A novel temperature sensor consisting of a single layer of metal (Ni, Pd, W, or Pt) is constructed. Its configuration challenges a long-established concept and may lead to development of a new category of devices. Reliable two-dimensional mapping of local temperatures is demonstrated using an array of these sensors. These single-metal thermocouples (SMTCs) can be readily applied on flexible substrates or at high temperatures.

To monitor the temperature distribution of a cell and its changes under varied conditions is currently a technical challenge. A variety of non-contact methods used for measuring cellular temperature have been developed, where changes of local temperature at cell-level and sub-cell-level are indirectly calculated through the changes in intensity, band-shape, bandwidth, lifetime or polarization anisotropy of the fluorescence spectra recorded from the nano-sized fluorescent materials pre-injected into the target cell. Unfortunately, the optical properties of the fluorescent nano-materials may be affected by complicated intracellular environment, leading to unexpected measurement errors and controversial arguments. Here, we attempted to offer an alternative approach for measuring the absolute increments of local temperature in micro-Testing Zones induced by live cells. In this method, built-in high-performance micro-thermocouple arrays and double-stabilized system with a stability of 10 mK were applied. Increments of local temperature close to adherent human hepatoblastoma (HepG2) cells were continuously recorded for days without stimulus, showing frequent fluctuations within 60 mK and a maximum increment by 285 mK. This method may open a door for real-time recording of the absolute local temperature increments of individual cells, therefore offering valuable information for cell biology and clinical therapy in the field of cancer research.

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For low-dimensional materials, size effect of a physical property is usually expected to occur when one (or more) of the dimension sizes decreases to that comparable to or smaller than one of the intrinsic characteristic lengths, e.g., the mean free path. We report here an unexpected size effect, that in centimeter-long stripes of 100-nm-thick metallic thin films, a reduction of the absolute value of thermopower occurs when the stripe width is in the order of 30-50 μm, which is 100–1000 times larger than the intrinsic mean free path of the material. When the stripe width is reduced to 1.5 μm, a relative reduction of thermopower up to 35% is measured in some metals. We suggest that the sidewall scattering due to rough edges of these stripes may be the origin of this unexpected phenomenon. The results may be applied to construct novel thermoelectric devices, such as thermocouples made from a single metal film.

Submicrometer dual-stripe temperature sensors made from a single piece of metal thin film (e.g., Pd) are developed. With the narrowest sensor being 900 nm in width, they show sensitivity of 1-2 μV/K for the full range of 10-300 K. The results confirm the size effect in Seebeck coefficient previously observed in microstripe sensors of the same device configuration.