Purim Ladpli

Pneumatic stimulation of C. elegans mechanoreceptor neurons in a microfluidic trap

New tools for applying force to animals, tissues, and cells are critically needed in order to advance the field of mechanobiology, as few existing tools enable simultaneous imaging of tissue and cell deformation as well as cellular activity in live animals. Here, we introduce a novel microfluidic device that enables high-resolution optical imaging of cellular deformations and activity while applying precise mechanical stimuli to the surface of the worms cuticle with a pneumatic pressure reservoir. To evaluate device performance, we compared analytical and numerical simulations conducted during the design process to empirical measurements made with fabricated devices. Leveraging the well-characterized touch receptor neurons (TRNs) with an optogenetic calcium indicator as a model mechanoreceptor neuron, we established that individual neurons can be stimulated and that the device can effectively deliver steps as well as more complex stimulus patterns. This microfluidic device is therefore a valuable platform for investigating the mechanobiology of living animals and their mechanosensitive neurons.

Battery charge and health state monitoring via ultrasonic guided-wave-based methods using built-in piezoelectric transducers

This work presents a novel scalable and field-deployable framework for monitoring lithium-ion (Li-ion) battery state of charge (SoC) and state of health (SoH), based on ultrasonic guided waves using low-profile built-in piezoelectric transducers. The feasibility of this technique is demonstrated through experiments using surface-mounted piezoelectric disc transducers on commercial Li-ion pouch batteries. Pitch-catch guided-wave propagation is performed in synchronization with electrical charge and discharge cycling, and cycle life testing. Simple time-domain analysis shows strong and repeatable correlation between waveform signal parameters, and battery SoC and SoH. The correlation thus provides a building block for constructing a technique for accurate real-time monitoring of battery charge and health states using ultrasonic guided-wave signals. Moreover, capacity-differential signal analysis reveals the underlying physical changes associated with cyclic electrochemical activities and phase transitioning. This finding allows accurate pinpointing of the root cause of capacity fade and mechanical degradation. The results of this study indicate that the use of guided waves can potentially offer a new avenue for in-situ characterization of Li-ion batteries, providing insight on the complex coupling between electrochemistry and mechanics, heretofore not fully understood within the scientific community.

Characterization of Distributed Microfabricated Strain Gauges on Stretchable Sensor Networks for Structural Applications

Smart structures mimic biological systems by using thousands of sensors serving as a nervous system analog. One approach to give structures this sensing ability is to develop a multifunctional sensor network. Previous work has demonstrated stretchable sensor networks consisting of temperature sensors and impact detectors for monitoring external environments and interacting with other objects. The objective of this work is to develop distributed, robust and reliable strain gauges for obtaining the strain distribution of a designated region on the target structure. Here, we report a stretchable network that has 27 rosette strain gauges, 6 resistive temperature devices and 8 piezoelectric transducers symmetrically distributed over an area of 150 × 150 mm to map and quantify multiple physical stimuli with a spatial resolution of 2.5 × 2.5 mm. We performed computational modeling of the network stretching process to improve measurement accuracy and conducted experimental characterizations of the microfabricated strain gauges to verify their gauge factor and temperature coefficient. Collectively, the results represent a robust and reliable sensing system that is able to generate a distributed strain profile of a common structure. The reported strain gauge network may find a wide range of applications in morphing wings, smart buildings, autonomous cars and intelligent robots.

Numerical Model for Characterization of Multifunctional Energy Storage Composite Cells, Modules, and Systems

Recent work on multifunctional materials has demonstrated that high-strength composites could be integrated with active Li-ion battery material to create high strength and high energy density storage structures that could meet the transportation requirements on mobility and energy storage density. However, the performance and the design of the multifunctional materials require fundamental understanding of the mechanical behavior of the integrated Multifunctional Energy Storage (MES) Composites systems under various loading conditions. Characterization of this new class of multifunctional materials would become very challenging without an adequate simulation model to guide the tests and validate the results. Therefore, this work presents the mechanical simulation and design of the MES Composites system that consists of multiple thin battery layers, polymer reinforcements, and carbon fiber composites, which results significant challenges in simulation and modeling. To tackle these issues, homogenization techniques were adopted to characterize the multi-layer properties of battery material with physics-based constitutive equations combined with non-linear deformation theories to handle the interface between the battery layers. Second, both mechanical and electrical damage and failure modes among battery materials, polymer reinforcements and carbon fiberpolymer interfaces were characterized through appropriate models and experiments. The model of MES Composite has been implemented in a commercial finite element code. A comparison of structural response and failure modes from numerical simulations and experimental tests will be presented in the paper. The simulated strain distribution and its application to Structural Health Monitoring (SHM) on MES Composites will also be discussed. The results of the study showed that the predictions of elastic and damage responses of MES Composites at various loading condition agreed with the test data. With appropriate material parameters determined from experiments, this multi-physics model can be used as a necessary tool to characterize a failure envelop that governs the design of MES Composites under specified electrical and mechanical loads.

Decision Making for Reference-Free Damage Detection

This paper concerns a reflection on a new decision boundary technique devoted for baseline-free damage detection purpose. Its scope focuses in studying analytically the impact of an unknown disturbance on the behavior of a monitored structure, through linear and nonlinear perturbation models. These perturbation models are introduced to interpret how an unknown disturbance away linearly and nonlinearly a monitored structure from its initial state, which is a healthy one, to its current state, which can be damaged or a healthy one that has undergone environmental/operational variations. To quantify the amount of that unknown disturbance effect, matrix perturbation theory is addressed to define two analytical bounds. The gap between them gives the decision regarding the monitored structure current state. The effectiveness of the proposed approach is demonstrated through an experimental setup of a test coupon aluminum plate, which has undergone varying loads and temperatures conditions, and crack damage cases. doi: 10.12783/SHM2015/367

Multifunctional Energy Storage Composites for SHM Distributed Sensor Networks

SHM-based structures with embedded sensors and hardware have posed a great demand in distributed, in-situ power sources. This paper introduces the novel Multifunctional-Energy-Storage Composites (MES Composites) which highlights a unique integration technique for embedding lithium-ion battery materials in structural carbon-fiber-reinforced-polymers (CFRP). Unlike standard lithium-ion pouch cells, the MES Composites maximizes material utilization by using CFRP facesheets to house the electrochemistry. Through-thickness polymer reinforcements are implemented to allow load transfer between the two facesheets, analogous to the sandwich structure construction. A feasibility study and preliminary characterization have been completed and have shown that the same electrochemical performance as a standard Li-ion cell could be maintained, while achieving high bending rigidity. doi: 10.12783/SHM2015/276