[Video Available] Graphite-based Stretchable Conductive Paste

Graphite-based stretchable conductive paste combines stretchable resin with graphite and CNT, allowing for repeated stretching.

We have developed a conductive paste that combines stretchable resin with graphite and CNT, which maintains conductivity through repeated stretching and changes its electrical resistance with stretching. ◎ Volume resistivity: 30Ω·cm² At a length of 2 cm, width of 3 mm, and thickness of 0.2 mm, it has a resistance of about 5 kΩ. ※ Viscosity: 3–5 PS (Not suitable for inkjet printing; intended for dispenser or screen printing) ※ Resistance change rate is approximately three times, and the coefficient of variation is undetermined. ※ The maximum operating temperature currently is 120°C. ⇒ Applications include resistance change sensors, contact sensors, etc. ● Advantages of using graphite-based materials: Conductive inks and paste materials such as nano-metal-based, carbon nanotube (CNT) based, and carbon microparticle-based materials: 1. High performance is expected, but processing and manufacturing methods are expensive, making it difficult for material prices to be low. 2. If graphite-based powder, which is produced in large quantities as a byproduct of carbon fiber, can be used as a conductive material, it would enable the creation of inexpensive pastes. 3. Our company has developed a conductive paste with a basic structure where long CNTs are wrapped around graphite-based fibers. 4. By intertwining both materials in a state that allows for continuous stretching and contracting, the stretchable conductor function is maintained.

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basic information

Our conductive paste is composed of relatively long fibrous graphite-based carbon and added CNT. The main conductive function is provided by the graphite-based fibers, while CNT is effective in small quantities. The limit for carbon black alone is 10 Ω·cm, and for CNT alone it is 20 Ω·cm, but by combining both, we achieve low resistance, obtaining around 7 Ω·cm. With careful adjustment of the additive amount, it is possible to reach 1 Ω·cm; however, in this case, it becomes more like "miso" than a paste, significantly reducing adhesion strength. 2. Application to Fabric Materials We will apply the conductive paste to clothing and explore its use in stretchable bending sensors. - Perform a stretchable base treatment on the uneven surface of the fabric material to create a gentle flat surface. - Form a thin film (about 25 μm) to hold the conductive paste. - Attach electrodes (copper foil tape). - Apply the stretchable conductive paste, and after heat curing, it will become the sensor. - The stretchable conductive paste will not peel off even when the fabric material bends. 4. Heart Rate Sensing By applying stretchable conductive paste and resin sheets and curing them at around 100°C, we will realize a "stretchable resistance change type sensor" that responds to stretching.