Uniaxially stretched poly(l-lactide) (US-PLA) films display shear piezoelectric properties of interests for smart applications. However, the measurement of these properties is quite challenging and a simple technique based on bimorph cantilevers is here used. This technique is validated with commercial piezoelectric poly(vinylidene fluoride) (PVDF) films. A piezoelectric coefficient d₃₁ close to 19 pm/V is then obtained with a precision close to 5% and a good accuracy to expected values. For US-PLA films made by extrusion—machine-direction orientation, shear piezoelectric coefficients d₁₄ up to 5.9 pm/V are found. Relevant trends can be captured but a low precision on d₁₄, close to 10%, is highlighted. This behavior is probably related to film thickness heterogeneities arising from the extrusion processing at the laboratory scale. Piezoelectric voltage coefficients (g₁₄) and electromechanical coupling coefficients could be also easily obtained with additional measurements of the dielectric permittivity and mechanical compliance. Outstanding g₁₄ coefficients up to 320 mV.m/N are confirmed for US-PLA films with a precision close to 20%. The bimorph cantilever technique consequently represents a simple and reliable technique to evaluate piezoelectric properties of soft materials, in particular shear piezoelectric properties of US-PLA films for future developments and optimizations at the pilot scale.

中文翻译：

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双压电晶片悬臂技术对挤出和定向聚（l-丙交酯）薄膜剪切压电系数的评价

单轴拉伸聚（l-丙交酯）（US-PLA）薄膜显示出对智能应用感兴趣的剪切压电特性。然而，这些特性的测量非常具有挑战性，这里使用了一种基于双压电晶片悬臂梁的简单技术。该技术已通过商用压电聚偏二氟乙烯 (PVDF) 薄膜进行验证。然后获得接近19pm/V的压电系数d ₃₁，其精确度接近5％并且与预期值具有良好的准确度。对于通过挤出-机器方向取向制成的 US-PLA 薄膜，发现剪切压电系数d ₁₄高达 5.9 pm/V。可以捕获相关趋势，但d _{14的精度较低}, 接近 10%, 被突出显示。这种行为可能与实验室规模的挤出加工产生的薄膜厚度不均匀性有关。压电电压系数 ( g ₁₄ ) 和机电耦合系数也可以通过介电常数和机械顺应性的额外测量轻松获得。US-PLA 薄膜的g ₁₄系数高达 320 mV.m /N，精度接近 20%。因此，双压电晶片悬臂梁技术代表了一种简单可靠的技术，用于评估软材料的压电特性，特别是 US-PLA 薄膜的剪切压电特性，用于未来的开发和中试规模的优化。