@article{WarringtonBeaumontHorikoshietal.2019, author = {Warrington, Nicole and Beaumont, Robin and Horikoshi, Momoko and Day, Felix R. and Helgeland, {\O}yvind and Laurin, Charles and Bacelis, Jonas and Peng, Shouneng and Hao, Ke and Feenstra, Bjarke and Wood, Andrew R. and Mahajan, Anubha and Tyrrell, Jessica and Robertson, Neil R. and Rayner, N. William and Qiao, Zhen and Moen, Gunn-Helen and Vaudel, Marc and Marsit, Carmen and Chen, Jia and Nodzenski, Michael and Schnurr, Theresia M. and Zafarmand, Mohammad Hadi and Bradfield, Jonathan P. and Grarup, Niels and Kooijman, Marjolein N. and Li-Gao, Ruifang and Geller, Frank and Ahluwalia, Tarunveer Singh and Paternoster, Lavinia and Rueedi, Rico and Huikari, Ville and Hottenga, Jouke-Jan and Lyytik{\"a}inen, Leo-Pekka and Cavadino, Alana and Metrustry, Sarah and Cousminer, Diana L. and Wu, Ying and Thiering, Elisabeth Paula and Wang, Carol A. and Have, Christian Theil and Vilor-Tejedor, Natalia and Joshi, Peter K. and Painter, Jodie N. and Ntalla, Ioanna and Myhre, Ronny and Pitk{\"a}nen, Niina and van Leeuwen, Elisabeth M. and Joro, Raimo and Lagou, Vasiliki and Richmond, Rebecca C. and Espinosa, Ana and Barton, Sheila J. and Inskip, Hazel M. and Holloway, John W. and Santa-Marina, Loreto and Estivill, Xavier and Ang, Wei and Marsh, Julie A. and Reichetzeder, Christoph and Marullo, Letizia and Hocher, Berthold and Lunetta, Kathryn L. and Murabito, Joanne M. and Relton, Caroline L. and Kogevinas, Manolis and Chatzi, Leda and Allard, Catherine and Bouchard, Luigi and Hivert, Marie-France and Zhang, Ge and Muglia, Louis J. and Heikkinen, Jani and Morgen, Camilla S. and van Kampen, Antoine H. C. and van Schaik, Barbera D. C. and Mentch, Frank D. and Langenberg, Claudia and Scott, Robert A. and Zhao, Jing Hua and Hemani, Gibran and Ring, Susan M. and Bennett, Amanda J. and Gaulton, Kyle J. and Fernandez-Tajes, Juan and van Zuydam, Natalie R. and Medina-Gomez, Carolina and de Haan, Hugoline G. and Rosendaal, Frits R. and Kutalik, Zolt{\´a}n and Marques-Vidal, Pedro and Das, Shikta and Willemsen, Gonneke and Mbarek, Hamdi and M{\"u}ller-Nurasyid, Martina and Standl, Marie and Appel, Emil V. R. and Fonvig, Cilius Esmann and Trier, Caecilie and van Beijsterveldt, Catharina E. M. and Murcia, Mario and Bustamante, Mariona and Bon{\`a}s-Guarch, S{\´i}lvia and Hougaard, David M. and Mercader, Josep M. and Linneberg, Allan and Schraut, Katharina E. and Lind, Penelope A. and Medland, Sarah Elizabeth and Shields, Beverley M. and Knight, Bridget A. and Chai, Jin-Fang and Panoutsopoulou, Kalliope and Bartels, Meike and S{\´a}nchez, Friman and Stokholm, Jakob and Torrents, David and Vinding, Rebecca K. and Willems, Sara M. and Atalay, Mustafa and Chawes, Bo L. and Kovacs, Peter and Prokopenko, Inga and Tuke, Marcus A. and Yaghootkar, Hanieh and Ruth, Katherine S. and Jones, Samuel E. and Loh, Po-Ru and Murray, Anna and Weedon, Michael N. and T{\"o}njes, Anke and Stumvoll, Michael and Michaelsen, Kim Fleischer and Eloranta, Aino-Maija and Lakka, Timo A. and van Duijn, Cornelia M. and Kiess, Wieland and Koerner, Antje and Niinikoski, Harri and Pahkala, Katja and Raitakari, Olli T. and Jacobsson, Bo and Zeggini, Eleftheria and Dedoussis, George V. and Teo, Yik-Ying and Saw, Seang-Mei and Montgomery, Grant W. and Campbell, Harry and Wilson, James F. and Vrijkotte, Tanja G. M. and Vrijheid, Martine and de Geus, Eco J. C. N. and Hayes, M. Geoffrey and Kadarmideen, Haja N. and Holm, Jens-Christian and Beilin, Lawrence J. and Pennell, Craig E. and Heinrich, Joachim and Adair, Linda S. and Borja, Judith B. and Mohlke, Karen L. and Eriksson, Johan G. and Widen, Elisabeth E. and Hattersley, Andrew T. and Spector, Tim D. and Kaehoenen, Mika and Viikari, Jorma S. and Lehtimaeki, Terho and Boomsma, Dorret I. and Sebert, Sylvain and Vollenweider, Peter and Sorensen, Thorkild I. A. and Bisgaard, Hans and Bonnelykke, Klaus and Murray, Jeffrey C. and Melbye, Mads and Nohr, Ellen A. and Mook-Kanamori, Dennis O. and Rivadeneira, Fernando and Hofman, Albert and Felix, Janine F. and Jaddoe, Vincent W. V. and Hansen, Torben and Pisinger, Charlotta and Vaag, Allan A. and Pedersen, Oluf and Uitterlinden, Andre G. and Jarvelin, Marjo-Riitta and Power, Christine and Hypponen, Elina and Scholtens, Denise M. and Lowe, William L. and Smith, George Davey and Timpson, Nicholas J. and Morris, Andrew P. and Wareham, Nicholas J. and Hakonarson, Hakon and Grant, Struan F. A. and Frayling, Timothy M. and Lawlor, Debbie A. and Njolstad, Pal R. and Johansson, Stefan and Ong, Ken K. and McCarthy, Mark I. and Perry, John R. B. and Evans, David M. and Freathy, Rachel M.}, title = {Maternal and fetal genetic effects on birth weight and their relevance to cardio-metabolic risk factors}, series = {Nature genetics}, volume = {51}, journal = {Nature genetics}, number = {5}, publisher = {Nature Publ. Group}, address = {New York}, organization = {EGG Consortium}, issn = {1061-4036}, pages = {804 -- +}, year = {2019}, abstract = {Birth weight variation is influenced by fetal and maternal genetic and non-genetic factors, and has been reproducibly associated with future cardio-metabolic health outcomes. In expanded genome-wide association analyses of own birth weight (n = 321,223) and offspring birth weight (n = 230,069 mothers), we identified 190 independent association signals (129 of which are novel). We used structural equation modeling to decompose the contributions of direct fetal and indirect maternal genetic effects, then applied Mendelian randomization to illuminate causal pathways. For example, both indirect maternal and direct fetal genetic effects drive the observational relationship between lower birth weight and higher later blood pressure: maternal blood pressure-raising alleles reduce offspring birth weight, but only direct fetal effects of these alleles, once inherited, increase later offspring blood pressure. Using maternal birth weight-lowering genotypes to proxy for an adverse intrauterine environment provided no evidence that it causally raises offspring blood pressure, indicating that the inverse birth weight-blood pressure association is attributable to genetic effects, and not to intrauterine programming.}, language = {en} } @article{BassoAltafimAltafimetal.2007, author = {Basso, Heitor Cury and Altafim, Ruy Alberto Pisani and Altafim, Ruy Alberto Pisani and Mellinger, Axel and Fang, Peng and Wirges, Werner and Gerhard, Reimund}, title = {Three-layer ferroelectrets from perforated Teflon-PTFE films fused between two homogeneous Teflon-FEP films}, isbn = {978-1-4244-1482-6}, year = {2007}, language = {en} } @article{FangWangWirgesetal.2011, author = {Fang, Peng and Wang, Feipeng and Wirges, Werner and Gerhard, Reimund and Basso, Heitor Cury}, title = {Three-layer piezoelectrets from fluorinated ethylene-propylene (FEP) copolymer films}, series = {Applied physics : A, Materials science \& processing}, volume = {103}, journal = {Applied physics : A, Materials science \& processing}, number = {2}, publisher = {Springer}, address = {New York}, issn = {0947-8396}, doi = {10.1007/s00339-010-6008-2}, pages = {455 -- 461}, year = {2011}, abstract = {A process for preparing three-layer piezoelectrets from fluorinated ethylene-propylene (FEP) copolymer films is introduced. Samples are made from commercial FEP films by means of laser cutting, laser bonding, electrode evaporation, and high-field poling. The observed dielectric-resonance spectra demonstrate the piezoelectricity of the FEP sandwiches. Piezoelectric d (33) coefficients up to a few hundred pC/N are achieved. Charging at elevated temperatures can increase the thermal stability of the piezoelectrets. Isothermal experiments for approximately 15 min demonstrate that samples charged at 140A degrees C keep their piezoelectric activity up to at least 120A degrees C and retain 70\% of their initial d (33) even at 130A degrees C. Acoustical measurements show a relatively flat frequency response in the range between 300 Hz and 20 kHz.}, language = {en} } @article{FangWegenerWirgesetal.2007, author = {Fang, Peng and Wegener, Michael and Wirges, Werner and Gerhard, Reimund and Zirkel, Larissa}, title = {Cellular polyethylene-naphthalate ferroelectrets : foaming in supercritical carbon dioxide, structural and electrical preparation, and resulting piezoelectricity}, issn = {0003-6951}, doi = {10.1063/1.2738365}, year = {2007}, abstract = {Polymer foams with electrically charged cellular voids, the so-called ferroelectrets, are soft piezoelectric transducer materials. Several polymers such as polyethylene terephthalate or cyclo-olefin copolymers are under investigation with respect to their suitability as ferroelectrets. Here, the authors report an additional ferroelectret polymer, cellular polyethylene-naphthalate (PEN), which was prepared from commercial uniform polymer films by means of foaming in supercritical carbon dioxide, inflation, biaxial stretching, electrical charging, and metallization. Piezoelectric d(33) coefficients of up to 140 pC/N demonstrate the suitability of such cellular PEN films for transducer applications. Their piezoelectricity is partially stable at elevated temperatures as high as 100 degrees C.}, language = {en} } @article{FangQiuWirgesetal.2010, author = {Fang, Peng and Qiu, Xunlin and Wirges, Werner and Gerhard, Reimund and Zirkel, Larissa}, title = {Polyethylene-naphthalate (PEN) ferroelectrets : cellular structure, piezoelectricity and thermal stability}, issn = {1070-9878}, doi = {10.1109/TDEI.2010.5539678}, year = {2010}, abstract = {Cellular polyethylene-naphthalate (PEN) ferroelectrets are useful as soft and flexible electromechanical transducer materials. Improved cellular PEN foams are prepared by means of a "voiding + inflation + stretching" process and investigated with respect to their structure and their applications-relevant properties. It is found that most of the cellular voids have heights below 8 mu m. The polymer walls do not allow sufficient gas exchange between the voids and the ambient atmosphere, when the cellular films are exposed to atmospheric pressures between a millibar and a few bars. As expected for ferroelectrets, a threshold voltage for charging is observed: A reasonable piezoelectric coefficient d(33) is only found when the charging voltage is higher than 4 kV. Furthermore, d(33) increases with charging voltage and reaches saturation at approximately 8 kV. Annealing after charging or charging at elevated temperatures may enhance the thermal stability of the PEN ferroelectrets. The d(33) of properly annealed samples is stable up to the respective annealing temperatures, but the annealing process reduces the piezoelectric activity of charged ferroelectret films to some extent. Samples charged at suitable elevated temperatures show much better thermal stability than those charged at room temperature, but the charging temperature should be limited to values below the material's glass-transition temperature T-g. Furthermore, the relevant elastic modulus c(33) of PEN ferroelectrets may decrease upon thermal treatment.}, language = {en} } @article{FangHollaenderWirgesetal.2012, author = {Fang, Peng and Hollaender, Lars and Wirges, Werner and Gerhard, Reimund}, title = {Piezoelectric d(33) coefficients in foamed and layered polymer piezoelectrets from dynamic mechano-electrical experiments, electro-mechanical resonance spectroscopy and acoustic-transducer measurements}, series = {Measurement science and technology}, volume = {23}, journal = {Measurement science and technology}, number = {3}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0957-0233}, doi = {10.1088/0957-0233/23/3/035604}, pages = {9}, year = {2012}, abstract = {Piezoelectrets are novel transducer materials which can be widely applied in sensors and actuators. Here, three techniques for determining piezoelectric d(33) coefficients of piezoelectrets are reviewed and compared. Two types of piezoelectrets, polyethylene-naphthalate (PEN) polymer-foam piezoelectrets and fluorinated ethylene-propylene (FEP) copolymer-layer piezoelectrets, have been prepared and measured by means of dynamic, resonance, and acoustical methods. The dynamic measurements show that the d(33) coefficient of PEN-foam samples clearly decreases with increasing stress, but 80\% of the initial d(33) can be retained after 1800 cycles of a continuous dynamic measurement in a mechanical fatigue test. The resonance measurements demonstrate that both PEN-foam and FEP-layer samples exhibit clear electro-mechanical resonances. PEN-foam samples show elastic moduli in the range from 1 to 12 MPa and d(33) values up to 500 pC N-1, while FEP-layer samples show homogeneous elastic moduli of about 0.3 MPa and d(33) values of about 280 pC N-1. The acoustical measurements reveal that both PEN-foam and FEP-layer samples exhibit stable frequency responses in the range from 5.7 to 20 kHz. In addition, d(33) coefficients obtained with different experimental methods are in good agreement with each other, which confirms the reliability of all three techniques.}, language = {en} } @article{FangMaLietal.2017, author = {Fang, Peng and Ma, Xingchen and Li, Xiangxin and Qiu, Xunlin and Gerhard, Reimund and Zhang, Xiaoqing and Li, Guanglin}, title = {Fabrication, Structure Characterization, and Performance Testing of Piezoelectret-Film Sensors for Recording Body Motion}, series = {IEEE Sensors Journal}, volume = {18}, journal = {IEEE Sensors Journal}, number = {1}, publisher = {Inst. of Electr. and Electronics Engineers}, address = {Piscataway}, issn = {1530-437X}, doi = {10.1109/JSEN.2017.2766663}, pages = {401 -- 412}, year = {2017}, abstract = {During muscle contractions, radial-force distributions are generated on muscle surfaces due to muscle-volume changes, from which the corresponding body motions can be recorded by means of so-called force myography (FMG). Piezo- or ferroelectrets are flexible piezoelectric materials with attractive materials and sensing properties. In addition to several other applications, they are suitable for detecting force variations by means of wearable devices. In this paper, we prepared piezoelectrets from cellular polypropylene films by optimizing the fabrication procedures, and developed an FMG-recording system based on piezoelectret sensors. Different hand and wrist movements were successfully detected on able-bodied subjects with the FMG system. The FMG patterns were evaluated and identified by means of linear discriminant analysis and artificial neural network algorithms, and average motion-classification accuracies of 96.1\% and 94.8\%, respectively, were obtained. This paper demonstrates the feasibility of using piezoelectret-film sensors for FMG and may thus lead to alternative methods for detecting body motion and to related applications, e.g., in biomedical engineering or structural-health monitoring.}, language = {en} } @phdthesis{Fang2010, author = {Fang, Peng}, title = {Preparation and investigation of polymer-foam films and polymer-layer systems for ferroelectrets}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-48412}, school = {Universit{\"a}t Potsdam}, year = {2010}, abstract = {Piezoelectric materials are very useful for applications in sensors and actuators. In addition to traditional ferroelectric ceramics and ferroelectric polymers, ferroelectrets have recently become a new group of piezoelectrics. Ferroelectrets are functional polymer systems for electromechanical transduction, with elastically heterogeneous cellular structures and internal quasi-permanent dipole moments. The piezoelectricity of ferroelectrets stems from linear changes of the dipole moments in response to external mechanical or electrical stress. Over the past two decades, polypropylene (PP) foams have been investigated with the aim of ferroelectret applications, and some products are already on the market. PP-foam ferroelectrets may exhibit piezoelectric d33 coefficients of 600 pC/N and more. Their operating temperature can, however, not be much higher than 60 °C. Recently developed polyethylene-terephthalate (PET) and cyclo-olefin copolymer (COC) foam ferroelectrets show slightly better d33 thermal stabilities, but usually at the price of smaller d33 values. Therefore, the main aim of this work is the development of new thermally stable ferroelectrets with appreciable piezoelectricity. Physical foaming is a promising technique for generating polymer foams from solid films without any pollution or impurity. Supercritical carbon dioxide (CO2) or nitrogen (N2) are usually employed as foaming agents due to their good solubility in several polymers. Polyethylene propylene (PEN) is a polyester with slightly better properties than PET. A "voiding + inflation + stretching" process has been specifically developed to prepare PEN foams. Solid PEN films are saturated with supercritical CO2 at high pressure and then thermally voided at high temperatures. Controlled inflation (Gas-Diffusion Expansion or GDE) is applied in order to adjust the void dimensions. Additional biaxial stretching decreases the void heights, since it is known lens-shaped voids lead to lower elastic moduli and therefore also to stronger piezoelectricity. Both, contact and corona charging are suitable for the electric charging of PEN foams. The light emission from the dielectric-barrier discharges (DBDs) can be clearly observed. Corona charging in a gas of high dielectric strength such as sulfur hexafluoride (SF6) results in higher gas-breakdown strength in the voids and therefore increases the piezoelectricity. PEN foams can exhibit piezoelectric d33 coefficients as high as 500 pC/N. Dielectric-resonance spectra show elastic moduli c33 of 1 - 12 MPa, anti-resonance frequencies of 0.2 - 0.8 MHz, and electromechanical coupling factors of 0.016 - 0.069. As expected, it is found that PEN foams show better thermal stability than PP and PET. Samples charged at room temperature can be utilized up to 80 - 100 °C. Annealing after charging or charging at elevated temperatures may improve thermal stabilities. Samples charged at suitable elevated temperatures show working temperatures as high as 110 - 120 °C. Acoustic measurements at frequencies of 2 Hz - 20 kHz show that PEN foams can be well applied in this frequency range. Fluorinated ethylene-propylene (FEP) copolymers are fluoropolymers with very good physical, chemical and electrical properties. The charge-storage ability of solid FEP films can be significantly improved by adding boron nitride (BN) filler particles. FEP foams are prepared by means of a one-step procedure consisting of CO2 saturation and subsequent in-situ high-temperature voiding. Piezoelectric d33 coefficients up to 40 pC/N are measured on such FEP foams. Mechanical fatigue tests show that the as-prepared PEN and FEP foams are mechanically stable for long periods of time. Although polymer-foam ferroelectrets have a high application potential, their piezoelectric properties strongly depend on the cellular morphology, i.e. on size, shape, and distribution of the voids. On the other hand, controlled preparation of optimized cellular structures is still a technical challenge. Consequently, new ferroelectrets based on polymer-layer system (sandwiches) have been prepared from FEP. By sandwiching an FEP mesh between two solid FEP films and fusing the polymer system with a laser beam, a well-designed uniform macroscopic cellular structure can be formed. Dielectric resonance spectroscopy reveals piezoelectric d33 coefficients as high as 350 pC/N, elastic moduli of about 0.3 MPa, anti-resonance frequencies of about 30 kHz, and electromechanical coupling factors of about 0.05. Samples charged at elevated temperatures show better thermal stabilities than those charged at room temperature, and the higher the charging temperature, the better is the stability. After proper charging at 140 °C, the working temperatures can be as high as 110 - 120 °C. Acoustic measurements at frequencies of 200 Hz - 20 kHz indicate that the FEP layer systems are suitable for applications at least in this range.}, language = {en} }