Energy micro-GENEration with PIezoelectric biobased polymers – GENEPI

The GENEPI project relied on an integrated experimental and theoretical approach to establish relationships between polymer processing conditions and resulting piezoelectric properties. The work combined process development, multi-scale characterization and physical modelling to address key scientific challenges associated with biobased piezoelectric polymers.

A first step consisted in developing a reliable and reproducible manufacturing process for oriented PLA films using industrial extrusion followed by controlled uniaxial stretching (Machine Direction Orientation – MDO). This approach induces a specific molecular organization responsible for shear piezoelectricity without requiring electrical poling. Processing parameters such as stretching temperature, draw ratio, strain rate and post-processing thermal treatments were systematically investigated to control material structuration. In parallel, advanced experimental tools were developed to accurately characterize molecular orientation and shear piezoelectric coefficients. These methodologies significantly improved measurement reliability and reduced uncertainties, enabling the establishment of robust predictive relationships.

The project also integrated modelling approaches to describe the respective contributions of the different structural phases of the polymer (amorphous phase, mesophase and crystalline phases) to the overall piezoelectric response. These models provided key insights into the influence of processing conditions on electromechanical properties and guided optimization strategies. Finally, several exploratory approaches were investigated to enhance material performance, including the use of functional additives, controlled crystallization and the development of porous and architectured structures enabling pseudo-ferroelectric behaviour.

This multidisciplinary approach enabled a strong convergence between fundamental understanding and industrial feasibility, paving the way for future applications in sensing, actuation and energy harvesting.

The GENEPI project enabled major scientific and technological breakthroughs, positioning biobased polymers as credible alternatives for piezoelectric applications.

A first key achievement is the development of a robust, reproducible and scalable manufacturing process for oriented PLA films with high piezoelectric performances. The use of extrusion–MDO processes, operated close to the glass transition temperature, enabled precise control of deformation and molecular structuration, demonstrating the feasibility of large-scale production of functional bio-based materials.

A major scientific breakthrough was achieved in the understanding of PLA piezoelectricity. Thanks to dedicated experimental tools and multiphase predictive models, it was demonstrated that the piezoelectric response does not solely originate from crystalline phases but also significantly involves the oriented amorphous phase. This contribution, estimated at around 20% of the overall performance, represents a key advance for predicting and optimizing material behaviour. These developments led to state-of-the-art piezoelectric performances for PLA (d14 > 13 pC/N), exceeding previously reported values, while maintaining key advantages such as transparency, high thermal stability and the absence of electrical poling.

Beyond dense films, the project opened new research directions through the development of porous and architectured PLA-based structures exhibiting pseudo-ferroelectric behaviour and high piezoelectric coefficients. These results introduce the emerging concept of “meta-piezoelectric” materials, where functionality arises from both material composition and internal architecture. Finally, several application-oriented demonstrations highlighted the potential of piezoelectric PLA for energy harvesting, self-powered sensing and environmental applications such as pollutant degradation through piezocatalysis.

Overall, GENEPI establishes the scientific and technological foundations for a new generation of sustainable piezoelectric transducers compatible with flexible electronics and autonomous energy systems.

The results of the GENEPI project open major scientific, technological and industrial perspectives for the development of sustainable piezoelectric materials.

From a scientific perspective, the project revealed new mechanisms governing the piezoelectric behaviour of bio-based polymers, particularly the role of structural phases and their dependence on processing conditions. These findings open new research directions, including the study of amorphous and crystalline phase interactions, dielectric and viscoelastic relaxations and advanced multi-scale structuration strategies aimed at developing high-performance electroactive polymers without critical or fluorinated materials.

Beyond academic outcomes, the achieved progress also enables the development of industrial demonstrators of PLA-based piezoelectric films and transducers using processes compatible with existing plastic processing lines. This continuity between fundamental research and industrial implementation is a key driver for technology transfer towards applications such as energy harvesting, self-powered sensors, flexible electronics, biomedical devices and environmental remediation through piezocatalysis. Beyond academic outcomes, the project highlights the potential emergence of a new generation of low-carbon, biobased piezoelectric transducers, relying on recyclable materials and energy-efficient processes. These advances pave the way for the creation of a start-up dedicated to “zero-carbon” piezoelectric devices addressing growing needs in IoT, smart mobility and sustainable infrastructures.

The collaborations initiated during the project have already led to new national and European projects on electroactive polymers, flexible transducers and hybrid energy harvesting systems. GENEPI thus contributes to structuring a research community at the interface of polymer science, flexible electronics and energy transition, positioning IMT Nord Europe as a key player in the emerging field of sustainable electroactive materials.

Piezoelectric materials represent strategic elements for sensors and energy harvesters with multiple applications, in particular with the emergence of self-powered IoT devices. However, new concepts are required to tackle economic and environmental issues regarding actual lead-based piezoelectric ceramics without compromising final performances. The GENEPI project consequently investigates the spontaneous shear piezoelectricity of poly(L-Lactide) (PLA) as an ideal alternative with many positive benefits. An industrially-relevant and solvent-free extrusion-orientation (MDO) fabrication process is currently under development at IMT Lille Douai to open a straightforward fabrication of PLA-based sensors / harvesters but several scientific challenges need to be overcome to get a full expertise on these technologies and enable faster developments. In this context, the first scientific objective of GENEPI project is to improve the knowledge on shear piezoelectric properties of PLA, in particular on process – structures – properties relationships and the use of (meth)acrylic block copolymers as blending partners to develop high-performance shear piezoelectric films at the laboratory scale. The second scientific objective of the GENEPI project is to convert the peculiar piezoelectricity of PLA into a conventional ferroelectric behavior in order to boost piezoelectric properties of PLA beyond the theoretical limit with electromechanical responses in practical mechanical modes for sensing / actuation / harvesting operations. This challenging task will explore several concepts (high-temperature ferroelectricity of PLA, pseudo-ferroelectricity of nanostructured PLA-based blends and electric field-assisted crystallization of PLA) to reveal long-term research strategies.