LPPI

Stimulable materials

People in charge: Frederic Vidal - Pierre-Henri Aubert

Functional polymer materials made from both RIPs and electronic conductive polymers have as their main application electrostimulable devices (inducing a change in color or volume/shape when an electrical potential is applied).

 

In this instance, an electronic conductive polymer, the PEDOT is interpenetrated (1 to 30 µm) beneath the surface of a thin ionic conductive RIP membrane containing the ions necessary for the redox process to make the device functioning. The interpenetrated architecture of these materials has solved almost all limitations presented by such systems in the literature (delamination, cyclability, open-air operating issues, need for backing electrodes…).

 

 

Depending on the amount of PCE incorporated, changes in volume or shape (actuator, PEDOT > 7%) or color (electrochromic, PEDOT < 0.5%) are observed as a result of electrical stimulation.

Microactuators have been made by microsystems-specific processes. This work is among the most successful in terms of actuation frequency (>100Hz), of dimensions (the smallest published to date), and a liquid medium actuation possibility, in open air and even under a moderate vacuum (10-5 mbar) opening new possibilities in the field of microsystems, microfluidic and biomedical.

 

                                  

Pictures of micro-actuators obtained by scanning electron microscopy: at rest and under actuation (rE = ±3V) under moderate vacuum (10-5 mbar)

The shrinking has also significantly reduced the actuation voltage of dielectric actuators, generally higher than kV. For this purpose, specific electrodes have been developed in the form of films of nanometre thickness, consisting of a 2D interconnected network of carbon nanotubes (NTC) in a polymer monolayer pi-conjugated made by the Langmuir-Blodgett technique. These stretchable electrodes remain conductive up to 100% deformation and allow the development of ultrathin actuators (~1 µm) which generate a linear deformation of 4% for an applied voltage of only 100V. (X.Ji et all 2018 doi :10.2016/j.snb.2018.01.145)

 

The large variety of pi-conjugate structures offers a wide range of accessible colors. Thus, alternating copolymers type D-A-D cyan, magenta and yellow have been developed. These polymers, along with other polymers with achromatic redox states, have been integrated as thin films into electrochromic cells. The devices have evaluated their stability in electrochemical ageing.

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