Imagine a washable hat that can help a visually impaired person perceive changes in a traffic light, or a piece of clothing that can act as a tour guide for the wearer as they navigate the museum.
These incredible scenes, which seem far away from us, may be close at hand.
A research team from Nanyang Technological University, the University of Chinese Academy of Sciences, and the Chinese Academy of Sciences has successfully developed such a "black technology" electronic fiber. It can be woven into clothing and has demonstrated excellent performance in traffic sensing, heart rate monitoring, and more.
It is worth mentioning that this electronic fiber can not only stretch hundreds of meters without defects and has excellent durability, but it is also waterproof and suitable for underwater applications.
相关研究论文以“High-quality semiconductor fibres via mechanical design”为题，刚刚发表在权威科学期刊 Nature 上。
In a concurrent news and opinion piece, Virginia Tech associate professor Xiaoting Jia and her student Alex Parrott said the technology's manufacturing equipment maturity for industrial applications, as well as its widespread use in the textile industry, give it the potential for commercialization. According to them, the work "represents a leap forward in the direction of embedding microcomputers into everyday clothing." ”
Background:
Semiconductors represented by silicon germanium are the "brain" of the modern electronics industry - an indispensable key material for chips. These inorganic semiconductors have incomparable advantages in terms of chemical and thermal stability, electrical properties, and large-scale production. However, under the new trend of the electronics industry embracing flexibility, the intrinsic brittleness of these semiconductors has brought considerable challenges to scientists and engineers. In recent years, the international academic community has put forward some solutions from the aspect of reducing the dimension. For example, the three-dimensional silicon "dots" that can be regarded as zero-dimensional forms are distributed on the flexible substrate in the form of arrays to form a network of soft and hard cross-links to achieve flexibility of brittle and hard materials, or the thickness of the wafer can be reduced and the mechanical damage is passivated, so as to obtain a two-dimensional silicon film that can be bent. However, relatively few studies have been conducted on one-dimensional morphology of semiconductor fibers, mainly due to the extremely difficult preparation. In this regard, although there are examples of melt-based crystal growth methods, such as the micro-drawdown method, the fabrication of semiconductor fibers still faces some significant challenges. The key challenge is how to continuously manufacture crack-free semiconductor fibers of comparable lengths at high volumes on a large scale.
Highlights of this article:
Recently, the team of Associate Professor Wei Lei/Academician Gao Huajian of Nanyang Technological University in Singapore, the research team of Yang Chunlei/Chen Ming of Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, and the team of researcher Zhang Qichong of Suzhou Institute of Nanotechnology and Nanomimicry, Chinese Academy of Sciences, cooperated to form fibers in three stages (viscous flow, Guided by the theoretical study of the stress distribution and capillary instability of core crystallization and subsequent cooling, the fiber flexibility technology of brittle inorganic semiconductor materials has been broken through through the mechanical matching principle of core semiconductor materials and shell materials, and the continuous preparation of ultra-long, fracture-free and disturbance-free inorganic semiconductor fibers has been realized. Then, the newly developed convergent thermal drawing method was used to integrate semiconductor fibers into composite structures of conductors, semiconductors, and insulators with different designs, and the resulting photofibers exhibited a responsivity of up to 0.55 A W-1 and a response time as short as 900 ns at a bias voltage of 2 V, which was comparable to that of commercial planar photodetectors, and solved the compatibility problem of high-performance inorganic semiconductor materials with fibers prepared by thermal drawing method. The results were published in Nature with the title of High-quality semiconductor fibres via mechanical design, with Wang Zhixun, Li Dong, postdoctoral fellows of Nanyang Technological University, and Wang Zhe, professor of Jilin University, as co-first authors, associate professor Wei Lei/academician Gao Huajian from Nanyang Technological University, and associate researcher Chen Ming of Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences. Qichong Zhang, a researcher at the Suzhou Institute of Nanotechnology and Nanobionics of the Chinese Academy of Sciences, is the co-corresponding author.
As an emerging application form of inorganic semiconductor materials, one-dimensional fiber has the unique advantages of fineness and flexibility, which provides a new possibility for the seamless integration of flexible electronic devices and people's daily clothing, and the non-inductive link between flexible electronic devices and daily life. However, fast and ultra-long technologies for the preparation of high-quality semiconductor fibers remain a huge challenge for the scientific community. Inspired by the traditional optical fiber preparation and hot drawing process, the research team extended the hot drawing method of single-material fibers to a multi-material preparation process, and solved the stress mismatch and fluid instability of multi-material systems in the thermal drawing process of inorganic semiconductor fibers from the perspective of solid mechanics and fluid mechanics, and successfully realized the preparation strategy of silicon/germanium semiconductor fibers with high-speed drawing of several meters to tens of meters per minute for hundreds of meters.
Figure 1. The stresses in high-quality inorganic semiconductor fiber core materials are mainly caused by the difference in volume between the core and the cladding, which results from core solidification and mismatched thermal expansion. Perturbation before core solidification is caused by capillary instability. These mechanisms are further supported by modeling and finite element simulations, and such stresses and instabilities can be mitigated and suppressed by rational mechanical design through material selection and process optimization. The mechanical design of the melt core method provides a new research direction for the development of high-quality semiconductor fibers, and is expected to be extended to a wider range of materials.
Figure 2. The research team further adopted the convergent thermal drawing method to establish a tight and stable material interface between the insulator, conductor and semiconductor in the fibers of hair thickness, and completed the assembly and packaging of the device during the drawing process. This flexible and stable fibrous photodetector can be used alone or woven into fabrics, so as to turn passive clothing into functional "smart" wear, which will have broad application prospects in the future in the fields of smart wearables, metaverse, artificial intelligence, extreme environment sensors, brain-computer interfaces, etc.
Figure 3. High-performance semiconductor fiber photodetectors and applications
Summary and outlook
This work clarifies the mechanical interaction of 'core-cladding' for the first time, and breaks through the fiber flexibility technology of brittle inorganic semiconductor materials through the mechanical matching principle of core semiconductor materials and shell materials, and realizes the continuous preparation of ultra-long, fracture-free and disturbance-free inorganic semiconductor fibers. This work provides new insights into extreme mechanics and fluid dynamics that are unattainable in traditional materials and device morphologies, and is expected to contribute to addressing the growing demand for high-performance flexible semiconductor materials and wearable electronics.
Washable, high-performance flexible fibers
The most important thing is the abrasion resistance of the fiber: it must be flexible enough to twist easily for weaving, in addition, it must be washable and reusable, and it must be breathable for people to wear comfortably.
Many researchers are doing these things simultaneously by creating smart fiber optic devices made of amorphous semiconductor materials. The problem is that existing manufacturing methods can produce threads with broken, defective semiconductor cores that affect the performance of the fibers.
This time, they discarded the shortcomings of traditional methods and adopted an innovative way to introduce tiny semiconductor devices into the fiber, creating a flawless fiber at the level of 100 meters.
This innovative technology draws on industry standards for fiber optic fabrication and leverages tools widely used in the textile industry. Through a series of ingenious steps, the researchers not only created soft fibers with photoelectric properties, but also seamlessly embedded them into everyday clothing.
You can imagine that the hat is embedded with such fibers that are able to sense the signal of a traffic light and alert the wearer through a mobile phone, which is very friendly to the blind.
Or, a sweater not only keeps warm, but also acts as an optical communication device, transmitting information through Li-Fi technology.
In addition, the research team even knitted these soft electronic fibers into bracelets. It fits better on the wrist and is more durable than existing equipment, and can work well under pressures up to 3000 meters underwater.
Although the advent of soft electronic fibers has brought unprecedented innovation to the field of wearable devices, however, this research has some limitations and challenges.
For example, while the study overcame the problem of semiconductor devices being prone to breakage during fiber fabrication, the outer material of the fiber at the expense of some practicality, especially in apparel applications where softness and breathability need to be maintained. This puts forward higher requirements for the selection of outsourcing materials.
In addition, on the production side, the current technical route requires post-processing of the fibers to separate them from the outer material, which may increase production costs and have an impact on environmental friendliness.
In addition, in order to ensure the high quality of the fibers, the research team adopted the processing method of adding single crystalline semiconductors at a later stage, which limited the availability and production efficiency of the materials to a certain extent.
Wearables, the possibilities are endless
The birth of flexible electronic fibers is not only a scientific and technological breakthrough, but also a new attempt to integrate fashion and technology.
Jia and Alex Parrott point out that the equipment used to make these fibers already includes a fiber traction device, which is already widely used in the telecommunications industry to produce commercial fibers. Once these fibers have been prepared, they can be skillfully woven into a variety of fabrics using tools that are already widely used in the textile industry.
An exciting direction in the future, they say, is to equip fibers with more complex devices, such as transistors, and to increase the density of these functional elements. One limitation of the current method is that it requires a post-processing step to incorporate extremely high-quality (single-crystal) semiconductors into the fibers.
In addition to using new fibers to integrate wearables into everyday life, wearables have other possibilities.
In December last year, the team from Nankai University developed a two-way temperature regulation clothing system that can be powered by solar power throughout the day, which can extend the thermal comfort zone from 22°C to 28°C to 12.5°C to 37.6°C through rapid thermal regulation, and has a rapid thermoregulation rate, so as to ensure the safety and comfort of the human body in various complex and unstable environments.
According to reports, the system can increase human survivability in harsh environments such as polar regions and individual spacewalks, providing a variety of possibilities for expanding human adaptability to harsh environments.
In June 2022, a team of researchers from Nanyang Technological University and Tsinghua University in Singapore jointly developed a stretchable, waterproof "fabric" that converts the energy generated by the movement of the human body directly into electricity. After washing, folding and pleating, the fabric does not deteriorate in performance and can even maintain a stable power output for up to 5 months.
Seeing this, you might as well imagine that in the near future, we will no longer wear ordinary clothes, but smart fabrics that can seamlessly connect, interact with the surrounding environment, and self-power, and at that time, what will our daily lives be like?
Source | Network integration
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