7 research outputs found
âWhatever is Worth Doing At All, is Worth Doing WellââJust War Thinkers: From Cicero to the 21st Century
Analytical expressions for inductances of 3D air core inductors for integrated power supply
This work presents analytical expressions for the DC inductance of 3D air core inductors with circular cross section pillars (CCSP) and rectangular cross section pillars (RCSP). We consider the following four types of inductor structures: (1) a toroid with CCSP; (2) a toroid with RCSP; (3) a solenoid with RCSP; and (4) a solenoid with CCSP. For each type, a unique analytical model is developed for obtaining DC inductance. High frequency (1-100 MHz) effects on inductance are also discussed. The inductance values predicted by the proposed analytical models of the first three types of inductor structures are in an acceptable agreement with numerical Finite Element Analysis (FEA) solutions, where the maximum difference is 7.3%. Also, our analytical model for the fourth type inductor reduces the error, when correlated with FEA inductance value, up to 6Ă compared to previously published models. A comparison of results using proposed analytical expressions with published measured values as well as our measurement data demonstrates error ranging from 0.5 to 16.2%, while conventional formulae show errors of up to 143%. The results of the proposed models could serve as a good initial estimate for power supply on chip (PwrSoC) and power supply in package (PSiP) applications
Negative gauge factor piezoresistive composites based on polymers filled with MoS2 nanosheets
Nanocomposite strain sensors, particularly those consisting of polymerâgraphene composites, are increasingly common and are of great interest in the area of wearable sensors. In such sensors, application of strain yields an increase in resistance due to the effect of deformation on interparticle junctions. Typically, widening of interparticle separation is thought to increase the junction resistance by reducing the probability of tunnelling between conducting particles. However, an alternative approach would be to use piezoresistive fillers, where an applied strain modifies the intrinsic filler resistance and so the overall composite resistance. Such an approach would broaden sensing capabilities, as using negative piezoresistive fillers could yield strain-induced resistance reductions rather than the usual resistance increases. Here, we introduce nanocomposites based on polyethylene oxide (PEO) filled with MoS2 nanosheets. Doping of the MoS2 by the PEO yields nanocomposites which are conductive enough to act as sensors, while efficient stress transfer leads to nanosheet deformation in response to an external strain. The intrinsic negative piezoresistance of the MoS2 leads to a reduction of the composite resistance on the application of small tensile strains. However, at higher strain the resistance grows due to increases in junction resistance. MoS2âPEO composite gauge factors are approximately â25 but fall to â12 for WS2âPEO composites and roughly â2 for PEO filled with MoSe2 or WSe2. We develop a simple model, which describes all these observations. Finally, we show that these composites can be used as dynamic strain sensors