In present-day high-performance electronic components, the generated heat loads result in unacceptably high junction temperatures and reduced component lifetimes. Thermoelectric modules can, in principle, enhance heat removal and reduce the temperatures of such electronic devices. However, state-of-the-art bulk thermoelectric modules have a maximum cooling flux qmax of only about 10 W cm−2, while state-of-the art commercial thin-film modules have a qmax <100 W cm−2. Such flux values are insufficient for thermal management of modern high-power devices. Here we show that cooling fluxes of 258 W cm−2 can be achieved in thin-film Bi2Te3-based superlattice thermoelectric modules. These devices utilize a p-type Sb2Te3/Bi2Te3 superlattice and n-type δ-doped Bi2Te3−xSex, both of which are grown heteroepitaxially using metalorganic chemical vapour deposition. We anticipate that the demonstration of these high-cooling-flux modules will have far-reaching impacts in diverse applications, such as advanced computer processors, radio-frequency power devices, quantum cascade lasers and DNA micro-arrays.

Despite many potential applications, miniature mass spectrometers have had limited adoption in the field due to the tradeoff between throughput and resolution that limits their performance relative to laboratory instruments. Recently, a solution to this tradeoff has been demonstrated by using spatially coded apertures in magnetic sector mass spectrometers, enabling throughput and signal-to-background improvements of greater than an order of magnitude with no loss of resolution. This paper describes a proof of concept demonstration of a cycloidal coded aperture miniature mass spectrometer (C-CAMMS) demonstrating use of spatially coded apertures in a cycloidal sector mass analyzer for the first time. C-CAMMS also incorporates a miniature carbon nanotube (CNT) field emission electron ionization source and a capacitive transimpedance amplifier (CTIA) ion array detector. Results confirm the cycloidal mass analyzer's compatibility with aperture coding. A >10× increase in throughput was achieved without loss of resolution compared with a single slit instrument. Several areas where additional improvement can be realized are identified. Graphical Abstract ᅟ.

As such, metal contacts play an important role for thin-film thermoelectric (TE) devices, especially in high heat-flux applications (e.g., chip cooling) where low contact resistivity (ρ C ) is critical to device performance. [15][16][17] Recent work [18] has demonstrated low electrical contact resistivity ρ C in the range 1-2 × 10 −6 Ω cm 2 in TE modules based on (Bi,Sb) 2 Te 3 superlattices using the evaporation of Cr/Ni/ Au to fabricate metal electrodes. For thinfilm thermoelectric modules with the TE thickness <2 µm, further reduction of ρ C to 10 −8 Ω cm 2 is needed for the contact resistivity to be a small fraction of the resistivity of the thermoelectric element itself. [18] Creating such low contact resistivities is challenging from a fabrication perspective, [19] but also because little is known about the fundamental properties of metal contacts to these materials. For example, even basic properties such as the atomic and electronic structure of the metal/TE interface are largely unknown. This makes it difficult to optimize the contact resistivity and to establish the fundamental limits [20] that are possible. To address this challenge, we present an integrated theoretical and experimental effort toward understanding the limits of low-ρ C in realistic metal contacts to advanced TE materials. We present a new multiscale theoretical approach combining ab initio calculations and continuum mesoscopic models to investigate the structural, electronic, and transport properties of electrical contacts to novel TE materials used in thin-film, superlattice V-telluride devices. We show that the nature of these semiconductor materials leads to unusual contact properties, such as strong n-type doping near the interface and interfacial atomic dipoles that completely determine the band bending. We predict that significant improvement over previously reported experimental data is possible, and we present new experimental data that demonstrate a 100-fold reduction in contact resistivity. Detailed atomistic spatially resolved measurements of the new contacts show that additional improvement should be possible. Importantly, we demonstrate that the reduction in contact resistivity can be harnessed to improve the thermoelectric efficiency of cooling modules.To understand the electrical properties of contacts to (Bi,Sb) 2 Te 3 materials and their realistic low ρ C limit we carried out a series of large scale ab initio calculations of the Sb 2 Te 3 -Cr V-telluride superlattice thin films have shown promising performance for on-chip cooling devices. Recent experimental studies have indicated that device performance is limited by the metal/semiconductor electrical contacts. One challenge in realizing a low resistivity contact is the absence of fundamental knowledge of the physical and chemical properties of interfaces between metal and V-telluride materials. This study presents a combination of experimental and theoretical efforts to understand, design, and harness low resistivity contacts to V-tellurides. Ab initio calculations a...

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Over 2.5 billion people do not have access to safe and effective sanitation. Without a sanitary sewer infrastructure, selfcontained modular systems can provide solutions for these people in the developing world and remote areas. Our team is building a better toilet that processes human waste into burnable fuel and disinfects the liquid waste. The toilet employs energy harvesting to produce electricity and does not require external electrical power or consumable materials.RTI has partnered with Colorado State University, Duke University, and Roca Sanitario under a Bill & Melinda Gates Foundation Reinvent the Toilet Challenge (RTTC) grant to develop an advanced stand-alone, self-sufficient toilet to effectively process solid and liquid waste. The system operates through the following steps: 1) Solid-liquid separation, 2) Solid waste drying and sizing, 3) Solid waste combustion, and 4) Liquid waste disinfection. Thermoelectric energy harvesting is a key component to the system and provides the electric power for autonomous operation. A portion of the exhaust heat is captured through finned heat-sinks and converted to electricity by thermoelectric (TE) devices to provide power for the electrochemical treatment of the liquid waste, pumps, blowers, combustion ignition, and controls.