Yong Zhu

In this proposal, we aim to study and develop a transformative plant wearable sensor that can be deployed on-plant for continuous monitoring of biotic and abiotic stresses of plants and their microenvironment to inform plant health status and early detection of plant diseases. This multifunctional plant wearable sensor will include an array of ligand-functionalzied chemiresistive sensors to profile plant leaf VOCs and nanowire-based flexible sensors to monitor microclimate in parallel. The sensors will be prepared on a light-transparent, gas-permeable, and stretach substrate for long-term wearibility on live plants. In addition, a signal transmitter will be developed for wireless data acquistion and transmission. The system will be thourughly tested on tomato plants in the greenhouse for stress monitoring and disease detection.

The objective of this proposal is to realize a circular economic system for manufacturing of soft electronics where a coordinated set of sustainable manufacturing processes and a select group of novel biodegradable and reusable materials are seamlessly integrated. It is anticipated that all components of the device can be either biodegraded or recycled/reused, and the project will explore different end-of-life pathways from both technical, economic, and environmental perspectives (e.g., through life cycle assessment and techno-economic analysis). Our team has faculty members from mechanical engineering, chemistry, chemical engineering, Industrial Engineering, and sustainable engineering, allowing us to propose a hybrid approach from material design/synthesis all the way to device manufacturing.

Stroke is a leading cause of motor disability. A majority of stroke survivors exhibit upper and lower limb motor impairments, ranging from incapability of reaching and grasping objects to limited ambulation. The objective of this project is to develop a personalized, community-based rehabilitation system to improve daily functions of stroke survivors. The system will include three essential components ������������������ a nanomaterial-enabled multifunctional wearable sensor network to monitor arm and leg functional activities; a low-power data acquisition, processing, and transmission protocol; and a user interface (i.e., smart phone APP) to communicate training outcomes to the users and clinicians and receive feedback from the users and clinicians. The proposed community-based rehabilitation system will enable personalized, continuous rehabilitation during daily activities.

Emerging plant disease and pest outbreaks reduce food security, national security, human health, and the environment, with serious economic implications for North Carolina growers. These outbreaks may accelerate in coming decades due to shifts in the geographic distributions of pests, pathogens and vectors in response to climate change and commerce. Data-driven agbioscience tools can help growers solve pest and disease problems in the field more quickly but there is an urgent need to harness game-changing technologies. Computing devices are now embedded in our personal lives with sensors, wireless technology, and connectivity in the ����������������Internet of Things��������������� (IoT) but these technologies have yet to be scaled to agriculture. Our interdisciplinary team will build transformative sensor technology to identify plant pathogens, link local pathogen data and weather data, bioinformatics tools (pathogen genotypes), and use data driven analytics to map outbreaks, estimate pest and pathogen risk and economic damage, in order to coordinate response to emerging diseases, and contain threats. Sensor-supported early and accurate detection of pathogens before an outbreak becomes wide-spread in growing crops will significantly reduce pesticide use and increase crop yields.

The currently wearable sensors for sports applications on the market can only capture body motion or limb motion, but not specific joint angles, at least not directly. On the other hand, it is challenging to directly measure joint angles using a wearable sensor because the sensor must be highly stretchable, resilient and reliable under many cycles of joint bending, while also being unobtrusive and easy to wear. In this proposal, we aim to develop a wearable system that can directly track joint angles using our stretchable strain sensors.

Nanomaterials such as metal nanowires play a fundamental role in enabling the unique properties of nanomechanical, and nano-electro-mechanical systems and devices. Most experimental and computational studies of the mechanical properties, plasticity and failure of metal nanowires have focused on intrinsic and extrinsic size effects, which cover changes in mechanical properties over multiple length scales. In contrast, due to shortcomings in both computational and experimental capabilities, the reliability of nanowires, which depend on deformation and plasticity over multiple time scales, and which is essential to predicting device performance over its lifespan, has not been widely investigated. Therefore, the goal of this proposal is to develop a fundamental understanding of how strain rate impacts the rate-dependent plasticity transitions, and thus the mechanical behavior and properties of metal nanowires.

A novel thermo-mechanical fatigue (TMF) testing system, referred by miniature TMF (MTMF) system has been developed at NCSU for in-situ testing of miniature specimens within Scanning Electron Microscopes (SEM). The MTMF is capable of prescribing axial-torsional loading to solid specimen and axial-torsional-internal pressure loading to tubular specimen of 1 mm diameter at elevated temperatures (up to 1000oC) to investigate deformation of microstructure and failure mechanism in real time. Currently, in-situ SEM testing with the MTMF is performed at the Analytical Instrumentation Facility (AIF) at NCSU. This poses a serious restriction to investigate failure mechanisms of very high temperature reactor (VHTRs) materials primarily because with a user facility, such as AIF, we can only perform short-term tests that span over few days. However, fatigue, creep and creep-fatigue tests for VHTR materials may span from few days to several weeks. Hence, existing SEMs on campus are not available for long-term in-situ testing of VHTR materials. Currently, fatigue, creep and creep-fatigue failure mechanisms of new and existing alloys are mostly investigated through ex-situ testing or short duration in-situ uniaxial testing within SEM. Consequently, initiation and propagation of many failure mechanisms, especially interactions between creep and fatigue mechanisms in reducing high temperature component lives remain unknown. Hence, developing a shared in-situ testing laboratory (ISTL) is essential to allow NCSU researchers to perform novel research on nuclear materials addressing issues of fatigue, creep and creep-fatigue failure mechanisms. The proposed ISTL dedicated to performing long-term fatigue, creep and creep-fatigue tests is in critical need to develop design criteria of VHTR materials for ASME Code Sec III Div 5. However, existing facilities at NCSU or any other universities or national labs in the nation do not have a facility dedicated to perform long term tests representing realistic loading conditions of VHTR. Therefore, a suitable SEM compatible with the MTMF system at NCSU is proposed to be acquired to develop an ISTL to address high temperature nuclear materials and ASME Code issues. With the availability of such a ISTL, uniaxial and multiaxial cyclic experiments prescribing realistic thermo-mechanical fatigue (TMF), creep and creep-fatigue loading can be performed on specimens of VHTR materials, such as Alloy 617, 316H, 800H, Grade 91 steel, for addressing the high temperature component design and development issues. Finally, because of the size of commercially available TMF systems, these cannot be used for in-situ SEM testing, which is essential for investigating existing alloys and developing new alloy for VHTRs. Hence, acquisition of a SEM will give the NCSU research community unprecedented capability to perform fundamental research and educate next generation scientists in studying real-time long-term microstructure evolution of nuclear materials under uniaxial and multiaxial loading. In addition, the proposed equipment will allow training undergraduate and graduate students and postdocs in performing material characterization using advanced techniques and provide hands on experiences to students in various undergraduate and graduate courses.

The objective of this proposal is to develop and utilize novel in situ TEM nano-thermo-mechanical testing and atomistic modeling for elucidating the temperature, strain rate and sample size effects on the strength and brittle-to-ductile transition (BDT) in Si nanowires. While Si nanowires at room temperature have been measured with brittle fracture, our preliminary in situ testing inside transmission electron microscope (TEM) have shown that an increase of temperature can result in a fascinating BDT behavior in Si nanowires by activating the dislocation-mediated plastic deformation.

In the United States, about 16,000 service members and veterans each year suffer a cerebral stroke. Since 9/11, 18,000-25,000 service members each year suffer a traumatic brain injury (TBI), and 11% of them are moderate or severe TBI. Following a brain injury, approximately 66% of them show impaired hand functions, and the recovery of hand function is most challenging among different functions, despite extensive therapy. As a result, independent living and return to service duty or to the work force is severely limited. Different hand orthoses are commercially available, which can improve the efficacy of rehabilitation, facilitate active involvement of patients, and assist users completing daily tasks. However, we currently lack a continuous monitoring of hand usage during daily activities when orthotic hand users return to their home environment. A lack of such critical information in the real-world could prevent clinicians from making decisions regarding the type of the orthosis prescription and the timing of subsequent adjustment, therefore reducing the efficacy of orthoses functions. Accordingly, our objective is to establish integrated real-time outcome measures for orthotic hand users based on continuous monitoring of hand utility in daily life. In a four-year period, we will first validate our continuous measurement of hand functions using existing standardized clinical outcome assessments (2.5 years). Concurrently, we will optimize our wearable sensor sleeve system that can be used for continuous tracking of daily use of the hand. In the remaining 1.5 years, we will establish an assessment toolkit integrating continuous hand tracking with standard clinical assessments and user feedback. The integrated outcomes will capture different aspects of hand performance, and the most severe aspect of motor deficit that should be targeted. The clinical applicability of our proposed work is high. The optimized sensing system, with highly stretchable sensors and textile sleeve, low profile electronics, and cloud computing, will have minimal interference to users using daily activities, and thus presents a low barrier for clinical adoption. The integrated outcome measures will capture critical aspects of hand performance including mechanisms of impairments. These outcome measures will be highly informative and intuitive to both patients and clinicians.

The overarching goal of this project is to fabricate large-area, high-resolution, stretchable pressure sensor arrays for e-skin at low cost by integrating organic semiconductors, AgNW conductors, and elastomers. The devices will be fabricated using several scalable nanomanufacturing techniques including gravure printing, transfer printing, and electrohydrodynamic (EHD) printing.