Formation mechanism analysis and experimental investigation of single-step printing customized circuits by liquid-metal direct writing

Liquid-metal direct writing is a cost-effective and green technology, which is very promising for the customized fabrication of flexible circuits and functional devices. However, owing to the high surface tension of metal ink, the printed circuits are prone to intermittent outflow, large forming size error, and unstable forming. The smooth flowing and conveying of liquid-metal ink are still huge challenges that need significant attention. Herein, the force mechanism of liquid-metal ink transported by ball rotation and translation of the printing head was analysed, and the wetting characteristics of liquid metal on the surface of different substrates and its influence on forming morphology were investigated. The stable output printing of gallium indium alloy (GaIn24.5) liquid metal was realized. The changing characteristics of the shape and size of the liquid-metal circuits formed under different printing speeds and writing pressures were experimentally studied. The effective process window for obtaining the best circuit quality was established. Based on this, a flexible printed circuit board and functional electronic pattern were successfully printed under the writing pressure W=1 N and printing speed F800 mm min−1. The printed lines of GaIn24.5 exhibited a smooth surface, uniform width, small size error, and ability to connect electronic components and conduct electricity. This research proposes a new technical approach for customized printing of personalized electronic circuits and has important application prospects in the future.

Self-sintering liquid metal ink with laponite for flexible electronics

Liquid-metal (LM)-based flexible and stretchable electronics have attracted widespread interest in soft robotics, self-powered devices and electronic skins. Although nanometerization can facilitate deposition and patterning of LMs onto substrates, subsequent...

Flexible RFID Tag Inductor Printed by Liquid Metal Ink Printer and Its Characterization

In order to fulfill various growing needs of application fields, the development of low-cost directly printable radio-frequency identification (RFID) tag is essential for item level tracking. Currently, there lacks an easily available way to directly write out functional consumer electronicslike typewriting on paper by an office printer. Here, we show a desktop printing of RFID tag inductors on flexible substrates via developing liquid metal ink and related working mechanisms. The directly printing inductor on various flexible substrates with extremely low cost and rapid speed was designed based on the sympathetic oscillations of multiple LC (inductor–capacitor) circuits. In order to better meet the demands of the distinct resonant circuits, a series of conceptual experiments for investigating the relationship between the character of the inductor and its parameters—shape, number of coils, line width, spacing, etc.,—have been designed. The parameters are all working upon the performance of the printed inductors by liquid metal ink printer, and the relationship laws are consistent with those of the conventional inductors. The coils number as the biggest effect factor has a linear relationship with the inductance of the spiral-type inductors. An inductor with excellent properties can be well chosen by adjusting its parameters according to various applications. The present work demonstrated the way for a low cost and easy going method in directly printing RFID tag inductors on flexible substrates.

Liquid Metal Ink Enabled Rapid Prototyping of Electrochemical Sensor for Wireless Glucose Detection on the Platform of Mobile Phone

Pervasive detection of blood glucose is rather critical for the real-time disease diagnosis which would provide valuable guidance for treatment planning. Here, we established a health care platform for this purpose through incorporating the glucose detection with liquid metal printed sensor and the smart phone monitoring system together. The liquid metal ink composed of bismuth indium stannic (BIS) alloy was identified as an appropriate sensor material to be quickly written or printed on polyvinyl chloride (PVC) substrate at around 59 °C to form desired electrodes. It thus eliminated the complicated procedures as usually required in conventional sensor fabrication strategies. The alloy electrodes were characterized via cyclic voltammetry to demonstrate their practical functionality. Further, unlike using the commonly adopted glucometer, a smart phone was developed as the data acquisition and display center to help improve the portability and ubiquitous virtue of the detection system. Glucose solution in different concentrations was assayed via this platform. It was shown that there is a good linear relationship between the concentration and the integral value of the curve recorded by the mobile phone, which confirms the feasibility of the present method. This quantitative point-of-care system has pervasive feature and is expected to be very useful for future low-cost electrochemical detection.

Direct printing and assembly of FM radio at the user end via liquid metal printer

Purpose – This paper aims to demonstrate the practicability of the liquid metal printer, developed in the authors’ laboratory, in the direct manufacture and assembly of circuit boards at the end customer side using GaIn24.5 alloy as printing ink at room temperature. Design/methodology/approach – A practical procedure for printing a real designed frequency modulation (FM) radio circuit on flexible and transparent substrate using liquid metal printer was established. Necessary electronic components are then assembled on this circuit board. To enhance the mechanical stability of the FM radio circuit board, we further package the circuit board using room temperature vulcanizing silicone rubber. Finally, an efficient way to recycle the liquid metal ink and electronic components is presented at the end of circuit board’s life cycle. Findings – Methods of designing the circuit patterns that are applicable to liquid metal printer are similar to the conventional printed circuit board (PCB) designing strategies. The procedure of applying liquid metal printer for printing the circuits is entirely automatic, cost-effective and highly time-saving, which allows the user to print out desired device in a moment. Through appropriate packaging, the FM radio circuit board can be flexibly used. These PCBs own many outstanding merits including easy modification and stretchability. Nearly all liquid metal ink and components can be recycled. Originality/value – The present end-customer-oriented liquid metal printing opens the way for large-scale personal electronics manufacture which is expected to initiate many emerging applications in education, design, industry, entertainment and more maker targets.