetic materials, metal nanofiber magnetic materials, inorganic/polymer composite nanofiber magnetic materials), composite reinforcement materials, food packaging materials, cosmetic materials (beauty masks), sound-absorbing materials, high-temperature thermal insulation materials (inorganic ceramic nanofibers) ), nano-carbon fiber and other fields, have broad application prospects.
Figure Nanoscience and technology
Nanoscience and technology is the study of the properties and interactions of substances (including atoms and molecules) on the nanometer (1nm=10-9m) scale (between 0.1nm and 100nm), as well as multidisciplinary high-tech technologies that utilize these properties. The ultimate goal is to directly manufacture products with specific functions based on the characteristics of atoms and molecules on the nanoscale and substances on the nanoscale, and achieve a leap in production methods. Nanoscience generally includes the research fields of nanoelectronics, nanomechanics, nanomaterials, nanobiology, and nanochemistry.
Figure Electrospun nanofiber SEM
The size of nanofibers is widely defined, and there is currently no standard definition. In a narrow sense, nanofibers refer to fibers with a diameter in the range of 1-100nm. Broadly speaking, fibers below 1um can be called nanofibers. In addition, from the perspectives of spinning technology, cost, and practicality, generally, fibers that contain nanostructures and are endowed with new physical properties can also be classified as nanofibers, such as fibers doped with functional nanoparticles (already Used in various functional fibers such as antibacterial, flame-retardant, anti-ultraviolet, far-infrared, antistatic, electromagnetic shielding, etc.). The size effect of nanofibers is very significant, showing many novel properties in light, heat, magnetism, electricity, etc., so it has received great attention from researchers and is expected to be used in clothing, food, medicine, energy, electronics, paper, aviation and other fields . Electrospun nanofibers are difficult to exist alone. They usually exist in the form of nanofiber aggregates and nanofiber membranes, which are similar to common plastic films, non-woven fabrics and other membrane materials. They are essentially plastic or inorganic (inorganic nanofibers membrane), there is no special toxicity in itself, so you can use it with confidence.
Figure ZnO Nanopowder
Nanomaterials can be roughly divided into four categories: nanopowder, nanofiber, nanomembrane, and nanobulk.
Nano-ceramics: Nano-ceramic materials developed by using nano-technology use nano-powders to modify existing ceramics. By adding or generating nano-scale particles, whiskers, wafer fibers, etc. into the ceramics, the crystal grains, grain boundaries, and their combination between them has reached the nanometer level, which greatly improves the strength, toughness and superplasticity of the material.
Nano powder: also known as ultrafine powder or ultrafine powder, generally refers to powder or particles with a particle size of less than 100 nanometers. It is a solid particle material in an intermediate state between atoms, molecules and macroscopic objects.
Nanofiber: refers to a linear material with a nanometer diameter and a large length. Electrospinning is a simple and feasible method for preparing nanofibers.
Nano film: Nano film is divided into particle film and dense film. The particle film is a thin film in which nanoparticles are stuck together with very small gaps in the middle. Dense film refers to a thin film with a dense film layer but with a nano-level crystal grain size.
Nano-bulk: Nano-bulk is a nano-crystalline material obtained by high-pressure molding of nano-powder or by controlling the crystallization of liquid metal. The main uses are: ultra-high-strength materials; smart metal materials, etc.
Figure Four types of nanomaterials
The broad definition of nanomaterials is: at least one dimension in the three-dimensional space is at the nanometer scale (nanophase materials) or structural materials composed of them as basic units (nanostructured materials). The basic units of nanomaterials can be divided into four categories: zero-dimensional, one-dimensional, two-dimensional and three-dimensional. Zero-dimensional means that the size of the material in the three dimensions of space is nano-scale, such as nanoparticles and atomic clusters; one-dimensional means that the size of the material in both dimensions of space is nano-scale, such as nanorods, nanotubes and nanofibers ; Two-dimensional means that the size of the material is nanoscale in only one dimension of space, such as nanosheets, ultra-thin films, multilayer films, and superlattices. Three-dimensional refers to the three-dimensional scale in space, such as nano-flowers and nano-balls.
It may be that the concentration of the spinning solution is too low, or the molecular weight of the polymer is too small.
Electrospinning, also called polymer injection and electrostatic stretching spinning process, is greatly different from traditional ways. Firstly, polymer solution or melt takes with thousands of high-voltage electricity. And electric polymer droplets are accelerated at the top of capillary Taylor cone under the influence of the electric field. Secondly, when the electric field power is strong enough, polymer droplets will inject a thin stream against surface tension, during which solution will evaporate or solidify. Finally the thin stream will be collected by collector, forming a non-woven cloth fibrofelt. During electrospinning process, droplets generally have electrostatic tension in an electric field, and therefore, when injection stream runs from capillary end to collector, it will accelerate, and induces injection stretching in the electric field.