In recent times, wearable electronics, real-time sensing devices and point-of-care device applications have seen a surge in demand. This demand inherently calls for a more economic and reliable method of mass production. One such robust technique is screen printing that offers advantages in terms of being versatile, economical and easy to use. This technique has been proclaimed to be the best amongst the other additive manufacturing techniques by many research groups. This can be solely attributed to its simple equipment design, requiring a paste for printing purpose, a meshwork for housing the design and a squeegee to carry out printing through an up-and-down motion. This subsequently calls for optimising the parameters such as ink rheology, pore size of the mesh, proper choice of mesh design and motion of the squeeze in order to fabricate electrodes for desired purpose. Due to this technique’s immense potential to open up broad inroads in the domain of flexible electronics, whose concept has radically redefined the perception towards the field of electronics, a review article encompassing an elaborate description on the science and other quintessential parameters involved in this mass printing technique would prove to be extremely useful. In this purview, the review article is compartmentalised into sections encompassing discussion on the manufacturing of different kinds of inks for screen printing applications, substrates used, electrode design and pre-treatment procedures.

Fabrication of screen-printed electrodes: opportunities and challenges

With the arrival of the internet of things and the rise of wearable computing, electronics are playing an increasingly important role in our everyday lives. Until recently, however, the rigid angular nature of traditional electronics has prevented them from being integrated into many of the organic, curved shapes that interface with our bodies (such as ergonomic equipment or medical devices) or the natural world (such as aerodynamic or optical components). In the past few years, many groups working in advanced manufacturing and soft robotics have endeavored to develop strategies for fabricating electronics on these curved surfaces. This is their story. In this work, we describe the motivations, challenges, methodologies, and applications of curved electronics, and provide a outlook for this promising field.

Well-rounded devices: the fabrication of electronics on curved surfaces – a review

Size effect on the subsequent yield and hardening behavior of metal foil

Thermoforming of planar polymer optical waveguides for integrated optics in smart packaging materials

Creating buckling-induced wavy or coiled architecture is a successful route to realize high performance of stretchable piezoelectric devices. However, a systematic analysis of the relationship between piezoelectric potential output, mechanical stress and buckling parameters is still lacking. Here, we quantitatively analyze the piezoelectric and mechanical performance of buckled poly(vinylidene fluoride) (PVDF) nanofibers with respect to the buckling architecture and different force loading using finite element simulation. Our results show that decrease in the buckling angle, arc radius and cross section diameter can increase the piezoelectric potential output of a buckled PVDF nanofiber, and increase in buckling cycles is an efficient way to reduce the mechanical stress on the nanofiber. Besides, a relative stable piezoelectric effectiveness can be obtained when the buckling angle is between 60° and 90°. This research helps to identify an optimized design principle for realizing high stretchability and piezoelectric performance of buckled nanofibers, and provides theoretical support for future applications of buckled PVDF in flexible electronic devices.

Numerical analysis of piezoelectric and mechanical response of buckled poly(vinylidene fluoride) nanofibers for the design of highly stretchable electronics

Stress Analysis of a Stretchable Electronic Circuit

This paper aims to study the effect of the thermoforming process on the assembly of a newly developed stretchable material for electric circuit and LEDs for manufacturing of automotive lighting. The thermoforming process was conducted using a mould developed based on commercially available automotive lighting product. The circuit was initially printed on a flat thermoplastic substrate using screen printing technique prior to the thermoforming process. The quality of the product was investigated before and after thermoforming process through quantitative measurement and visual inspection in terms of the circuit’s resistivity and the electrical conductivity, respectively. The resistivity measurement was conducted by using four point probes instrument to compare the resistivity of the circuit which depends on stretch level of circuit and substrate during the thermoforming process. The stretch level was found to be different along the geometry due to the unsymmetrical geometry of the mould. The electrical conductivity of the circuit was also tested by LEDs illumination through power supply connection. This study shows promising results in applying thermoforming process in the fabrication of 3-dimensional shape product with lower cost equipment.This paper aims to study the effect of the thermoforming process on the assembly of a newly developed stretchable material for electric circuit and LEDs for manufacturing of automotive lighting. The thermoforming process was conducted using a mould developed based on commercially available automotive lighting product. The circuit was initially printed on a flat thermoplastic substrate using screen printing technique prior to the thermoforming process. The quality of the product was investigated before and after thermoforming process through quantitative measurement and visual inspection in terms of the circuit’s resistivity and the electrical conductivity, respectively. The resistivity measurement was conducted by using four point probes instrument to compare the resistivity of the circuit which depends on stretch level of circuit and substrate during the thermoforming process. The stretch level was found to be different along the geometry due to the unsymmetrical geometry of the mould. The electrical con...

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A study on thermoforming process of stretchable circuit and its performance in manufacturing of automotive lighting

Advance of knowledge in material engineering has introduced stretchable electronic materials which can be stretched, bended or twisted and it is beneficial for consumer product manufacturing. This paper aims to study the effect of process combination of standard printing process in surface mount technology and thermoforming process on a stretchable conductive polymer to form a 3-dimensional electronic device. The polymer comprised of silver particles as fillers was prepared to produce a conductive and stretchable behavior which can withstand high temperature deformation. It was printed on a flat substrate using a screen printing technique and then being thermoformed to produce 3-dimensional shape of automotive rear lighting. Mechanical and electrical performances of the thermoformed product were characterized before and after thermoforming process to study the reliability of LEDs assembly with stretchable circuits. Four point probes instrument was used to measure resistivity of the printed circuit which was elongated due to thermoforming process. The elongation of circuit varied throughout the lighting prototype depending on complex geometry of mould. Conductivity of the circuit was also tested by LEDs illumination. Results of microscopy investigation, x-ray imaging and thermal cycling show good performances of LEDs joints. This new manufacturing process of printed circuit offers a promising future alternative method in manufacturing of 3-dimensional electronic device.

A Study on a Stretchable Conductive Polymer of Thermoplastic Automotive Device

Alternative manufacturing process of 3-dimensional interconnect device using thermoforming process

This paper presents finite element modelling of fretting wear under partial slip conditions using combined isotropic-kinematic hardening plasticity model with the emphasized to investigate the cyclic-plasticity behaviour predicted under fretting condition. The model is based on two-dimensional (2D) cylinder-on-flat contact configuration of titanium alloy, Ti-6Al-4V. A number of wear profiles at specific number of wear cycle (6000th, 60000th, 150000th and 300000th) are simulated. Contact pressure, tangential stress, shear stress, equivalent plastic strain, tangential plastic strain and also shear plastic strain are gathered and analysed. It is found that the plastic strain response of the combined isotropic-kinematic hardening plasticity model is slightly higher compare to linear kinematic hardening plasticity model [1].

M.Y.T. Ali

Papers

Stress Analysis of a Stretchable Electronic Circuit

A study on thermoforming process of stretchable circuit and its performance in manufacturing of automotive lighting

A Study on a Stretchable Conductive Polymer of Thermoplastic Automotive Device

Alternative manufacturing process of 3-dimensional interconnect device using thermoforming process

Modelling of Fretting Wear under Partial Slip Conditions Using Combined Isotropic-Kinematic Hardening Plasticity Model