[1] Electrocaloric effect in relaxor ferroelectric polymer nanocomposites for solid-state cooling. J. Mater. Chem. A, 8, 16814(2020).

[2] The perovskite structure: A review of its role in ceramic science and technology. Mater. Res. Innov., 4, 3(2016).

[3] PVDF-based ferroelectric polymers in modern flexible electronics. Adv. Electron. Mater., 3, 1600460(2017).

[4] PVDF-based dielectric polymers and their applications in electronic materials. IET Nanodielectrics, 1, 17(2018).

[5] Route towards sustainable smart sensors: Ferroelectric polyvinylidene fluoride-based materials and their integration in flexible electronics. Chem. Soc. Rev., 48, 1787(2019).

[6] Piezoelectric composites for sensor and actuator applications. IEEE Trans. Ultrason. Ferroelectr. Freq. Control, 52, 746(2005).

[7] Dielectric and piezoelectric properties of PVDF/PZT composites: A review. Polym. Eng. Sci., 55, 1589(2015).

[8] . Cellular Solids: Structure and Properties(1999).

[9] . Electrets(1999).

[10] Dielectric barrier discharges: Their history, discharge physics and industrial applications. Plasma Chem. Plasma Process, 23, 1(2003).

[11] Turning polymer foams or polymer-film systems into ferroelectrets: Dielectric barrier discharges in voids. IEEE Trans. Dielectr. Electr. Insul., 18, 34(2011).

[12] Charged cellular polymers with “ferroelectretic” behavior. IEEE Trans. Dielectr. Electr. Insul., 11, 255(2004).

[13] Direct hysteresis measurements on ferroelectret films by means of a modified Sawyer–Tower circuit. J. Appl. Phys., 113, 224106(2013).

[14] Less can be more: Holes in polymers lead to a new paradigm of piezoelectric materials for electret transducers. IEEE Trans. Dielectr. Electr. Insul., 9, 850(2002).

[15] Ferroelectrets: Soft electroactive foams for transducers. Phys. Today, 57, 37(2004).

[16] . The Nano-Micro Interface: Bridging the Micro and Nano Worlds, 303-317(2004).

[17] Microstorms in cellular polymers: A route to soft piezoelectric transducer materials with engineered macroscopic dipoles. Chem. Phys. Chem., 6, 1014(2005).

[18] Patterned piezo-, pyro-, and ferroelectricity of poled polymer electrets. J. Appl. Phys., 108, 011101(2010).

[19] Piezoelectric cellular polymer films: Fabrication, properties and applications. AIMS Mater. Sci., 5, 845-869(2018).

[20] Cellular polymer ferroelectret: A review on their development and their piezoelectric properties. Adv. Polym. Tech., 37, 21686(2018).

[21] Piezoelectrets: A brief introduction. IEEE Sens. J., 21, 22317(2021).

[22] . Electromechanically Active Polymers, 551-560(2016).

[23] . Electromechanically Active Polymers, 561-589(2016).

[24] Effective electromechanical properties of cellular piezoelectret: A review. Acta Mech. Sin., 28, 951-959(2012).

[25] . Electromechanically Active Polymers, 645-659(2016).

[26] Dielectric resonance spectroscopy: A versatile tool in the quest for better piezoelectric polymers. IEEE Trans. Dielectr. Electr. Insul., 10, 842(2003).

[27] Piezoelectric d33 coefficients in foamed and layered polymer piezoelectrets from dynamic mechano-electrical experiments, electro-mechanical resonance spectroscopy and acoustic-transducer measurements. Meas. Sci. Technol., 23, 035604(2012).

[28] . Electromechanically Active Polymers, 591-623(2016).

[29] . Electromechanically Active Polymers, 625-644(2016).

[30] . Electromechanically Active Polymers, 661-668(2016).

[31] Film-type sensor materials PVDF and EMFi in measurement of cardiorespiratory signals — A review. IEEE Sens. J., 12, 439(2012).

[32] Ferroelectret materials and devices for energy harvesting applications. Nano Energy, 57, 118(2019).

[33] Piezoelectrets for wearable energy harvesters and sensors. Nano Energy, 65, 104033(2019).

[34] Mechanical energy harvesting with ferroelectrets. IEEE Electr. Insul. M, 36, 47(2020).

[35] Piezoelectric polymeric foams as flexible energy harvesters: A review. Adv. Energy Sustainability Res., 3, 2200063(2022).

[36] Advances in air-coupled ultrasonic transducers for non-destructive testing. Proc. Mtgs. Acoust., 38, 030003(2019).

[37] Air-coupled ultrasound emerging NDT method. ZfP-Zeitung., 173, 32(2021).

[38] A new principle for the design of condenser electret transducers. J. Acoust. Soc. Am., 63, 1229(1978).

[40] Electrothermomechanical film. Part I. Design and characteristics. J. Macromol. Sci. Chem., A26, 583(1989).

[41] Audio applications of electrothermomechanical film (ETMF). J. Audio Eng. Soc., 38, 364(1990).

[42] Thermal and temporal stability of ferroelectret films made from cellular polypropylene/air composites. Ferroelectrics, 331, 189(2006).

[43] Influence of gas pressure in the voids during charging on the piezoelectricity of ferroelectrets. Appl. Phys. Lett., 92, 052901(2008).

[44] Thermally stable dynamic piezoelectricity in sandwich films of porous and non-porous amorphous fluoropolymer. Appl. Phys. Lett., 79, 1852(2001).

[45] Piezoelectric polyethylene terephthalate (PETP) foams specifically designed and prepared ferroelectret films. Adv. Eng. Mater., 7, 1128(2005).

[46] Polyethylene therephthalate (PETP) foams as ferroelectrets. Proc. 12th Int. Symp. Electrets, 28-30(2005).

[47] Optimized preparation of elastically soft, highly piezoelectric, cellular ferroelectrets from nonvoided poly(ethylene terephthalate) films. Adv. Funct. Mater., 17, 324(2007).

[48] Porous materials and supercritical fluids. Adv. Mater., 15, 1049(2003).

[49] Supercritical carbon dioxide as a green solvent for processing polymer melts: Processing aspects and applications. Prog. Polym. Sci., 31, 19(2006).

[51] Gas diffusion expansion-increased thickness and enhanced electromechanical response of cellular polymer electret films. Proc. 11th Int. Symp. Electrets, 191-194(2002).

[52] Enhancing the cellular structure and the electromechanical response of ferroelectrets — gas diffusion expansion of voided polypropylene films. Annual Report IEEE Conf. Electric Insulation and Dielectric Phenomena, 36-39(2003).

[53] Two-step inflation of cellular polypropylene films: Void-thickness increase and enhanced electromechanical properties. J. Phys. D Appl. Phys., 37, 623(2004).

[54] Piezoelectric d33 coefficient of cellular polypropylene subjected to expansion by pressure treatment. Appl. Phys. Lett., 85, 1226(2004).

[55] The storage and its stability of space charge in poly(ethylene naphthalene-2, 6-dicarboxylate). Sci. China Ser. E, 49, 1(2006).

[56] Cellular polyethylene-naphthalate ferroelectrets: Foaming in supercritical carbon dioxide, structural and electrical preparation, and resulting piezoelectricity. Appl. Phys. Lett., 90, 192908(2007).

[57] Cellular polyethylene-naphthalate films for ferroelectret applications: Foaming, inflation and stretching, assessment of electromechanically relevant structural features. E-Polymers, 8, 43(2008).

[58] Polyethylene-naphthalate (PEN) ferroelectrets: Cellular structure, piezoelectricity and thermal stability. IEEE Trans. Dielectr. Electr. Insul., 17, 1079(2010).

[59] Physical foaming of fluorinated ethylene-propylene (FEP) copolymers in supercritical carbon dioxide: Single film fluoropolymer piezoelectrets. Appl. Phys. A Mater., 90, 615(2008).

[60] Electret properties of cycloolefin copolymers. Electrical insulation and dielectric phenomena. Annual Report IEEE Conf. Electrical Insulation Dielectric Phenomena, 467-470(1997).

[61] Voided cyclo-olefin polymer films: Ferroelectrets with high thermal stability. Proc. 12th Int. Symp. Electrets, 47-50(2005).

[62] Novel heat durable electromechanical film: Processing for electromechanical and electret applications. IEEE Trans. Dielectr. Electr. Insul., 13, 963(2006).

[63] High surface-charge stability of porous polytetrafluoroethylene electret films at room and elevated temperatures. J. Phys. D Appl. Phys., 32, L83(1999).

[64] Influence of thermal treatment on the charge stability of non-porous and porous polytetrafluoroethylene (PTFE) film electrets. Proc. Int. Conf. Solid Dielectric(2010).

[65] Thermal stability of piezoelectricity for porous polytetrafluoroethylene electret film. J. Electrostat., 58, 265(2003).

[66] Influence of porosity on the stability of charge and piezoelectricity for porous polytetrafluoroethylene film electrets. J. Electrostat., 59, 57(2003).

[67] Piezoelectric activity and its stability of polytetrafluoroethylene (PTFE) films. Acta Phys. Sin., 52, 2075(2003).

[68] Porous polytetrafluoroethylene (PTFE) electret films: Porosity and time dependent charging behavior of the free surface. J. Porous Mater., 14, 111(2007).

[69] Charging behavior and thermal stability of porous and non-porous polytetrafluoroethylene (PTFE) electrets. Annual Report IEEE Conf. Electric Insulation and Dielectric Phenomena, 449-452(2007).

[70] Inverse piezoelectricity of porous PTFE films with bipolar space charge. Annual Report IEEE Conf. Electric Insulation and. Dielectric Phenomena, 377-380(2000).

[71] Porous polytetrafluoroethylene space-charge electrets for piezoelectrical applications. IEEE Trans. Dielectr. Electr. Insul., 7, 480(2000).

[72] Porous polytetrafluoroethylene (PTFE) single-film space-charge electrets with high piezoelectric coefficients. 8th Int. Conf. Dielectric Materials, Measurements and Applications (IEE Conf. Publ. No. 473), 380-385(2000).

[73] Piezoelectric properties of nonuniform electrets. J. Electrost., 35, 161(1995).

[74] Double-layer electret transducer. J. Electros., 39, 33(1997).

[75] Preliminary study of multi-layer space-charge electrets with piezoelectric properties from porous and non-porous Teflon films. Proc. 10th Int. Symp. Electrets, 273-276(1999).

[76] Piezoelectricity of porous polytetrafluoroethylene singleand multiple-film electrets containing high charge densities of both polarities. Appl. Phys. A Mater., 70, 5(2000).

[77] Charge stability and piezoelectric properties of porous fluoropolymer space-charge electrets in layer systems. Proc. 4th Int. Conf. Electric Charges in Non-Conductive Materials, 257-260(2001).

[78] Coating of porous polytetrafluoroethylene films with other polymers for electret applications. Annual Report IEEE Conf. Electric Insulation and Dielectric Phenomena, 100-103(2001).

[79] Preparation and characterization of novel piezoelectric and pyroelectric polymer electrets. IEEE Trans. Dielect. Electr. Insul., 7, 578(2000).

[80] Low-dielectric-constant cross-linking polymers: Film electrets with excellent charge stability. Appl. Phys. Lett., 75, 3998(1999).

[81] Breakdown-induced polarization buildup in porous fluoropolymer sandwiches: A thermally stable piezoelectret. J. Appl. Phys., 99, 024102(2006).

[82] Poling dynamics and thermal stability of FEP/ePTFE/FEP sandwiches. IEEE Trans. Dielectr. Electr. Insul., 17, 1056(2010).

[83] Importance of geometry and breakdown field on the piezoelectric d33 coefficient of corona charged ferroelectret sandwiches. IEEE Trans. Dielectr. Electr. Insul., 18, 49(2011).

[84] Piezoelectrets from sandwiched porous polytetrafluoroethylene (ePTFE) films: Influence of porosity and geometry on charging properties. J. Phys. D: Appl. Phys., 44, 105501(2011).

[85] Piezoelectrets from laminated sandwiches of porous polytetrafluoroethylene films and nonporous fluoroethylenepropylene films. J. Appl. Phys., 103, 084111(2008).

[86] Polytetrafluoroethylene piezoelectrets prepared by sintering process. Appl. Phys. A: Mater. Sci. Process., 97, 859(2009).

[87] Quasi-static and dynamic piezoelectric responses of layered polytetrafluoroethylene ferroelectrets. J. Phys. D Appl. Phys., 47, 015501(2014).

[88] Piezoelectrets from thermo-formed bubble structures of fluoropolymerelectret films. IEEE Trans. Dielectr. Electr. Insul., 13, 979(2006).

[89] Three-layer ferroelectrets from perforated Teflon-PTFE films fused between two homogeneous Teflon-FEP films. Annual Report IEEE Conf. Electrical Insulation and Dielectric Phenomena, 453-456(2007).

[90] Template-based fluoroethylenepropylene piezoelectrets with tubular channels for transducer applications. J. Appl. Phys., 106, 014106(2009).

[91] Laminated tubular-channel ferroelectret systems from low-density polyethylene films and from fluoroethylene-propylene copolymer films — A comparison. IEEE Trans. Dielectr. Electr. Insul., 19, 1116(2012).

[92] Piezoelectric-magnetic behavior of ferroelectrets coated with magnetic layer. Appl. Phys. Lett., 119, 241901(2021).

[93] Thermally stable fluorocarbon ferroelectrets with high piezoelectric coefficient. Appl. Phys. A Mater., 84, 139(2006).

[94] Ferroelectrets with improved thermal stability made from fused fluorocarbon layers. J. Appl. Phys., 101, 054114(2007).

[95] Piezoelectric sensor based on electrets thermoforming technology. Proc. Int. Conf. Solid Dielectrics, 1-3(2010). https://doi.org/10.1109/ICSD.2010.5568029

[96] Fabrication of fluoropolymer piezoelectrets by using rigid template: Structure and thermal stability. J. Appl. Phys., 108, 064113(2010).

[97] Polarization and piezoelectricity in polymer films with artificial void structure. Appl. Phys. A Mater., 105, 197(2011).

[98] Fluoroethylenepropylene ferroelectrets with patterned microstructure and high, thermally stable piezoelectricity. Appl. Phys. A Mater., 107, 621(2012).

[99] Threelayer piezoelectrets from fluorinated ethylene-propylene (FEP) copolymer films. Appl. Phys. A Mater., 103, 455(2011).

[100] Polarization from dielectric-barrier discharges in ferroelectrets: Mapping of the electric-field profiles by means of thermalpulse tomography. Appl. Phys. Lett., 97, 072905(2010).

[101] Unipolar ferroelectrets — Following the example of the electret microphone more closely. Annual Reports IEEE Conf. Electrical Insulation and Dielectric Phenomena, 860-862(2014).

[102] Screen printing for producing ferroelectret systems with polymer-electret films and well-defined cavities. Appl. Phys. A Mater., 114, 515(2014).

[103] Piezoelectrets with well-defined cavities produced from 3D-printed ABS structures. Electron. Lett., 51, 2028(2015).

[104] Adding an electroactive response to 3D printed materials: Printing a piezoelectret. Addit. Manuf., 31, 100963(2020).

[105] Hydrophone based on 3D printed polypropylene (PP) piezoelectret. Electron. Lett., 55, 203(2019).

[106] A new route to piezo-polymer transducers: 3D printing of polypropylene ferroelectrets. IEEE Trans. Dielectr. Electr. Insul., 27, 1668(2020).

[107] Low-temperature CO2-assisted assembly of cyclic olefin copolymer ferroelectrets of high piezoelectricity and thermal stability. Macromol. Chem. Phys., 214, 2733(2013).

[108] Piezoelectric polydimethylsiloxane films for MEMS transducers. J. Micromech. Microeng., 22, 015013(2012).

[109] Piezoelectric rubber films for highly sensitive impact measurement. J. Micromech. Microeng., 23, 075009(2013).

[110] Dielectric barrier microdischarges: Mechanism for the charging of cellular piezoelectric polymers. J. Appl. Phys., 91, 5283(2002).

[111] Breakdown threshold of dielectric barrier discharges in ferroelectrets: Where Paschen’s law fails. IEEE Trans. Dielectr. Electr. Insul., 18, 43(2011).

[112] Corona-induced partial discharges, internal charge separation and electromechanical transducer properties in cellular polymer films. Proc. 11th Int. Symp. Electrets, 54-57(2002).

[113] Electrode poling of cellular polypropylene films with short high-voltage pulses. Annual Reports. IEEE Conf. Electrical Insulation and Dielectric Phenomena, 299-302(2002).

[114] Electromechanical response of cellular electret films. Appl. Phys. Lett., 75, 3405(1999).

[115] Modeling the sensor and actuator operations of the electromechanical film EMFi. IEEE 10th Int. Symp. Electrets, IEEE Service Center, 735-738(1999).

[116] Influence of charging parameters on piezoelectricity for cellular polypropylene film electrets. IEEE 12th Int. Symp. Electrets, IEEE Service Center, 39-42(2005).

[117] Polarization hysteresis and piezoelectricity in open-porous fluoropolymer sandwiches. J. Appl. Phys., 102, 044109(2007).

[118] Barrier discharges in cellular polypropylene ferroelectrets: How do they influence the electromechanical properties?. J. Appl. Phys., 107, 104112(2007).

[119] Spectroscopic study of dielectric barrier discharges in cellular polypropylene ferroelectrets. Appl. Phys. Lett., 91, 132905(2007).

[120] Light Emission from Cellular Polypropylene Ferroelectrets under High Electric Fields and Its Correlation with Piezoelectricity. IEEE 13th Int. Sym. Electrets ISE 13, C205-C205(2008). https://doi.org/10.1109/ISE.2008.4814078

[121] Discharge patterns in three-layer ferroelectret systems with perforated polymer films. IEEE 13th Int. Symp. Electrets ISE 13, C202-C202(2008). https://doi.org/10.1109/ise.2008.4814075

[122] Dielectric barrier discharges in multi-layer polymer ferroelectrets. Annual Reports IEEE Conf. Electrical Insulation and Dielectric Phenomena, 142-145(2009). https://doi.org/10.1109/CEIDP.2009.5377827

[123] In-situ acoustical investigation of the polarization build-up in cellular polypropylene ferroelectrets. IEEE Trans. Dielectr. Electr. Insul., 17, 1043(2010).

[124] Piezoelectricity and ferroelectricity of cellular polypropylene electrets films characterized by piezoresponse force microscopy. J. Appl. Phys., 116, 066820(2014).

[125] Polarization-electric field hysteresis of ferroelectric PVDF films: Comparison of different measurement regimes. Rev. Sci. Instrum., 79, 106103(2008).

[126] Temporal evolution of the re-breakdown voltage in small gaps from nanoseconds to milliseconds. Appl. Phys. Lett., 102, 012904(2013).

[127] Effective polarization fatigue from repeated dielectric barrierdischarges in cellular polypropylene ferroelectrets. Appl. Phys. Lett., 93, 152902(2008).

[128] Beneficial and detrimental fatigue effects of dielectric barrier discharges on the piezoelectricity of polypropylene ferroelectrets. J. Appl. Phys., 110, 024108(2011).

[129] Fatigue and recovery of cellular-polypropylene piezoelectrets during and after dielectric-barrier discharges. Annual Reports IEEE Conf. Electrical Insulation and Dielectric Phenomena, 591-594(2013).

[130] Charging of cellular space-charge electret films in various gas atmospheres. Annual Reports IEEE Conf. Electrical Insulation and Dielectric Phenomena, 24-27(2001).

[131] Understanding the role of the gas in the voids during corona charging of cellular electret films — a way to enhance their piezoelectricity. J. Phys. D Appl. Phys., 34, 2482(2001).

[132] The piezoelectricity of heatexpanded PP cellular electret. Acta Phys. Sin., 54, 402(2005).

[133] Penetration of sulfur hexafluoride into cellular polypropylene films and its effect on the electric charging and electromechanical response of ferroelectrets. J. Phys. D Appl. Phys., 38, 649(2005).

[134] Significant enhancement of the charging efficiency in the cavities of ferroelectrets through gas exchange during charging. Appl. Phys. Lett., 109, 222903(2016).

[135] . Dielectric Phenomena in High Voltage Engineering(1915, 1920, and 1929).

[136] Temperature dependence of quasi-ferroelectric hysteresis in a model ferroelectret system. Annual Reports IEEE Conf. Electrical Insulation and Dielectric Phenomena, 644-647(2015).

[137] Thermal poling of ferroelectrets: How does the gas temperature influence dielectric barrier discharges in cavities?. Appl. Phys. Lett., 108, 252901(2016).

[138] Alternating current-generated plasma discharges for the controlled direct current charging of ferroelectrets. J. Appl. Phys., 114, 104101(2013).

[139] Trench-filled cellular parylene electret for piezoelectric transducer. Appl. Phys. Lett., 100, 262901(2012).

[140] All-polymer soft-X-ray-charged piezoelectret with embedded PEDOT electrode. MEMS, 865-868(2013).

[141] A matter of attraction: Electric charges localised on dielectric polymers enable electromechanical transduction. Annual Reports IEEE Conf. Electrical Insulation and Dielectric Phenomena, 1-10(2014).

[143] Composite rubber electret with piezoelectric 31 and 33 modes for elastically electromechanical sensors. IEEE Sens.(2015). https://doi.org/10.1109/ICSENS.2015.7370287

[144] Vibration-based energy harvesting with piezoelectrets having high d31 activity. Appl. Phys. Lett., 108, 193903(2016).

[145] Ferroelectret nanogenerator with large transverse piezoelectric activity. Nano Energy, 50, 52(2018).

[146] Polarization and hysteresis in tubular-channel fluoroethylenepropylene-copolymer ferroelectrets. Ferroelectrics, 472, 100(2014).

[147] Charge-spring model for predicting the piezoelectric response of dielectric materials: Considering tetragonality extends validity to ferroelectric perovskites. Annual Reports IEEE Conf. Electrical Insulation and Dielectric Phenomena, 81-84(2016).

[148] Controlled inflation of voids in cellular polymer ferroelectrets: Optimizing electromechanical transducer properties. Appl. Phys. Lett., 84, 392(2004).

[149] Influence of heat treatment temperature after the pressure expansion on the electromechanical properties of cellular polypropylene electret. Acta Phys. Sin., 55, 2578(2006).

[150] Cellular polypropylene foam films as DC voltage insulation and as piezoelectrets—A comparison. IEEE Trans. Dielectr. Electr. Insul., 25, 829(2018).

[151] Elastic properties of highly anisotropic thin poly(propylene) foams. Mater. Lett., 58, 2815(2004).

[152] Modeling electro-mechanical properties of layered electrets: Application of the finite-element method. J. Electrostat., 63, 21(2005).

[153] Dielectric resonance spectroscopy of piezoelectrets with tubular channels: Channel dimensions control resonances. Proc. Int. Conf. Solid Dielectric(2010).

[154] Fluoropolymer piezoelectrets with tubular channels: Resonance behavior controlled by channel geometry. Appl. Phys. A Mater., 107, 965(2012).

[155] Template-based fluoropolymer ferroelectrets with multiple layers of tubular channels. Annual Reports IEEE Conf. Electrical Insulation and Dielectric Phenomena(2010).

[156] Fluoroethylenepropylene ferroelectrets with superimposed multi-layer tubular void channels. Annual Reports IEEE Conf. Electrical Insulation and Dielectric Phenomena(2011).

[157] Charging properties and time-temperature stability of innovative polymeric cellular ferroelectrets. IEEE Trans. Dielectr. Electr. Insul., 14, 238(2007).

[158] Thermal instability of electromechanical films of cellular polypropylene. IEEE Trans. Dielectr. Electr. Insul., 12, 768(2005).

[159] Ultraviolet-induced discharge currents and reduction of piezoelectric coefficient in cellular polypropylene films. Appl. Phys. Lett., 82, 254(2003).

[160] Electret properties of polyethylene and polytetrafluoroethylene films with chemically modified surface. IEEE Trans. Dielectr. Electr. Insul., 18, 8(2011).

[161] Stabilization of positive charge on polytetrafluoroethylene electret films treated with titaniumtetrachloride vapor. Appl. Phys. Lett., 98, 122901(2011).

[162] Enhanced electret charge stability on polyethylene films treated with titaniumtetrachloride vapor. IEEE Trans. Dielectr. Electr. Insul., 19, 1305(2012).

[163] Chemical and physical surface modification of PTFE films — an approach to produce stable electrets. Appl. Phys. A Mater., 107, 589(2012).

[164] Higher stabilities of positive and negative charge on tetrafluoroethylene-hexafluoropropylene copolymer (FEP) electrets treated with titanium-tetrachloride vapor. Appl. Phys. A Mater., 112, 283(2013).

[165] Influence of charge density on the trap-energy spectrum in fluoroethylenepropylene copolymer films with chemically modified surfaces. IEEE Trans. Dielectr. Electr. Insul., 25, 840(2018).

[166] Chemical modification with orthophosphoric acid enhances surface-charge stability on polypropylene electrets. Appl. Phys. Lett., 110, 192901(2017).

[167] The influence of orthophosphoric-acid surface modification on charge-storage enhancement in polypropylene electrets. J. Appl. Phys., 128, 034102(2020).

[168] Influence of fluorination on piezoelectric properties of cellular polypropylene ferroelectrets. J. Phys. D Appl. Phys., 42, 015418(2009).

[169] Significantly improved piezoelectric thermal stability of cellular polypropylene films by high pressure fluorination and post-treatments. J. Appl. Phys., 111, 024111(2012).

[170] Treatment with orthophosphoric acid enhances the thermal stability of the piezoelectricity in low-density polyethylene ferroelectrets. J. Appl. Phys., 111, 124105(2012).

[171] Template-based fluoroethylenepropylene ferroelectrets with enhanced thermal stability of piezoelectricity. J. Appl. Phys., 124, 174105(2018).

[172] Air-borne ultrasonic transducers based on cross-linked polypropylene ferro/piezoelectrets. IEEE Sens. J., 22, 14806-14814(2022).

[173] Using thin-film piezoelectret to detect tactile and slip signals for restoring sensation of prosthetic hands. Conf. Proc. IEEE Engineering in Medicine and Biology Society, 2565-2568(2014).

[174] A piezoelectretbased approach for touching and slipping detection in robotic hands. 2015 IEEE Int. Conf. Cyber Technology in Automation, Control, and Intelligent Systems (CYBER), 918-921(2015).

[175] Flexible film-transducers based on polypropylene piezoelectrets: Fabrication, properties, and applications in wearable devices. Sensor. Actuat. A Phys., 256, 35(2017).

[176] Fabrication, structure characterization, and performance testing of piezoelectret-film sensors for recording body motion. IEEE Sens. J., 18, 401(2018).

[177] A novel motion recognition method based on force-myography of dynamic muscle contractions. Front. Neurosci., 15, 783539(2022).

[178] Cellular polypropylene piezoelectret for human body energy harvesting and health monitoring. Adv. Funct. Mater., 25, 4788(2015).

[179] Human pulse diagnosis for medical assessments using a wearable piezoelectret sensing system. Adv. Funct. Mater., 28, 1803413(2018).

[180] Human pulses reveal health conditions by a piezoelectret sensor via the approximate entropy analysis. Nano Energy, 58, 528(2019).

[181] Wrist pulse recording with a wearable piezoresistorpiezoelectret compound sensing system and its applications in health monitoring. IEEE Sens. J., 21, 20921(2021).

[182] Dielectric elastomer and ferroelectret films combined in a single device: How do they reinforce each other?. Appl. Phys. A Mater., 107, 583(2012).

[183] Self-organized minimumenergy structures for dielectric elastomer actuators. Appl. Phys. A Mater., 85, 141(2006).

[184] Finite element modelling of dielectric elastomer minimum energy structures. Appl. Phys. A Mater., 94, 507(2009).

[185] Energy minimization for selforganized structure formation and actuation. Appl. Phys. Lett., 90, 081916(2007).

[186] Piezo-electret vibration sensors designed for acoustic-electric guitars. IEEE Trans. Dielectr. Electr. Insul., 27, 1675(2020).

[187] The bow on a string: Bow vibrations detected with ferroelectret sensors. Acta Acust. United Ac., 104, 315(2018).

[188] Piezoelectret sensors detect geometry-related modifications of the acoustical signatures from partial discharges in an electrical equipment chamber. Annual Reports IEEE Conf. Electrical Insulation and Dielectric Phenomena, 108-111(2012).