Showing papers by "Daryoosh Vashaee published in 2020"
TL;DR: An overview of wearables market trends, different active and passive methods of body energy harvesting for powering low-consumption electronic devices are introduced, and challenges of device fabrication are discussed.
323 citations
TL;DR: In this paper, a flexible thermoelectric generators (TEGs) employing eutectic gallium indium (EGaIn) liquid metal interconnects encased in a novel, high thermal conductivity elastomer.
100 citations
TL;DR: In this article, a quasi-3D analytical model was developed and used to optimize the material and device parameters of wearable TEGs to maximize the temperature differential across the TEG while not compromising the body comfort.
60 citations
TL;DR: In vivo results showed a significant enhancement in the bioactivity of the nanocomposite coated AZ91 implant compared to the uncoated control implant and a reduction in the corrosion rate of the coated implants resulted in an improved new bone formation and reduced inflammation in the interface of the implants and the surrounding tissue.
Abstract: Magnesium (Mg) alloys are being investigated as a biodegradable metallic biomaterial because of their mechanical property profile, which is similar to the human bone. However, implants based on Mg alloys are corroded quickly in the body before the bone fracture is fully healed. Therefore, we aimed to reduce the corrosion rate of Mg using a double protective layer. We used a magnesium-aluminum-zinc alloy (AZ91) and treated its surface with micro-arc oxidation (MAO) technique to first form an intermediate layer. Next, a bioceramic nanocomposite composed of diopside, bredigite, and fluoridated hydroxyapatite (FHA) was coated on the surface of MAO treated AZ91 using the electrophoretic deposition (EPD) technique. Our in vivo results showed a significant enhancement in the bioactivity of the nanocomposite coated AZ91 implant compared to the uncoated control implant. Implantation of the uncoated AZ91 caused a significant release of hydrogen bubbles around the implant, which was reduced when the nanocomposite coated implants were used. Using histology, this reduction in the corrosion rate of the coated implants resulted in an improved new bone formation and reduced inflammation in the interface of the implants and the surrounding tissue. Hence, our strategy using a MAO/EPD of a bioceramic nanocomposite coating (i.e., diopside-bredigite-FHA) can significantly reduce the corrosion rate and improve the bioactivity of the biodegradable AZ91 Mg implant.
43 citations
TL;DR: In this paper, two material systems, namely MnSb and CrSb, which are similar in many aspects except that the former is ferromagnetic and the latter antiferromagnetic (AFM) magnons interact differently with the carriers and generate different amounts of drag-thermopower.
Abstract: The extension of magnon electron drag (MED) to the paramagnetic domain has recently shown that it can create a thermopower more significant than the classical diffusion thermopower resulting in a thermoelectric figure-of-merit greater than unity. Due to their distinct nature, ferromagnetic (FM) and antiferromagnetic (AFM) magnons interact differently with the carriers and generate different amounts of drag-thermopower. The question arises of whether the MED is stronger in FM or in AFM semiconductors. Two material systems, namely MnSb and CrSb, which are similar in many aspects except that the former is FM and the latter AFM, were studied in detail, and their MED properties were compared. Three features of AFMs compared to FMs, namely double degeneracy of the magnon modes, higher magnon group velocity, and longer magnon relaxation time, can lead to enhanced first-order MED thermopower. One effect, magnon–electron relaxation, leads to a higher second-order effect in AFMs that reduces the MED thermopower. However, it is generally expected that the first-order effect dominates and leads to a higher drag thermopower in AFMs, as seen in this case study.
28 citations
TL;DR: In this article, the authors developed composite scaffolds of HA-barium titanate (BT) by cold isostatic pressing and sintering to improve the physical, mechanical, electrical and biological properties of pure HA.
23 citations
TL;DR: In this article, a theoretical model for magnon-bipolar carrier drag thermopower is derived based on the magnoncarrier interaction lifetimes, which predicts that the bipolar carrier drag becomes independent of both the carrier and magnon relaxation times.
Abstract: Quantized spin-wave known as magnon, a bosonic quasiparticle, can drag electrons or holes via s-d exchange interaction and boost the thermopower over the conventional diffusive thermopower. P-type magnon-drag thermopower has been observed in both ferromagnetic and antiferromagnetic metallic and degenerate semiconductors. However, it has been less reported for intrinsic or $n$-type magnetic semiconductors; therefore, the impact of magnon-bipolar carrier drag on thermopower has remained unexplored. Here, a theoretical model for magnon-bipolar carrier drag thermopower is derived based on the magnon-carrier interaction lifetimes. The model predicts that the bipolar carrier drag thermopower becomes independent of both the carrier and magnon relaxation times. A proof of concept experiment is presented that confirms this prediction. We also report the observation of magnon-carrier drag thermopower in n-type and intrinsic ferromagnetic semiconductors experimentally. The p-type antiferromagnetic MnTe is doped with different amounts of Cr to produce nondegenerate and n-type semiconductors of various carrier concentrations. Cr dopants have a donor nature and create ferromagnetic-antiferromagnetic clusters due to the $\mathrm{C}{\mathrm{r}}^{3+}$ oxidation state. Heat capacity measurements confirm the presence of magnons in Cr-doped MnTe. It is shown that the magnon-drag thermopower is significantly reduced for 3%--5% Cr-doped samples due to bipolar drag effects and becomes negative for 14% and 20% Cr-doped MnTe due to dominant magnon-electron drag thermopower.
18 citations
TL;DR: The in vitro biological analysis using human osteoblast cells reveals that scaffolds are biocompatible with adequate ALP activity, and indicates that the HA/ZnO scaffolds possess higher compressive strength, fracture toughness, and density—but lower hardness—when compared to the pure HA scaffolds.
17 citations
TL;DR: In vitro biological analysis using human osteoblast cells reveals that scaffolds are biocompatible with adequate ALP activity and obtained results indicate that the HA/ MnO2 scaffolds possess higher compressive strength, toughness, hardness, and density when compared to the pure HA scaffolds.
13 citations
TL;DR: In this article, the authors present experimental evidence for the simultaneous existence of the magnons and spin-state transition contributions to the heat capacity in ferromagnetic (FM) Cr-doped MnTe (Tc ∼ 280 K), where the magnon heat capacity is attributed to the observed magnon-bipolar carrier-drag thermopower.
Abstract: We present experimental evidence for the simultaneous existence of the magnons and spin-state transition contributions to the heat capacity in ferromagnetic (FM) Cr-doped MnTe (Tc ∼ 280 K), where the magnon heat capacity is attributed to the observed magnon-bipolar carrier-drag thermopower. The pristine antiferromagnetic (AFM) MnTe shows only a magnon-induced peak in the heat capacity near the Neel temperature, TN ∼ 307 K. However, Cr-doped MnTe shows a magnon-contributed heat capacity peak at ∼293 K with an additional peak in the deep paramagnetic domain near 780 K. Temperature-dependent magnetic susceptibility reveals that Cr-doping initially creates low-spin (LS) state Mn2+ ions into MnTe near and below TN due to a higher crystal field induced by Cr ions. Above 400 K, LS Mn2+ ions start converting into high-spin (HS) Mn2+ ions. The LS-to-HS transition of Mn2+ leads to an excess entropy and hence excess heat capacity contribution in the system. Temperature-dependent X-ray diffraction (XRD) and magnetic field-dependent susceptibility (M-H) confirmed no presence of any structural changes and magnetic polaron, respectively. Both XRD and M-H ensure that the peak of the heat capacity in the paramagnetic domain is originated solely by the spin-state transition. The heat capacity vs temperature was calculated to explain the contribution of each component, including the ones due to the phonons, magnons, spin-transition, Schottky anomaly, and lattice dilation. With the recent advances in spin-caloritronics extending the spin-based effects from magnetic to paramagnetic materials, the data from the heat capacity can play a crucial role to probe the presence of different phenomena, such as paramagnon-carrier-drag and spin-entropy thermopowers.
11 citations
TL;DR: In this paper, an ASTM F2581 nanostructured stainless steel was fabricated by two different powder metallurgy routes; Hot Powder Forging (HPF) and Binder Assisted Extrusion (BAE) methods.
TL;DR: In this article, the influence of fabrication processes on the thermoelectric properties of CoSb3 skutterudite was investigated using a grain boundary potential barrier mechanism, which is consistent with the systematic increase of the carrier concentration upon increasing the Cu0.6Ni0.4 content.
TL;DR: The results showed that the HA/ZnO/Pd scaffolds possess higher compressive strength and toughness and lower microhardness and density compared to the pure HA (H0) scaffolds.
Abstract: The purpose of this study was to produce and characterize Hydroxyapatite/Zinc Oxide/Palladium (HA/0.05 wt% ZnO/0.1 wt% Pd) nanocomposite scaffolds and study their mechanical and antibacterial properties, biocompatibility and bioactivity. The initial materials were developed using sol-gel and precipitation methods. Scaffolds were characterized using atomic absorption analysis (AA), scanning electron microcopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM), atomic force microscopy (AFM) and Brunauer−EmmeS−Teller (BET) method. Furthermore, the bioactivity of scaffolds in simulated body fluid (SBF) and the interaction of dental pulp stem cells (DPSCs) with the nanocomposite scaffolds were assessed. Our results showed that the HA/ZnO/Pd (H1), HA/ZnO/Pd coated by 0.125 g chitosan (H2) and HA/ZnO/Pd coated by 0.25 g chitosan (H3) scaffolds possess higher compressive strength and toughness and lower microhardness and density compared to the pure HA (H0) scaffolds. Immersion of samples in SBF showed the deposition of apatite on the surface of the scaffolds. The biocompatibility assay indicated lower cell proliferation on the H1, H2 and H3 in comparison to the H0. The antibacterial results obtained show a significant impact by loading Pd/ZnO on HA in the deactivation of microorganisms in vitro.
TL;DR: In this paper, the authors reported the experimental realization of a half-Heusler (HH) ternary alloy of CoVSn and characterizations of its thermoelectric properties, which was synthesized by a solid-state reaction of the stoichiometric amounts of the elements via powder metallurgy.
Abstract: Hypothetical half-Heusler (HH) ternary alloy of CoVSn has already been computationally investigated for possible spintronics and thermoelectric applications. We report the experimental realization of this compound and the characterizations of its thermoelectric properties. The material was synthesized by a solid-state reaction of the stoichiometric amounts of the elements via powder metallurgy (30 h mechanical milling and annealing at 900 °C for 20 h) and spark plasma sintering (SPS). The temperature-dependent ternary thermodynamic phase diagram of Co-V-Sn was further calculated. The phase diagram and detailed analysis of the synthesized material revealed the formation of the non-stoichiometry HH CoVSn, mixed with the binary intermetallic phases of SnV3, Co2Sn, and Co3V. The combination of X-ray diffraction, energy-dispersive X-ray spectroscopy, and thermoelectric transport properties confirmed the formation of a multi-phase compound. The analysis revealed the predicted thermoelectric features (zT = 0.53) of the highly doped CoVSn to be compromised by the formation of intermetallic phases (zT ≈ 0.007) during synthesis. The additional phases changed the properties from p- to overall n-type thermoelectric characteristics.
TL;DR: In this article, the effect of glass inclusion, microwave processing, and annealing on the synthesis of high-performance p-type (BixSb1−x)2Te3 nanocomposites, optimized specially for body heat harvesting and body cooling applications, was investigated.
Abstract: Depending on the application of bismuth telluride thermoelectric materials in cooling, waste heat recovery, or wearable electronics, their material properties, and geometrical dimensions should be designed to optimize their performance. Recently, thermoelectric materials have gained a lot of interest in wearable electronic devices for body heat harvesting and cooling purposes. For efficient wearable electronic devices, thermoelectric materials with optimum properties, i.e., low thermal conductivity, high Seebeck coefficient, and high thermoelectric figure-of-merit (zT) at room temperature, are demanded. In this paper, we investigate the effect of glass inclusion, microwave processing, and annealing on the synthesis of high-performance p-type (BixSb1−x)2Te3 nanocomposites, optimized specially for body heat harvesting and body cooling applications. Our results show that glass inclusion could enhance the room temperature Seebeck coefficient by more than 10% while maintaining zT the same. Moreover, the combination of microwave radiation and post-annealing enables a 25% enhancement of zT at room temperature. A thermoelectric generator wristband, made of the developed materials, generates 300 μW power and 323 mV voltage when connected to the human body. Consequently, MW processing provides a new and effective way of synthesizing p-type (BixSb1−x)2Te3 alloys with optimum transport properties.
TL;DR: A detailed theoretical model and experimental study are presented that formulate and prove the existence of a robust ponderomotive force near the interfaces in a granular dielectric material under microwave radiation and offer a novel and simple approach for the synthesis of nanostructured compounds.
Abstract: A detailed theoretical model and experimental study are presented that formulate and prove the existence of a robust ponderomotive force (PMF) near the interfaces in a granular dielectric material ...
TL;DR: In this article, the authors induced linear birefringence and linear dichroism in subwavelength Ag-AgCl films by irradiating with a single low-power linearly polarized laser beam.
Abstract: Silver nanogratings are anisotropic plasmonic nanostructures with potential application in optical components due to their large birefringence and dichroism. We induced linear birefringence and linear dichroism in subwavelength Ag-AgCl films by irradiating with a single low-power linearly polarized laser beam. The laser beam aligns silver nanoparticles in the direction of laser polarization and forms nanograting. We used Stokes parameters to determine linear birefringence and linear dichroism in silver aligned nanostructures. The values of linear dichroism and linear birefringence in silver nanogratings are controllable through manipulating the spatial period of nanogratings. The dispersion characteristic of dichroism and birefringence is also investigated.
01 Jan 2020
TL;DR: This book chapter aims to address the advancement of tissue engineering for different dental hard and soft tissues, such as enamel, dentin, bone, periodontium, oral mucosa, and salivary glands.
Abstract: Tissue engineering is a novel and multidisciplinary field that intends to remake functional, sound tissues and organs to supplant unhealthy or dead tissues. The advancement of tissue engineering for dental tissues is promising, and different dental soft and hard tissues have been regenerated effectively in vitro, utilizing stem cells and scaffolds. In almost any tissue engineering application, there are various challenges and unanswered inquiries that should be settled for further advancements. It is expected that in the next few decades, the field of dentistry will be altered remarkably by the accessibility of novel tissue-engineered products in the dental industry. This book chapter aims to address the advancement of tissue engineering for different dental hard and soft tissues, such as enamel, dentin, bone, periodontium, oral mucosa, and salivary glands. Additionally, challenges in the advancement of tissue engineering and future trends have been summarized in this book chapter.
TL;DR: In this article, the authors present experimental evidence for the simultaneous existence of the magnons and spin-state transition contributions to the heat capacity in ferromagnetic (FM) Cr-doped MnTe (Tc~280K), where the magnon heat capacity is attributed to the observed magnon-bipolar carrier-drag thermopower.
Abstract: We present experimental evidence for the simultaneous existence of the magnons and spin-state transition contributions to the heat capacity in ferromagnetic (FM) Cr-doped MnTe (Tc~280K), where the magnon heat capacity is attributed to the observed magnon-bipolar carrier-drag thermopower. The pristine antiferromagnetic (AFM) MnTe shows only a magnon-induced peak in the heat capacity near the Neel temperature, TN~307K. However, Cr-doped MnTe shows a magnon-contributed heat capacity peak at ~293K with an additional peak in the deep paramagnetic domain near 780K. Temperature-dependent magnetic susceptibility reveals that Cr-doping initially creates low-spin (LS) states Mn2+ ions into MnTe near and below TN due to a higher crystal field induced by Cr ions. Above 400K, LS Mn2+ ions start converting into high-spin (HS) Mn2+ ions. The LS-to-HS transition of Mn2+ leads to an excess entropy and hence excess heat capacity contribution in the system. Temperature-dependent X-ray diffraction (XRD) and magnetic field-dependent susceptibility (M-H) confirmed no presence of any structural changes and magnetic polaron, respectively. Both XRD and M-H ensure that the peak of the heat capacity in the paramagnetic domain is originated solely by the spin-state transition. The heat capacity versus temperature was calculated to explain the contribution of each component, including the ones due to the phonons, magnons, spin-transition, Schottky anomaly, and lattice dilation. With the recent advances in spin-caloritronics extending the spin-based effects from magnetic to paramagnetic materials, the data from the heat capacity can play a crucial role to probe the presence of different phenomena such as paramagnon-carrier-drag and spin-entropy thermopowers.