Silver nanowire arrays embedded inside polycarbonate templates are investigated as a viable thermal interface material for electronic cooling applications. The composite shows an average thermal diffusivity value of 1.89×10−5 m2 s−1, which resulted in an intrinsic thermal conductivity of 30.3 W m−1 K−1. The nanowires’ protrusion from the film surface enables it to conform to the surface roughness to make a better thermal contact. This resulted in a 61% reduction in thermal impedance when compared with blank polymer. An ∼30 nm Au film on the top of the composite was found to act as a heat spreader, reducing the thermal impedance further by 35%. A contact impedance model was employed to compare the contact impedance of aligned silver nanowire-polymer composites with that of aligned carbon nanotubes, which showed that the Young’s modulus of the composite is the defining factor in the overall thermal impedance of these composites.
The recent European Commission REACH (Registration, Evaluation and Authorisation of Chemicals) policy outlines a plan for toxicological testing by using alternative non-animal in vitro methods. In this context, there is a need to develop and standardise high-throughput screening (HTS) methods for studying the cytotoxicity induced by chemicals. Electrochemical impedance spectroscopy (EIS) can be considered as a complementary technique to alternative in vitro testing for studying cell adhesion to the substrate, and can give real-time and kinetic information on cell responses to a toxicant. This paper describes the development of a home-made chip based on impedance spectroscopy, and its application in studying the kinetics of BALB/3T3 cell adhesion and the cellular responses to a toxic product as a function of time. Concentrations of sodium arsenite, ranging from 10μM up to 1000μM, were tested in the system, and the results were compared with those obtained with standard protocols used to study basal cytotoxicity induced by chemicals in the BALB/3T3 cell line. The results show that the sensitivity of the developed chip was better than that with the MTT test, with the additional advantages of online monitoring.
This work presents the thermal property study of single wall and multi wall carbon nanotubes (SWCNT and MWCNT) both in their purified and unpurified forms introduced to silicone elastomer to enhance the thermal diffusivity of this industrial polymer. An increase in thermal diffusivity was observed for incremental loading of both purified and unpurified single wall and multiwall CNT in epoxy at different percentages. An increase of thermal diffusivity as high as 130% was achieved for ∼2 wt% loading of both single wall and multi wall nanotubes. Electrical conductivity measurements showed a percolation threshold for 2% loading of multiwall CNT, below which the nanotube-epoxy composite behaved as an insulator — this is a key property for applications where electrical isolation is required. For single wall CNT-epoxy composite all the samples showed high resistance to the conduction of current. Thermal impedance measurements showed a strong dependency of contact resistance with percentage loading. Finally, the feasibility of deploying carbon nanotube-polymer composites as practical thermal interface materials for electronics thermal management is discussed.
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