Dynamic rectification in a thermal diode based on fluid-solid interfaces: Contrasting behavior of soft materials and fluids

We have used molecular dynamics simulations to demonstrate that significant rectification is possible in nano-devices by manipulating solid-fluid interfaces between a thin solid wall and a soft material. In addition, the nature of the rectification is opposite to that for a solid wall and a simpler polar fluid (e.g., water). This thus opens the possibilities of reversing the direction of rectification in a nano-device which could lead to more precise control of heat transfer rates. Our simulations also show that surface modifications of the type introduced here can lead to over six fold increase in heat transfer rates in nano-devices. Dissipating heat from increasingly miniaturized semi-conductors of the future will become increasingly important since size limitations are often dictated by heat dissipation rates. These results also point to some other exciting practical applications. If the outside wall of a house were made hydrophilic, during hot summer days when the intent is to reduce heat transfer from the ambient (Ta > Tin), a small polar fluid like water could be introduced between the two walls. During nights, in order to cool the house (when Tin > Ta) water could be replaced by a less volatile soft material to enhance heat transfer. Thus, the same wall would demonstrate significant rectification in both cases but with different fluids.