More Like this

1. Ionic polymer metal composite compression sensors with 3D-structured interfaces

   https://doi.org/https://doi.org/10.1088/1361-665X/ac3431  

   Rebecca Histed, Justin Ngo ( November 2021 , Smart materials and structures)

   In this paper, we report the development of tailored 3D-structured (engineered) polymer-metal interfaces to create enhanced ‘engineered ionic polymer metal composite’ (eIPMC) sensors towards soft, self-powered, high sensitivity strain sensor applications. We introduce a novel advanced additive manufacturing approach to tailor the morphology of the polymer-electrode interfaces via inkjet-printed polymer microscale features. We hypothesize that these features can promote inhomogeneous strain within the material upon the application of external pressure, responsible for improved compression sensing performance. We formalize a minimal physics-based chemoelectromechanical model to predict the linear sensor behavior of eIPMCs in both open-circuit and short-circuit sensing conditions. The model accounts for polymer-electrode interfacial topography to define the inhomogeneous mechanical response driving electrochemical transport in the eIPMC. Electrochemical experiments demonstrate improved electrochemical properties of the inkjet-printed eIPMCs as compared to the standard IPMC sensors fabricated from Nafion polymer sheets. Similarly, compression sensing results show a significant increase in sensing performance of inkjet-printed eIPMC. We also introduce two alternative methods of eIPMC fabrication for sub-millimeter features, namely filament-based fused-deposition manufacturing and stencil printing, and experimentally demonstrate their improved sensing performance. Our results demonstrate increasing voltage output associated to increasing applied mechanical pressure and enhanced performance of the proposed eIPMC sensors against traditional IPMC based compression sensors. 

   more » « less
2. Ionic Polymer Metal Composite Sensors With Engineered Interfaces (eIPMCs): Compression Sensing Modeling and Experiments

   https://doi.org/10.1115/DSCC2020-3289  

   Histed, Rebecca ; Ngo, Justin ; Hussain, Omar A. ; Lapins, Chantel ; Leang, Kam K. ; Liao, Yiliang ; Aureli, Matteo ( October 2020 , ASME 2020 Dynamic Systems and Control Conference)

   null (Ed.)

   In this paper, we examine the development of tailored 3D-structured (engineered) polymer-metal interfaces to create enhanced ionic polymer-metal composite (eIPMC) sensors towards soft, self-powered, high sensitivity strain sensor applications. First, a physics-based chemoelectromechanical model is developed to predict the sensor behavior of eIPMCs by incorporating structure microfeature effects in the mechanical response of the material. The model incorporates electrode surface properties, such as microscale feature thickness, size and spacing, to help define the mechanical response and transport characteristics of the polymer-electrode interface. Second, two novel approaches are described to create functional samples of eIPMC sensors using fused deposition manufacturing and inkjet printing technologies. Sample eIPMC sensors are fabricated for experimental characterization. Finally, experimental results are provided to show superior performance in the sensing capabilities compared to traditional sensors fabricated from sheet-form material. The results also validate important predictive aspects of the proposed minimal model.

    

   more » « less
3. Deep-learning-assisted printed liquid metal sensory system for wearable applications and boxing training

   https://doi.org/10.1038/s41528-023-00272-1  

   Qiu, Ye ; Zou, Zhihui ; Zou, Zhanan ; Setiawan, Nikolas Kurnia ; Dikshit, Karan Vivek ; Whiting, Gregory ; Yang, Fan ; Zhang, Wenan ; Lu, Jiutian ; Zhong, Bingqing ; et al ( August 2023 , npj Flexible Electronics)

   Liquid metal (LM) exhibits a distinct combination of high electrical conductivity comparable to that of metals and exceptional deformability derived from its liquid state, thus it is considered a promising material for high-performance soft electronics. However, rapid patterning LM to achieve a sensory system with high sensitivity remains a challenge, mainly attributed to the poor rheological property and wettability. Here, we report a rheological modification strategy of LM and strain redistribution mechanics to simultaneously simplify the scalable manufacturing process and significantly enhance the sensitivity of LM sensors. By incorporating SiO₂particles into LM, the modulus, yield stress, and viscosity of the LM-SiO₂composite are drastically enhanced, enabling 3D printability on soft materials for stretchable electronics. The sensors based on printed LM-SiO₂composite show excellent mechanical flexibility, robustness, strain, and pressure sensing performances. Such sensors are integrated onto different locations of the human body for wearable applications. Furthermore, by integrating onto a tactile glove, the synergistic effect of strain and pressure sensing can decode the clenching posture and hitting strength in boxing training. When assisted by a deep-learning algorithm, this tactile glove can achieve recognition of the technical execution of boxing punches, such as jab, swing, uppercut, and combination punches, with 90.5% accuracy. This integrated multifunctional sensory system can find wide applications in smart sport-training, intelligent soft robotics, and human-machine interfaces.

    

   more » « less
4. Surface roughness effects on ionic polymer-metal composite (IPMC) sensitivity for compression loads

   https://doi.org/10.1117/12.2613127  

   Nagel, William S. ; Hussain, Omar A. ; Fakharian, Omid ; Aureli, Matteo ; Leang, Kam K. ( January 2022 , Electroactive Polymer Actuators and Devices (EAPAD) XXIV)

   The soft and compliant nature of ionic polymer-metal composite (IPMC) sensors has recently been investigated for various applications in soft robotic and mechatronic devices. Recent results of physics-based chemoelectromechanical modeling suggest that IPMC asymmetric surface roughening may enhance the sensitivity under compression. This paper presents initial experimental results on IPMC compression sensors fabricated with varying degrees of asymmetric surface roughness. The roughness is created through a simple mechanical sanding process on the base polymer material, referred to as "polymer abrading technique'", followed by traditional electroless plating to create electrodes. Sample sensors are characterized by measuring the voltage response under different compressive loads. The results show consistently increased sensor sensitivity of the asymmetrically roughened IPMCs versus a control sample. Sensitivity increases non-monotonically with rougher electrode surfaces, where maximum sensitivity of about 0.0433 mV/kPa is achieved with sensor electrodes with 53-74~micrometer abrasions. More variability is also observed through augmented electrode roughness, suggesting greater flexibility for IPMC sensor design. These results align with predictions from the existing physics-based chemoelectromechanical model. 

   more » « less
5. Fully inkjet-printed multilayered graphene-based flexible electrodes for repeatable electrochemical response

   https://doi.org/10.1039/d0ra04786d  

   Pandhi, Twinkle ; Cornwell, Casey ; Fujimoto, Kiyo ; Barnes, Pete ; Cox, Jasmine ; Xiong, Hui ; Davis, Paul H. ; Subbaraman, Harish ; Koehne, Jessica E. ; Estrada, David ( October 2020 , RSC Advances)

   null (Ed.)

   Graphene has proven to be useful in biosensing applications. However, one of the main hurdles with printed graphene-based electrodes is achieving repeatable electrochemical performance from one printed electrode to another. We have developed a consistent fabrication process to control the sheet resistance of inkjet-printed graphene electrodes, thereby accomplishing repeatable electrochemical performance. Herein, we investigated the electrochemical properties of multilayered graphene (MLG) electrodes fully inkjet-printed (IJP) on flexible Kapton substrates. The electrodes were fabricated by inkjet printing three materials – (1) a conductive silver ink for electrical contact, (2) an insulating dielectric ink, and (3) MLG ink as the sensing material. The selected materials and fabrication methods provided great control over the ink rheology and material deposition, which enabled stable and repeatable electrochemical response: bending tests revealed the electrochemical behavior of these sensors remained consistent over 1000 bend cycles. Due to the abundance of structural defects ( e.g. , edge defects) present in the exfoliated graphene platelets, cyclic voltammetry (CV) of the graphene electrodes showed good electron transfer ( k = 1.125 × 10 −2 cm s −1 ) with a detection limit (0.01 mM) for the ferric/ferrocyanide redox couple, [Fe(CN) 6 ] −3/−4 , which is comparable or superior to modified graphene or graphene oxide-based sensors. Additionally, the potentiometric response of the electrodes displayed good sensitivity over the pH range of 4–10. Moreover, a fully IJP three-electrode device (MLG, platinum, and Ag/AgCl) also showed quasi-reversibility compared to a single IJP MLG electrode device. These findings demonstrate significant promise for scalable fabrication of a flexible, low cost, and fully-IJP wearable sensor system needed for space, military, and commercial biosensing applications. 

   more » « less