@article{li_ju_zhou_knowles_rosenberg_flewwellin_kose_jur_2021, title={Airbrushed PVDF-TrFE Fibrous Sensors for E-Textiles}, volume={3}, ISSN={["2637-6113"]}, url={https://doi.org/10.1021/acsaelm.1c00802}, DOI={10.1021/acsaelm.1c00802}, abstractNote={The low-temperature processing, inherent flexibility, and biocompatibility of piezoelectric polymers such as poly(vinylidene fluoride) (PVDF)-based materials enable the creation of soft wearable sensors, energy harvesters, and actuators. Of the various processing techniques, electrospinning is the most widely adopted process to form PVDF nanofiber scaffolds with enhanced piezoelectric properties such that they do not require further post-processing such as mechanical drawing, electrical poling, or thermal annealing. However, electrospinning requires long periods of time to form sufficiently thick PVDF nanofiber scaffolds and requires extremely high voltages to form scaffolds with enhanced piezoelectric properties, which limits the number of usable substrates, thus restricting the integration and use of electrospun PVDF scaffolds into wearable textile platforms. In this work, we propose a facile processing technique to airbrush PVDF–trifluoroethylene (TrFE) nanofiber scaffolds directly onto textile substrates. We tune the polymer concentration (4, 6, and 8 wt %) and the spray distance (5, 12.5, and 20 cm) to understand their effects on the morphology and crystal structure of the fibrous scaffolds. The characterization results show that increasing the polymer wt % encourages the formation of fibrous morphologies and a β-phase crystal structure. We then demonstrate how the airbrushed PVDF–TrFE scaffolds can be easily integrated onto conductive inkjet-printed nonwoven textile substrates to form airbrushed piezoelectric textile devices (APTDs). The APTDs exhibit maximum open-circuit voltages of 667.1 ± 162.1 mV under tapping and 276.9 ± 59.0 mV under bending deformations. The APTDs also show an areal power density of 0.04 μW/cm2, which is 40× times higher compared to previously reported airbrushed PVDF scaffolds. Lastly, we sew APTDs into wearable textile platforms to create fully textile-integrated devices with applications in sensing a basketball shooting form.}, number={12}, journal={ACS APPLIED ELECTRONIC MATERIALS}, publisher={American Chemical Society (ACS)}, author={Li, Braden M. and Ju, Beomjun and Zhou, Ying and Knowles, Caitlin G. and Rosenberg, Zoe and Flewwellin, Tashana J. and Kose, Furkan and Jur, Jesse S.}, year={2021}, month={Dec}, pages={5307–5326} }
 @article{li_mills_flewwellin_herzberg_bosari_lim_jia_jur_2021, title={Influence of Armband Form Factors on Wearable ECG Monitoring Performance}, volume={21}, ISSN={["1558-1748"]}, DOI={10.1109/JSEN.2021.3059997}, abstractNote={In the current state of innovation in wearable technology, there is a vast array of biomonitoring devices available to record electrocardiogram (ECG) in users, a key indicator of cardiovascular health. Of these devices, armband form factors serve as a convenient all-in-one platform for integration of electronic systems; yet, much of the current literature does not address the appropriate electrode location nor contact pressures necessary to achieve reliable system level ECG sensing. Therefore, this paper will elucidate the role of electrode location and contact pressure on the ECG sensing performance of an electronic textile (E-textile) armband worn on the upper left arm. We first carry out an ECG signal characterization to validate the ideal armband electrode placement necessary to measure high quality signals without sacrificing practical assembly of the armband. We then model and experimentally quantify the contact pressure between the armband onto the upper arm as a function of armband size, a critical parameter dictating skin-electrode impedance and ECG signal quality. Finally, we evaluate how the size of the armband form factor affects its ECG sensing performance. Our experimental results confirm that armbands exhibiting modeled contact pressures between 500 Pa to 1500 Pa can acquire ECG signals. However, armband sizes exhibiting experimental contact pressures of 1297 ± 102 Pa demonstrate the best performance with similar signal-to-noise ratios (SNR) compared to wet electrode benchmarks. The fundamental design parameters discussed in this work serve as a benchmark for the design of future E-textile and wearable form factors with efficient sensing performance.}, number={9}, journal={IEEE SENSORS JOURNAL}, author={Li, Braden M. and Mills, Amanda C. and Flewwellin, Tashana J. and Herzberg, Jacklyn L. and Bosari, Azin Saberi and Lim, Michael and Jia, Yaoyao and Jur, Jesse S.}, year={2021}, month={May}, pages={11046–11060} }
 @article{li_yildiz_mills_flewwellin_bradford_jur_2020, title={Iron-on carbon nanotube (CNT) thin films for biosensing E-Textile applications}, volume={168}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2020.06.057}, abstractNote={Conductive carbon nanotube-thermoplastic polyurethane (CNT-TPU) composite thin films are patterned and integrated onto knitted textile substrates to form electronic textile (E-Textile) dry electrodes. Vertically aligned CNT arrays are mechanically drawn into thin CNT sheets and infiltrated with a TPU solution to form the CNT-TPU thin films. The CNT-TPU thin films are then heat laminated onto knitted textile substrates to form dry E-Textile electrodes. To understand the wearability of our CNT-TPU thin films we perform an in-depth analysis of the films’ electromechanical properties, electrical impedance, and electrocardiogram (ECG) sensing performance. The electromechanical coupling between the CNT thin films and knitted textile substrates show a strong anisotropic dependence between the CNT film alignment and textile knit structure. Further analysis into the CNT thin films reveal that larger electrode sizes with a larger number of CNT sheet layers in the film, lead to more favorable impedance behaviors and ECG sensing capabilities. As a wearable demonstration, we fabricate a textile arm sleeve integrated with CNT thin film electrodes to form an ECG sensing E-Textile system. The proposed E-Textile sleeve demonstrates the practicality of our CNT thin films and show promise for other E-Textile and wearable applications.}, journal={CARBON}, author={Li, Braden M. and Yildiz, Ozkan and Mills, Amanda C. and Flewwellin, Tashana J. and Bradford, Philip D. and Jur, Jesse S.}, year={2020}, month={Oct}, pages={673–683} }