A apparatus for controlling heat transfer between portions of a substrate is provided. The apparatus includes a substrate including at least part of a hydraulic circuit, the hydraulic circuit including a plurality of microconduits, the plurality of microconduits including a first microconduit and a second microconduit. The apparatus further includes a liquid metal flowing through the hydraulic circuit and a magnetic field configured to selectively direct the flow of the liquid metal between the plurality of microconduits. The flow of the liquid metal through the hydraulic circuit transfers heat between a first portion of the substrate and the liquid metal.