Multi‐layer electrical interconnects are critical for the development of integrated soft wearable electronic systems, in which functional devices from different layers need to be connected together by vertical interconnects. In this work, electrohydrodynamic (EHD) printing technology is studied to achieve multi‐layer flexible and stretchable electronics by direct printing vertical interconnects as vertical interconnect accesses (VIAs) using a low‐melting‐point metal alloy. The EHD printed metallic vertical interconnection represents a promising way for the direct fabrication of multilayer integrated electronics with metallic conductivity and excellent flexibility and stretchability. By controlling the printing conditions, vertical interconnects that can bridge different heights can be fabricated. To achieve reliable VIA connections under bending and stretching conditions, an epoxy protective structure is printed around the VIA interconnects to form a core‐shell structure. A stable electrical response is achieved under hundreds of bending cycles and during stretching/releasing cycles in a large range of tensile strain (0–40%) for the printed conductors with VIA interconnects. A few multi‐layer devices, including a multiple layer heater, and a pressure‐based touch panel are fabricated to demonstrate the capability of the EHD printing for the direct fabrication of vertical metallic VIA interconnects for flexible and stretchable devices.
Direct printing of flexible and stretchable conductors provides a low‐cost mask‐less approach for the fabrication of next‐generation electronics. In this work, an electrohydrodynamic (EHD) printing technology is studied to achieve high‐resolution printing of low‐melting‐point metal alloys, which enables low‐cost direct fabrication of metallic conductors with sub 50 µm resolution. The EHD printed microscale metallic conductors represent a promising way to create conductive paths with metallic conductivity and excellent flexibility and stretchability. A stable electrical response is achieved after hundreds of bending cycles and during stretching/releasing cycles in a large range of tensile strain (0–70%) for the printed conductors with properly designed 2D patterns. Due to the low melting point of the metal alloy ink, the printed conductor demonstrates self‐healing capability that recovers from failure simply by heating the device above the eutectic temperature of the metal ink and applying slight pressure. A high‐density touch sensor array is fabricated to demonstrate the high‐resolution capability of the EHD printing for the direction fabrication of flexible and stretchable devices.
more » « less- NSF-PAR ID:
- 10048454
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Technologies
- Volume:
- 3
- Issue:
- 3
- ISSN:
- 2365-709X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
A silver nanowire (AgNW) based conductor is a promising component for flexible and stretchable electronics. A wide range of flexible/stretchable devices using AgNW conductors has been demonstrated recently. High-resolution, high-throughput printing of AgNWs remains a critical challenge. Electrohydrodynamic (EHD) printing has been developed as a promising technique to print different materials on a variety of substrates with high resolution. Here, AgNW ink was developed for EHD printing. The printed features can be controlled by several parameters including AgNW concentration, ink viscosity, printing speed, stand-off distance, etc . With this method, AgNW patterns can be printed on a range of substrates, e.g. paper, polyethylene terephthalate (PET), glass, polydimethylsiloxane (PDMS), etc. First, AgNW samples on PDMS were characterized under bending and stretching. Then AgNW heaters and electrocardiogram (ECG) electrodes were fabricated to demonstrate the potential of this printing technique for AgNW-based flexible and stretchable devices.more » « less
-
more » « less
Abstract This review discusses methods, challenges, and opportunities for direct‐write and 3D printing of low melting point, gallium‐based liquid metal alloys at room temperature. Alloys of gallium exhibit high conductivity and high stretchability making them well suited for use in soft circuitry for stretchable electronics and soft robotics. In addition, the liquid nature of the metal enables entirely new ways to pattern metals at room temperature; herein, the focus is placed on additive printing via nozzle‐based methods. Room temperature printing of liquid metals enables rapid fabrication of complex geometries (with dimensions as small as 10 µm) on a wide range of materials, such as polymers. These processes can be used to make metallic conductors for devices with self‐healing capabilities, soft/stretchable electrodes, and sensors.
-
more » « less
Abstract A unique direct printing method is developed to additively pattern silver nanowires (AgNWs) with length of up to ≈40 µm. Uniform and well‐defined AgNW features are printed on various substrates by optimizing a series of parameters including ink composition, printing speed, nozzle size, substrate temperature, and hydrophobicity of the substrate surface. The capability of directly printing such long AgNWs is essential for stretchable electronics applications where mechanical compliance is required as manifested by a systematic study comparing the electrical and electromechanical performance of printed AgNW features with different nanowire lengths. Such printed AgNWs are used to demonstrate biaxially stretchable conductors, ultrasensitive capacitive pressure sensor arrays, and stretchable electroluminescent displays, indicating their great potential for applications in low‐cost wearable electronics. This strategy is adaptable to other material platforms like semiconducting nanowires, which may offer a cost‐effective entry to various nanowire‐based mechanically compliant sensory and optoelectronic systems.
-
more » « less
Abstract Printed electronics is attracting a great deal of attention in both research and commercialization as it enables fabrication of large‐scale, low‐cost electronic devices on a variety of substrates. Printed electronics plays a critical role in facilitating widespread flexible electronics and more recently stretchable electronics. Conductive nanomaterials, such as metal nanoparticles and nanowires, carbon nanotubes, and graphene, are promising building blocks for printed electronics. Nanomaterial‐based printing technologies, formulation of printable inks, post‐printing treatment, and integration of functional devices have progressed substantially in the recent years. This review summarizes basic principles and recent development of common printing technologies, formulations of printable inks based on conductive nanomaterials, deposition of conductive inks via different printing techniques, and performance enhancement by using various sintering methods. While this review places emphasis on conductive nanomaterials, the printing techniques and ink formulations can be applied to other materials such as semiconducting and insulating nanomaterials. Moreover, some applications of printed flexible and stretchable electronic devices are reviewed to illustrate their potential. Finally, the future challenges and prospects for printing conductive nanomaterials are discussed.
