Liquid Metal based Stretchable Room Temperature Soldering Sticker Patch for Stretchable Electronics Integration

Abstract

Researchers are eagerly developing various stretchable conductors to fabricate devices for next‐generation electronics. Most of the major problems in stretchable electronics happen at the connection between rigid and soft parts and the development of reliable soldering material is a major hurdle in stretchable electronics. Though there are attempts to devise new soldering processes for integrating chips and stretchable conductors, they still possess limitations such as mechanical stability, mass production, sophisticated processes, and restricted candidates for conductors and substrates. Here, this study presents a room‐temperature universal stretchable sticker‐like soldering process that can stretchably solder multiple spots at once and directly fabricates a stretchable device in an in situ manner while a target conductor is installed on one's body. The solder developed in this research possesses high conductivity with a unique freestanding feature enabling the process. It can be elongated when directly positioned between a rigid chip and a rigid conductor, demonstrating its extraordinary stretchability. It is expected that this simple but unique stretchable soldering technique utilizing the invented solder will allow the integration of functional stretchable conductors with highly advanced rigid chips for next‐generation stretchable electronics.

Materials-Driven Soft Wearable Bioelectronics for Connected Healthcare

“…Mixing with silver nanowire (AgNW) could highly improve the viscosity of the LMNPs, serving as a roomtemperature soldering process for the connection of rigid chips with soft conductors. 104 The free-standing LM-AgNW stretchable solder sticker (termed as STicker) was patternable yet scalable, making the installation of rigid chips/LEDs into a simply place-press-working manner. The STicker could be stretched over 800% with a high conductivity (7.09 × 10 5 S m −1 ) and is proven to connect a three-by-three LED array and a temperature/humidity sensor module.…”

“…A 26 VIAs and 38 chips integration was further demonstrated with confirmed robustness under biaxial stretching. Mixing with silver nanowire (AgNW) could highly improve the viscosity of the LMNPs, serving as a room-temperature soldering process for the connection of rigid chips with soft conductors . The free-standing LM-AgNW stretchable solder sticker (termed as STicker) was patternable yet scalable, making the installation of rigid chips/LEDs into a simply place-press-working manner.…”

Recent Development of Implantable Chemical Sensors Utilizing Flexible and Biodegradable Materials for Biomedical Applications

“…Won et al 174 have validated the safety of liquid metal embedded elastomers (LMEEs) containing eutectic gallium−indium (EGaIn) liquid metal embedded in a soft rubber matrix, demonstrating their suitability for use in implantable biomedical sensors. Kim et al 175 have presented a roomtemperature, stretchable, sticker-like soldering process utilizing a patternable free-standing liquid AgNW composite thin film. A temperature/humidity sensor module based on this composite has been realized with dimensions compact enough for mounting on a fingernail.…”

Patterned Liquid-Metal-Enabled Universal Soft Electronics (PLUS-E) for Deformation Sensing on 3D Curved Surfaces

“…The first strategy involves the direct deposition of the liquid metals onto the target surface including 3D printing, spray printing, and transfer printing. The 3D printing is realized by adhering the liquid metals extruded from microchannels onto the 3D surfaces. ,− Spray printing is implemented by spraying liquid metal microdroplets onto the 3D surfaces covered with prepatterned masks. − The transfer printing is achieved by precontrolling the adhesion properties of the 3D surfaces, which can involve applying adhesive coatings or laser-assisted deposition. − However, these methods commonly face limitations, such as complex processes and the requirement for additional processing steps. For example, 3D printing and adhesive coatings require precise control of the 3D motion platform to manipulate the movement of microchannels.…”