Spray-Coating Thin Films on Three-Dimensional Surfaces for a Semitransparent Capacitive-Touch Device.

Area of Science:

• Materials Science
• Nanotechnology
• Conductive Polymers

Background:

• Transparent conducting films (TCFs) are crucial for electronic devices.
• Existing TCF fabrication methods often involve high temperatures or complex processes.
• Developing scalable and low-cost TCFs for flexible and 3D applications remains a challenge.

Purpose of the Study:

• To formulate low surface tension and low boiling point inks for spray-coating TCFs.
• To demonstrate the viability of spray-coated TCFs on curved surfaces at room temperature.
• To create a novel spherical touch sensor using these TCFs.

Main Methods:

• Formulation of inks with graphene, single-wall carbon nanotubes, and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS).
• Spray-coating technique at room temperature (∼20 °C) to create uniform films.
• Characterization of film morphology, optical transmission, and electrical conductivity.

Main Results:

• Achieved morphologically uniform TCFs (S_q ≈ 48 ± 3 nm) with low surface tension inks.
• Demonstrated conformal coating on three-dimensional curved surfaces.
• Large-area (∼750 cm²) hybrid PEDOT:PSS/graphene films showed 67% UV and 64% near-infrared transmission with conductivity of ∼10⁴ S/m.
• Successfully fabricated a semitransparent spherical touch sensor.

Conclusions:

• Spray-coating of low-surface-tension inks offers a scalable method for producing uniform TCFs.
• The developed TCFs are suitable for flexible and conformable electronic applications.
• This technology enables the creation of innovative interactive devices, such as spherical touch sensors.