Person: Le Floch, Paul
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Le Floch
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Paul
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Le Floch, Paul
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Publication Stretchable Electrets: Nanoparticle–Elastomer Composites(American Chemical Society (ACS), 2020-05-15) Zhang, Shuwen; Wang, Yecheng; Yao, Xi; Le Floch, Paul; Yang, Xuxu; Liu, Jia; Suo, ZhigangPublication Stretchable Seal(American Chemical Society (ACS), 2018-07-17) Le Floch, Paul; Meixuanzi, Shi; Tang, Jingda; Liu, Junjie; Suo, ZhigangMany stretchable electronic devices require stretchable hermetic seals. However, stretchability and permeability are inextricably linked at the molecular level: stretchable, low-permeability materials do not exit. We collect data for permeation of water and oxygen in many materials and describe the scaling relations for both flat and wrinkled seals. Whereas flat seals struggle to fulfill the simultaneous requirements of stretchability, low stiffness and low transmissibility, wrinkled seals can fulfill them readily. We further explore the behavior of wrinkled seals under cyclic stretch using aluminum, polyethylene and silica films on elastomer substrates. The wrinkled aluminum develops fatigue cracks after a small number of cycles, but the wrinkled polyethylene and silica maintain low transmissibility after 10,000 cycles of tensile strain.Publication Wearable and washable conductors for active textiles(American Chemical Society (ACS), 2017) Le Floch, Paul; Yao, Xi; Liu, Qihan; Wang, Zhengjin; Nian, Guodong; Sun, Yu; Jia, Li; Suo, ZhigangThe emergence of stretchable electronics and its potential integration with textiles have highlighted a challenge: textiles are wearable and washable, but electronic devices are not. Many stretchable conductors have been developed to enable wearable active textiles, but little has been done to make them washable. Here we demonstrate a new class of stretchable conductors that can endure wearing and washing conditions commonly associated with textiles. Such a conductor consists of a hydrogel, a dissolved hygroscopic salt, and a butyl rubber coating. The hygroscopic salt enables ionic conduction, and matches the relative humidity of the hydrogel to the average ambient relative humidity. The butyl rubber coating prevents the loss and gain of water due to the daily fluctuation of ambient relative humidity. We develop the chemistry of dip coating the butyl rubber onto the hydrogel, using silanes to achieve both the crosslink of the butyl rubber and the adhesion between the butyl rubber and the hydrogel. We test the endurance of the conductor by soaking it in detergent while stretching it cyclically, and by machine-washing it. The loss of water and salt is minimal. It is hoped that these conductors open applications in healthcare, entertainment, and fashion.Publication Fundamental Limits to the Electrochemical Impedance Stability of Dielectric Elastomers in Bioelectronics(American Chemical Society (ACS), 2019-11-28) Le Floch, Paul; Molinari, Nicola; Nan, Kewang; Zhang, Shuwen; Kozinsky, Boris; Suo, Zhigang; Liu, JiaIncorporation of elastomers into bioelectronics that reduces the mechanical mismatch between electronics and biological systems could potentially improve the long-term electronics–tissue interface. However, the chronic stability of elastomers in physiological conditions has not been systematically studied. Here, using electrochemical impedance spectrum we find that the electrochemical impedance of dielectric elastomers degrades over time in physiological environments. Both experimental and computational results reveal that this phenomenon is due to the diffusion of ions from the physiological solution into elastomers over time. Their conductivity increases by 6 orders of magnitude up to 10–8 S/m. When the passivated conductors are also composed of intrinsically stretchable materials, higher leakage currents can be detected. Scaling analyses suggest fundamental limitations to the electrical performances of interconnects made of stretchable materials.Publication Cyborg Organoids: Implantation of Nanoelectronics via Organogenesis for Tissue-Wide Electrophysiology(American Chemical Society (ACS), 2019-07-26) Li, Qiang; Nan, Kewang; Le Floch, Paul; Lin, Zuwan; Sheng, Hao; Blum, Thomas S.; Liu, Jia; Blum, ThomasTissue-wide electrophysiology with single-cell and millisecond spatiotemporal resolution is critical for heart and brain studies. Issues arise, however, from the invasive, localized implantation of electronics that destroys well-connected cellular networks within matured organs. Here, we report the creation of cyborg organoids: the three-dimensional (3D) assembly of soft, stretchable mesh nanoelectronics across the entire organoid by the cell–cell attraction forces from 2D-to-3D tissue reconfiguration during organogenesis. We demonstrate that stretchable mesh nanoelectronics can migrate with and grow into the initial 2D cell layers to form the 3D organoid structure with minimal impact on tissue growth and differentiation. The intimate contact between the dispersed nanoelectronics and cells enables us to chronically and systematically observe the evolution, propagation, and synchronization of the bursting dynamics in human cardiac organoids through their entire organogenesis.