@article{nozariasbmarz_suarez_dycus_cabral_lebeau_ozturk_vashaee_2020, title={Thermoelectric generators for wearable body heat harvesting: Material and device concurrent optimization}, volume={67}, ISSN={["2211-3282"]}, DOI={10.1016/j.nanoen.2019.104265}, abstractNote={Body heat harvesting systems based on thermoelectric generators (TEGs) can play a significant role in wearable electronics intended for continuous, long-term health monitoring. However, to date, the harvested power density from the body using TEGs is limited to a few micro-watts per square centimeter, which is not sufficient to turn on many wearables. The thermoelectric materials research has been mainly focused on enhancing the single parameter zT, which is insufficient to meet the requirements for wearable applications. To develop TEGs that work effectively in wearable devices, one has to consider the material, device, and system requirements concurrently. Due to the lack of an efficient heatsink and the skin thermal resistance, a key challenge to achieving this goal is to design systems that maximize the temperature differential across the TEG while not compromising the body comfort. This requires favoring approaches that deliver the largest possible device thermal resistance relative to the external parasitic resistances. Therefore, materials with low thermal conductivity are critically important to maximize the temperature gradient. Also, to achieve a high boost converter efficiency, wearable TEGs need to have the highest possible output voltage, which calls for a high Seebeck coefficient. At the device level, dimensions of the legs (length versus the base area) and fill factor are both critical parameters to ensure that the parasitic thermal resistances are again negligible compared to the resistance of the module itself. In this study, the concurrent impact of material and device parameters on the efficiency of wearable TEGs is considered. Nanocomposite thermoelectric materials based on bismuth telluride alloys were synthesized using microwave processing and optimized to meet the requirements of wearable TEGs. Microwave energy decrystallized the material leading to a strong reduction of the thermal conductivity while maintaining a high zT at the body temperature. A comprehensive quasi-3D analytical model was developed and used to optimize the material and device parameters. The nanocomposite TEG produced 44 μW/cm2 under no air flow condition, and 156.5 μW/cm2 under airflow. In comparison to commercial TEGs tested under similar conditions, the nanocomposite based TEGs exhibited 4–7 times higher power density on the human body depending on the convective cooling conditions.}, journal={NANO ENERGY}, author={Nozariasbmarz, Amin and Suarez, Francisco and Dycus, J. Houston and Cabral, Matthew J. and LeBeau, James M. and Ozturk, Mehmet C. and Vashaee, Daryoosh}, year={2020}, month={Jan} }
 @misc{nozariasbmarz_agarwal_coutant_hall_liu_liu_malhotra_norouzzadeh_oeztuerk_ramesh_et al._2017, title={Thermoelectric silicides: A review}, volume={56}, ISSN={["1347-4065"]}, url={http://dx.doi.org/10.7567/jjap.56.05da04}, DOI={10.7567/jjap.56.05da04}, abstractNote={Traditional research on thermoelectric materials focused on improving the figure-of-merit zT to enhance the energy conversion efficiency. With further growth and commercialization of thermoelectric technology beyond niche applications, other factors such as materials availability, toxicity, cost, recyclability, thermal stability, chemical and mechanical properties, and ease of fabrication become important for making viable technologies. Several silicide alloys were identified that have the potential to fulfill these requirements. These materials are of interest due to their abundancy in earth’s crust (e.g., silicon), non-toxicity, and good physical and chemical properties. In this paper, an overview of the silicide thermoelectrics from traditional alloys to advanced material structures is presented. In addition, some of the most effective approaches as well as fundamental physical concepts for designing and developing efficient thermoelectric materials are presented and future perspectives are discussed.}, number={5}, journal={JAPANESE JOURNAL OF APPLIED PHYSICS}, author={Nozariasbmarz, Amin and Agarwal, Aditi and Coutant, Zachary A. and Hall, Michael J. and Liu, Jie and Liu, Runze and Malhotra, Abhishek and Norouzzadeh, Payam and Oeztuerk, Mehmet C. and Ramesh, Viswanath P. and et al.}, year={2017}, month={May} }
 @article{suarez_nozariasbmarz_vashaee_ozturk_2016, title={Designing thermoelectric generators for self-powered wearable electronics}, volume={9}, ISSN={["1754-5706"]}, DOI={10.1039/c6ee00456c}, abstractNote={Body wearable sensors and electronics for health and environment monitoring are becoming increasingly popular as their functionality increases. Thermoelectric generators (TEGs) are of interest to make these wearables self-powered by making them rely entirely on the heat harvested from the human body. The challenge with using thermoelectrics on the human body is the large thermal resistances experienced at the skin/TEG and TEG/ambient interfaces. These parasitics can be potentially so large that they can dominate the device performance. Therefore, it is critical to have accurate models to predict the device performance considering material properties, module design and parasitics. In this paper, we present a computationally efficient, quasi three-dimensional TEG model and use this model to explore the design criteria for current state-of-the-art rigid TEG modules as well as prospective flexible modules for body wearable applications. We show the impact of the properties of the thermoelectric material, module design and dimensions, heat spreaders, filler material, heat sink and skin contact resistance on device performance. We also identify the significance of material thermal conductivity over the Seebeck coefficient and electrical resistivity in improving the output power for wearable applications. For flexible TEGs, we identify the thermal conductivity of the filler material as one of the critical parameters that need to be taken into consideration for optimal performance. Finally, the model was used to design a custom TEG with improved material properties and device design. The measurements indicate a nearly 3× improvement in power output over a commercial TEG with similar area as successfully predicted by the calculations.}, number={6}, journal={ENERGY & ENVIRONMENTAL SCIENCE}, author={Suarez, Francisco and Nozariasbmarz, Amin and Vashaee, Daryoosh and Ozturk, Mehmet C.}, year={2016}, pages={2099–2113} }
 @article{gurarslan_yu_su_yu_suarez_yao_zhu_ozturk_zhang_cao_2014, title={Surface-Energy-Assisted Perfect Transfer of Centimeter-Scale Mono layer and Few-Layer MoS2 Films onto Arbitrary Substrates}, volume={8}, ISSN={["1936-086X"]}, DOI={10.1021/nn5057673}, abstractNote={The transfer of synthesized 2D MoS2 films is important for fundamental and applied research. However, it is problematic to translate the well-established transfer processes for graphene to MoS2 due to different growth mechanisms and surface properties. Here we demonstrate a surface-energy-assisted process that can perfectly transfer centimeter-scale monolayer and few-layer MoS2 films from original growth substrates onto arbitrary substrates with no observable wrinkles, cracks, and polymer residues. The unique strategies used in this process include leveraging the penetration of water between hydrophobic MoS2 films and hydrophilic growth substrates to lift off the films and dry transferring the film after the lift off. This is in stark contrast with the previous transfer process for synthesized MoS2 films, which explores the etching of the growth substrate by hot base solutions to lift off the films. Our transfer process can effectively eliminate the mechanical force caused by bubble generations, the attacks from chemical etchants, and the capillary force induced when transferring the film outside solutions as in the previous transfer process, which consists of the major causes for the previous unsatisfactory transfer. Our transfer process also benefits from using polystyrene (PS), instead of poly(methyl methacrylate) (PMMA) that was widely used previously, as the carrier polymer. PS can form more intimate interaction with MoS2 films than PMMA and is important for maintaining the integrity of the film during the transfer process. This surface-energy-assisted approach can be generally applied to the transfer of other 2D materials, such as WS2.}, number={11}, journal={ACS NANO}, author={Gurarslan, Alper and Yu, Yifei and Su, Liqin and Yu, Yiling and Suarez, Francisco and Yao, Shanshan and Zhu, Yong and Ozturk, Mehmet and Zhang, Yong and Cao, Linyou}, year={2014}, month={Nov}, pages={11522–11528} }