Sponge is one of the oldest creatures on earth, and it is an interesting gift from nature to mankind. Natural sponges are the simplest aquatic multicellular animals in the world. There are many types and different shapes, and most of them live on the bottom of the sea.
The murals on the island of Crete in ancient Greece record people’s initial recognition and use of natural sponges. Since the Middle Ages, in addition to being used as a cleaning material, natural sponges have gradually been used in many fields such as painting and medicine. Although there are tens of thousands of species of sponge animals, only more than 10 kinds of natural sponges have been used by humans in the past 2000 years.
In fact, the natural sponges we commonly use are the needle-like inner bones of some sponges. According to different types, these endoskeletons are rich in inorganic salts such as calcium or silicon or network protein fibers. Under the influence of the environment, these endoskeletons form a very special porous structure and become the support of sponge life.
Relying on this porous structure, the sponge can take in oxygen, microorganisms and inorganic salts in seawater, excrete metabolites, and reproduce. On the other hand, the endoskeleton of sponges and their porous structure endow them with the characteristics of “rebirth” after death, that is, when they leave the sea and lose their life, they still maintain elasticity, rigidity and hydrophilicity: they look like in a dry state. A mass of rotten cotton can resist a certain external force when rubbed; and when it re-enters the water, it immediately restores its plump and soft state, as if reborn.
Artificial sponge came into being
Since the 1950s, the price of natural sponges has remained high, and over-exploitation has exacerbated the production crisis of natural sponges. As some of the magical “codes” of sponges have been accelerated by scientists, various artificial sponges and related products have begun to enrich people’s production and life.
The industry generally believes that the original artificial sponge originated from a cheap flexible polyurethane foam material developed by Bayer in Germany in 1952. Although these materials are foamed plastics synthesized from a variety of chemical components, their appearance is very similar to natural sponges, full of interconnected pores, soft to the touch, and has a certain degree of elasticity and water absorption capacity, which can replace natural sponges in some occasions use. The sponge developed by Bayer greatly encouraged people to further synthesize or process artificial sponge materials with similar structures.
In terms of composition, various polyurethane foam materials are still one of the representative artificial sponge varieties, which are widely used in the furniture manufacturing, automobile industry, shoe industry, art industry, and even the aerospace field. People can obtain polyurethane sponges with different functions by adjusting the formulation of raw materials. For example, polyester polyurethane sponges have good tensile properties, solvent resistance and high temperature resistance, while polyether sponges have good hardness, elasticity and Hydrolysis resistance, more suitable for low temperature occasions.
And once it became a memory foam for astronauts, it was only because of the addition of some silicone oil and other ingredients in its synthetic formula, which changed the viscoelasticity and temperature characteristics of the polyurethane sponge. Adding functional ingredients such as flame retardants and conductive materials to the raw material formula can also further expand the use of polyurethane sponges. Through performance analysis and parameter optimization of the foaming process, the performance and processability of the polyurethane after molding can be fully adjusted. People then send them to their respective uses based on these performance indicators.
Another type of sponge commonly used in daily life is made by foaming wood cellulose fibers or pulp fibers. This is a relatively environmentally friendly sponge material. Its skeleton component gives the product more hydrophilicity and elasticity. The texture is hard in the dry state, and its dense and fine porous structure can make full use of the capillary principle to quickly complete the water. The adsorption and desorption process.
Sponges used in the medical field are mostly made of biocompatible ingredients. For example, scientists enzymatically hydrolyze and purify natural bovine Achilles tendon to extract collagen, and then synthesize porous sponge material through polymer interpenetrating network technology. This sponge material has been used in clinical hemostasis, anti-infection, cartilage repair, and anti-bacterial modified polyvinyl formal sponge has also been widely used to promote wound healing.
Unlike natural sponge ingredients, most synthetic artificial sponges can be regarded as petroleum sponges (that is, sponges whose raw materials are derived from petroleum). However, in the past 30 years, while petroleum sponges have become popular, the homes that natural sponges rely on have been gradually destroyed by human oil exploitation and utilization activities, which has also brought challenges to human survival. For this reason, mankind is striving to develop materials with oil-water separation capabilities, and try to make up for the losses caused by offshore oil leakage and pollution.
As a result, sponge polymer materials with a huge surface area and a loose porous structure have once again entered people’s field of vision. People treat the surface of the material to obtain special wettability and change its ability to be hydrophilic and lipophilic. One of the representative ones is the fluorine-substituted polyvinyl alcohol foam material developed by the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences. The swelling properties and surface properties of the polymer itself give it super oil absorption and super high separation efficiency, and the loose porous sponge state can make it withstand repeated extrusion and can be reused. This research result is expected to provide a new path for offshore oil pollution disposal after accelerating engineering.
Natural sponge contains a huge “treasure”
Although natural sponges once became economic animals for large-scale breeding, the high-quality and cheap artificial sponges eliminated the traditional economic value of natural sponges. However, with the development of science and technology, people have discovered the huge “treasure” contained in natural sponges and put forward the concept of “sponge biotechnology”.
Natural sponges have a certain ability to degrade seawater pollutants, and their degradation mechanism and purification capabilities need to be further explored and utilized. Perhaps in the future, people only need to cultivate certain natural sponges on a large scale to achieve the purpose of maintaining the ecological balance of regional waters.
Since the body contains the most abundant marine active substances, the extraction, analysis, processing and utilization of the chemical components of natural sponges has become a hot spot in the development of marine drugs. Relevant studies have shown that it plays a positive role in the treatment of neurological diseases and cancer.
In addition, the microstructure, characteristics, and growth mechanism of sponge spicules continue to arouse the research interest of biologists and bionic scientists. People have studied the light guiding effect shown by sponge spicules at the molecular level, providing new ideas for optical fiber manufacturing. The bionic functionalization work based on natural sponges also provides new research opportunities for experts in the fields of medicine, environmental protection and smart materials. In this regard, Harvard University’s artificial total synthesis of the natural anti-cancer ingredient “Haichondrin” is at the forefront of the world.
The precious natural sponge is a gift from the ocean to people, and it has also made a huge sacrifice for the development of human science and technology. At present, in addition to accelerating scientific and technological research and development, people also need to increase efforts to protect the living environment of natural sponges. Only when people and nature coexist harmoniously can they seek rapid development.