Fabrication of an Electrically Conductive Adhesive for Skin Mounted Bioelectronic Devices

Background: Skin mounted bioelectronics are difficult to integrate with the skin since biocompatible adhesives are not conductive or unsuitable for long-term use. Skin conformability is essential but strong adhesives can damage soft tissue in younger and frail individuals as well as the device during removal. Developing a noninvasive long-lasting biocompatible conductive adhesive for skin that can be used with bioelectronics allows for better treatment options and the improvement of patient outcomes. Methods: This study creates a soft hydrogel using graphene oxide flakes (GO) and polyvinyl alcohol. Networked GO is reduced in a solution of sodium dithionite and sodium hydroxide to form a conductive network within the hydrogel. Adhesive properties are achieved by incorporating a polyacrylic acid polymer into the hydrogel with the addition of N-hydroxysulfosuccinimide (NHS) groups to the polymer. NHS reacts with amine groups found on tissue to form covalent bonds that can be released with a biocompatible trigger solution of sodium bicarbonate and glutathione. Results: Hydration of the hydrogel at 65°C demonstrated that the hydrogel swelled anistropically with swelling ratios of 1.05/1.06/5.5 (length/width/thickness). This showed that the hydrogel can integrate into various surfaces without deformation. The hydrogel demonstrated an impedance of 106.1~164.6 Ω⋅m (20~500 Hz), which is comparable to conventional devices. The hydrogel was chemically bound to amine functionalized polydimethylsiloxane (PDMS) and glass. Peel test showed peak adhesion forces of 100.5 N⋅m-1(Force⋅Width-1) when bound to PDMS or glass. Signal quality of the hydrogel showed that the hydrogels demonstrated ECG and EMG signals comparable to commercially available materials. Conclusions: The importance of this study is to create a soft material that bonds between electrodes and skin. The results demonstrate that the hydrogel has electrical characteristics comparable to conventional electrodes for use in ECG and EMG. In addition, it can create adhesion via chemical bonds that can be released on demand.

Preparation of Silver Nanopowders and Its Application in Low Temperature Electrically Conductive Adhesive

Printable electrically conductive adhesive with high electrical conductivity and good mechanical properties has wide application prospect in electronic device. In order to explore new conductive fillers of interconnecting materials in electronic circuit and electronic packaging industries, silver nanopowders were prepared by DC arc plasma method with high pure. The silver nanopowders present a spherical structure, the particle’s diameter range from 15 to 220 nm. In this paper, a high performance electrically conductive adhesive (ECA) was prepared. This ECA was fabricated by mixing silver nanopowders with epoxy resin and was screen-printed to a required shape. It was found that the ECA can be solidified through a low temperature sintering method in the air at 150 ℃ for 10 min. The electrical and mechanical of above ECA were investigated and characterized. The ECA filled with 75% silver nanopowders exhibits excellent performances, including high electrical conductivity (9.5×10-4 Ω·cm), high bonding strength ( 8.3 MPa). Based on the performance characteristics, the ECA applications in flexible printed electrodes and interconnecting materials are demonstrated.

Development of Multi-Layer Circuitry Using Electrically Conductive Adhesive and Low-Temperature Solder Material for Surface-Mount Component Attachment

The increased versatility in the design and manufacturing of components in low volumes, as well as the shorter time between design and prototype, has increased interest in the field of additively printed electronics. The ability to directly print on a variety of substrates, whether rigid, flexible, or conformable, provides several benefits over conventional electronics fabrication methods. Furthermore, the growing complexity of flexible electronics necessitates the development of multilayered circuits similar to traditional PCBs to decrease the volumetric and gravimetric effect of the underlying electronics. Using z-axis interconnections with dielectric materials, which may allow or prevent the connection between two layers, is one method of reaching several layers of circuits. In this paper, a working multilayer circuitry test vehicle is designed and additively printed using the direct-write method. The circuit model involves conductive and dielectric ink printing, as well as passive and active component attachments using an electrically conductive adhesive (ECA) and low-temperature solder (LTS). The study also shows details about the process of developing dielectric printing parameters for microvias for multilayer z-axis interconnections.

Recent Advances on Thermally Conductive Adhesive in Electronic Packaging: A Review

The application of epoxy adhesive is widespread in electronic packaging. Epoxy adhesives can be integrated with various types of nanoparticles for enhancing thermal conductivity. The joints with thermally conductive adhesive (TCA) are preferred for research and advances in thermal management. Many studies have been conducted to increase the thermal conductivity of epoxy-based TCAs by conductive fillers. This paper reviews and summarizes recent advances of these available fillers in TCAs that contribute to electronic packaging. It also covers the challenges of using the filler as a nano-composite. Moreover, the review reveals a broad scope for future research, particularly on thermal management by nanoparticles and improving bonding strength in electronic packaging.