Electrospining Machine: Liquid metals and electrospun nanofibres: a magical combination for wearable electronics

 Literature introduction

Unlike conventional rigid electronics, flexible, stretchable electronics have attracted much attention because they can be mechanically compatible with a wide range of objects. The integration of liquid metals (LM), intrinsically stretchable conductive materials, and electrostatic spinning has emerged as a cutting-edge approach for the preparation of flexible, stretchable, and breathable electronics. Due to their inherent properties, LMs inevitably suffer from a number of problems when combined with electrostatically spun substrates, such as poor interfacial integration or leakage. Therefore, great efforts have been devoted to solving the challenges that exist between LM and electrostatically spun substrates in order to obtain flexible, stretchable electronics with excellent properties to meet the requirements of different areas of use.

Key Highlights of Our Groundbreaking Research

1. For the first time, various strategies for preparing flexible, stretchable electronic devices based on electrostatic spinning LM are summarised. The advantages and problems of each strategy are also highlighted.

2. The achievements of flexible, stretchable electronics based on electrospun LM are summarised for various interdisciplinary applications in stretchable circuits and displays, stretchable sensors, epidermal electronics and energy harvesting devices.

3. The future development of wearable electronics based on electrostatically spun LM can be focused on interface interaction, packaging, recyclability and multifunctional integration for complex application conditions.

What are the main challenges facing liquid metals in wearable electronics devices?

1.High surface tension: 

Liquid metals have a high surface tension, which makes them tend to form spheres in free space. This property makes it difficult to form strong bonds with the electrospun materials, thus limiting their electrical properties in the tensile state.

2. Interfacial interactions: 

Poor interfacial interactions between liquid metals and electrospun nanofibrous membranes may hinder the performance of stretchable electronic devices. Improving this interfacial bonding is essential to enhance the electrical properties of the material in the stretched state.

3.Oxidation issues: 

In environments with oxygen levels above 20 ppm, amorphous or poorly crystallised oxides may form on the surface of liquid metals. While these oxides can reduce surface tension, they can negatively affect the electrical conductivity of the liquid metal.

4. Leakage issues:

 Because liquid metals are in a liquid state at room temperature, there is a risk of leakage during preparation and application, which poses a challenge for their use in wearable devices.

5. Long-term stability:

Although there are several ways to improve interfacial bonding, achieving robust and stable stretchable electrodes for long-term use remains a major challenge.

A review of preparation strategies and applications of LMS-based electrospun flexible and stretchable electronic devices

How does nanofber machime enhance the properties of liquid metals?

1. Improvement of interfacial bonding: 

The interfacial interaction between liquid metals and electrospun nanofibre membranes is poor due to the high surface tension of liquid metals. Future research should focus on developing methods to enhance this interfacial bonding, e.g. by coating the surface of electrospun fibres with metallic substances (e.g. silver) or alloying liquid metals with other elements to improve compatibility.

2. Robustness and durability: 

There is a need to investigate the long-term stability and durability of electrospun liquid metal-based stretchable electronic devices. Research should aim to address challenges related to the mechanical robustness of these materials under repeated deformation and environmental conditions.

3. Advanced coating technologies:

Exploring advanced coating technologies to improve the adhesion and conductivity of liquid metals on nanofibres could enhance performance. This includes the use of various bonding materials or innovative surface treatments to enhance the interaction between liquid metals and polymer substrates.

4. Multifunctional materials:

Future research could focus on the development of multifunctional materials that not only provide electrical conductivity, but also additional properties, such as sensing capabilities, self-healing properties or enhanced thermal management. This could extend the range of applications for these materials in smart electronic devices.

5. Scalability and manufacturing technologies:

Research should also focus on the scalability of production methods for electrospun liquid metal-based materials. The development of cost-effective and efficient manufacturing processes is essential for commercial applications.

6. Application-specific research:

Investigating specific applications of electrospun liquid metal-based stretchable electronic devices, such as in health monitoring, flexible displays or soft robotics, can provide insights into the unique needs and challenges in these areas.

Direct writing and transfer printing (a) Schematic of direct writing of LMs on electrospun nanofibre films and optical and SEM images of the printed patterns. (b) Schematic design of transfer printing fabrication process

Applications for scalable circuits and displays

Original link: https://doi.org/10.1016/j.nanoen.2024.110078