Piezopermittivity refers to the reversible change of the electric permittivity (the main material property that describes the dielectric behavior) with the elastic strain. This paper addresses the emerging field of piezopermittivity, which provides the basis for capacitance-based strain/stress sensing, including self-sensing in case of structural materials. Piezopermittivity differs from piezoresistivity, which allows resistance-based strain/stress sensing. It also differs from the direct piezoelectric effect, which does not require the permittivity to change. In order to establish piezopermittivity, this paper presents the piezopermittivity theory, sensing methodology, and piezopermittivity-related materials science. Piezopermittivity stems from the effect of strain on the microstructure, which affects the permittivity. It is exhibited by electrical conductors (metals, carbons, and carbon fiber polymer-matrix and carbon-matrix composite) and nonconductors (perovskite ceramic and 3D-printed polymer), which are comparably effective for capacitance-based sensing, as shown at frequencies ≤2 kHz. All materials are unpoled. Poling of the perovskite ceramic does not alter the piezopermittivity behavior. The magnitude of the fractional change in permittivity much exceeds the strain magnitude, as expected for piezopermittivity. The sensing effectiveness, as described by the fractional change in permittivity per unit strain, is positive for positive piezopermittivity and negative for negative piezopermittivity. The majority of the materials exhibit positive piezopermittivity. The sensing effectiveness is +1.99×10³ and -4.81×10² for uncoated and nickel-coated carbon fibers, respectively. The value for the uncoated carbon fiber is close to the value of +1.21×10³ for a perovskite ceramic. For a 3D-printed polymer, the value is -2.87×10⁶ in the direction perpendicular to the printed layers. Capacitance-based sensing is advantageous to the widely reported resistance-based sensing in that it does not require intimate contact of the electrodes with the specimen. The measurement of the capacitance of a conductive material using an LCR meter requires a dielectric film between the electrode and specimen.

介电常数是指介电常数（描述介电行为的主要材料属性）随弹性应变的可逆变化。本文讨论了压电介电常数的新兴领域，它为基于电容的应变/应力传感提供了基础，包括结构材料情况下的自传感。压电电容率与压阻率不同，压阻率允许基于电阻的应变/应力传感。它也不同于直接压电效应，后者不需要改变介电常数。为了建立压电介电常数，本文介绍了压电介电常数理论、传感方法和与压电介电常数相关的材料科学。压电介电常数源于应变对微观结构的影响，从而影响介电常数。它表现为电导体（金属、碳和碳纤维聚合物基体和碳基复合材料）和非导体（钙钛矿陶瓷和 3D 打印聚合物），它们对于基于电容的传感相当有效，如频率≤ 2 千赫。所有材料均未极化。钙钛矿陶瓷的极化不会改变压电介电常数行为。正如压电电容率所预期的那样，介电常数的分数变化幅度远远超过应变幅度。如由每单位应变的介电常数的分数变化所描述的，感测效率对于正压介电常数为正，对于负压介电常数为负。大多数材料表现出正的压电介电常数。感应效率+1.99×10 和碳纤维聚合物基质和碳基质复合材料）和非导体（钙钛矿陶瓷和 3D 打印聚合物），它们对于基于电容的传感相当有效，如频率≤2 kHz 所示。所有材料均未极化。钙钛矿陶瓷的极化不会改变压电介电常数行为。正如压电介电常数所预期的那样，介电常数的分数变化幅度远远超过应变幅度。如由每单位应变的介电常数的分数变化所描述的，感测效率对于正压介电常数为正，对于负压介电常数为负。大多数材料表现出正的压电介电常数。感应效率+1.99×10 和碳纤维聚合物基质和碳基质复合材料）和非导体（钙钛矿陶瓷和 3D 打印聚合物），它们对于基于电容的传感相当有效，如频率≤2 kHz 所示。所有材料均未极化。钙钛矿陶瓷的极化不会改变压电介电常数行为。正如压电电容率所预期的那样，介电常数的分数变化幅度远远超过应变幅度。如由每单位应变的介电常数的分数变化所描述的，感测效率对于正压介电常数为正，对于负压介电常数为负。大多数材料表现出正的压电介电常数。感应效率+1.99×10 这对于基于电容的感测相当有效，如频率 ≤ 2 kHz 所示。所有材料均未极化。钙钛矿陶瓷的极化不会改变压电介电常数行为。正如压电电容率所预期的那样，介电常数的分数变化幅度远远超过应变幅度。如由每单位应变的介电常数的分数变化所描述的，感测效率对于正压介电常数为正，对于负压介电常数为负。大多数材料表现出正的压电介电常数。感应效率+1.99×10 这对于基于电容的感测相当有效，如频率 ≤ 2 kHz 所示。所有材料均未极化。钙钛矿陶瓷的极化不会改变压电介电常数行为。正如压电电容率所预期的那样，介电常数的分数变化幅度远远超过应变幅度。如由每单位应变的介电常数的分数变化所描述的，感测效率对于正压介电常数为正，对于负压介电常数为负。大多数材料表现出正的压电介电常数。感应效率+1.99×10 正如压电电容率所预期的那样，介电常数的分数变化幅度远远超过应变幅度。如由每单位应变的介电常数的分数变化所描述的，感测效率对于正压介电常数为正，对于负压介电常数为负。大多数材料表现出正的压电介电常数。感应效率+1.99×10 正如压电介电常数所预期的那样，介电常数的分数变化幅度远远超过应变幅度。如由每单位应变的介电常数的分数变化所描述的，感测效率对于正压介电常数为正，对于负压介电常数为负。大多数材料表现出正的压电介电常数。感应效率+1.99×10³和 -4.81×10 ^{2 分别}用于未涂层和镍涂层碳纤维。未涂覆碳纤维的值接近钙钛矿陶瓷的+1.21×10 ³值。对于 3D 打印的聚合物，在垂直于打印层的方向上该值为 -2.87×10 ⁶。基于电容的传感优于广泛报道的基于电阻的传感，因为它不需要电极与样品的密切接触。使用 LCR 计测量导电材料的电容需要在电极和样品之间有一层介电膜。