Highly Transparent, Flexible Conductors and Heaters Based on Metal Nanomesh Structures Manufactured Using an All-Water-Based Solution Process.

Metal mesh is a promising material for flexible transparent conducting electrodes due to its outstanding physical and electrical properties. The excellent control of the sheet resistance and transmittance provided by the metal mesh electrodes is a great advantage for microelectronic applications. Thus, over the past decade, many studies have been performed in order to realize high-performance metal mesh; however, the lack of cost-effective fabrication processes and the weak adhesion between the metal mesh and substrate have hindered its widespread adoption for flexible optoelectronic applications. In this study, a new approach for fabricating robust silver mesh without using hazardous organic solvents is achieved by combining colloidal deposition and silver enhancement steps. The adhesion of the metal mesh was greatly improved by introducing an intermediate adhesion layer. Various patterns relevant to optoelectronic applications were fabricated with a minimum feature size of 700 nm, resulting in high optical transmittance of 97.7% and also high conductivity (71.6 Ω sq-1) of the metal mesh. In addition, we demonstrated an effective transparent heater using the silver mesh with excellent exothermic behavior, which heated up to 245 °C with 7 V applied voltage.

Highly sensitive metal-grid strain sensors via water-based solution processing.

Strain sensor technologies have been spotlighted for their versatility for healthcare, soft robot, and human-robot applications. Expecting large future demands for such technology, extensive studies have investigated flexible and stretchable strain sensors based on various nanomaterials and metal films. However, it is still challenging to simultaneously satisfy parameters such as sensitivity, stretchability, linearity, hysteresis, and mass producibility. In this work, we demonstrate a novel approach for producing highly sensitive metal-grid strain sensors based on an all-solution process, which is suitable for mass production. We investigated the effects of the width of the metal grid and width/spacing ratio on the piezoresistivity of the strain sensors. The metal grid strain sensors exhibited high sensitivity (gauge factor of 4685.9 at 5% strain), rapid response time (∼18.6 ms), and superior strain range (≤5%) compared to other metal-based sensors. We demonstrated that the sensors could successfully convert voice signals and tiny movements of fingers and muscles into electrical signals. In addition, the metal-grid strain sensors were produced using a low-cost procedure without toxic solvent via an all water-based solution process, which is expected to allow the integration of such metal-grid strain sensors into future highly sensitive physical sensing devices.