Alessandra Zucca

Roll to roll processing of ultraconformable conducting polymer nanosheets

Thin and compliant conductive materials and electronic devices that are able to stand as free-standing membranes or to conform to surfaces are relevant for the development of human-device interfaces and unperceivable skin-contact personal health monitoring systems. In this work, a roll-to-roll (R2R) process for the preparation of conductive polymer nanosheets on large areas has been developed in view to move such technology towards real-world applications. R2R conductive nanosheets are obtained as free-standing structures through release from a temporary substrate and then transferred in conformal contact with any target surface with arbitrary shape, curvature and surface topography (including biological tissue such as skin). A specific high-conductivity formulation of PEDOT:PSS has been optimized for skin-contact applications, by making use of butylene glycol (BG) as a dopant: a dermatologically approved ingredient. The R2R nanosheets were tested as unperceivable surface electromyography electrodes able to record muscle-electrical activity. The present R2R process has advantageous properties such as continuous, high throughput printing on large area rolls, cost-effectiveness, speed of execution and use of industry-ready/mass-scale manufacturing technology.

Tattoo conductive polymer nanosheets for skin-contact applications.

Conductive tattoo nanosheets are fabricated on top of decal transfer paper and transferred on target surfaces as temporary transfer tattoos. Circuits are patterned with ink-jet printing. Tattoo nanosheets are envisioned as unperceivable human-device interfaces because of conformal adhesion to complex surfaces including skin. They are tested as dry electrodes for surface electromyography (sEMG), which permits the control of a robotic hand.

Patterned Free-Standing Conductive Nanofilms for Ultraconformable Circuits and Smart Interfaces

A process is presented for the fabrication of patterned ultrathin free-standing conductive nanofilms based on an all-polymer bilayer structure composed of poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) and poly(lactic acid) (PEDOT:PSS/PLA). Based on the strategy recently introduced by our group for producing large area free-standing nanofilms of conductive polymers with ultrahigh conformability, here an inkjet subtractive patterning technique was used, with localized overoxidation of PEDOT:PSS that caused the local irreversible loss of electrical conductivity. Different pattern geometries (e.g., interdigitated electrodes with various spacing, etc.) were tested for validating the proposed process. The fabrication of individually addressable microelectrodes and simple circuits on nanofilm having thickness ∼250 nm has been demonstrated. Using this strategy, mechanically robust, conformable ultrathin polymer films could be produced that can be released in water as free-standing nanofilms and/or collected on surfaces with arbitrary shapes, topography and compliance, including human skin. The patterned bilayer nanofilms were characterized as regards their morphology, thickness, topography, conductivity, and electrochemical behavior. In addition, the electrochemical switching of surface properties has been evaluated by means of contact angle measurements. These novel conductive materials can find use as ultrathin, conformable electronic devices and in many bioelectrical applications. Moreover, by exploiting the electrochemical properties of conducting polymers, they can act as responsive smart biointerfaces and in the field of conformable bioelectronics, for example, as electrodes on tissues or smart conductive substrates for cell culturing and stimulation.