Design and characterization of thin-film electroadhesion technologies fabricated via digital printing techniques

Electroadhesion is physical phenomenon that is exploited by a class of capacitive electrostatic transduction technologies, referred to as Electro-Adhesion Devices (EADs), enabling controllable and reversible adhesion between surfaces through the application of electric fields. EADs are ideal candidates for autonomous robotic systems, industrial logistics, and space applications, easily complementing conventional grippers, and enhancing the overall load capacity through hybrid systems that combine the strengths of multiple technologies. Recent advancements in flexible printed electronics have substantially enabled the design and development of lightweight and cost-effective electrostatic transducers. At the same time, materials design plays a crucial role in enhancing the dielectric properties of the functional layers in EADs, addressing limitations in the achievable electroadhesion forces. This doctoral research explores the design, fabrication, and characterization of electroadhesion devices developed by using digital printing techniques and polymer-based dielectric materials, aiming to advance both scientific understanding and industrial applicability. Polyimide (PI), polyethylene-terephthalate (PET), and polyethylene-naphthalate (PEN) films were assessed as functional layers for electrostatic clutches through the characterization of their dielectric strength, relative permittivity, thickness, friction coefficient, and electrostatic shear stress (ESS). Custom experimental setups were developed to this aim, leading to the identification of PEN Kaladex2000 and PI Kapton50HN by Dupont as the most promising materials, for their high dielectric strength, low friction, and ESS values of 180kPa and 170kPa achieved at 157kV/mm and 199kV/mm, respectively. Remarkable shear stress amplification ratio was recorded for them, surpassing values previously reported in the literature. The experimental ESS curves measured for the designed electrostatic clutches were predicted by a simplified analytical model accounting for the effect of an interfacial air gap, demonstrating good accuracy, especially for PEN Kaladex 2000 in the electric field range from 10 to 100kV/mm.