This paper critically reviews the electromagnetic advantages of altering the dielectric substrate section of the antenna as opposed to the conducting elements. Changing the dielectric has been used to improve the bandwidth, e-ciency and gain of antennas. Heterogeneous substrates have also been employed to lower the efiective permittivity, suppress surface waves for high indexed substrate materials and reduce mutual coupling. In the second half of this paper, 3-D printing has been used to create substrates with reduced material consumption for a lightweight ∞exible wearable antenna. Consumer demand for small devices with wireless connectivity has put increasing pressure on antenna engineers to improve electromagnetic performance in smaller packages. These design constraints are further exacerbated by increasing demand for improved bandwidth, e-ciency and frequency coverage. Including an additional degree of design freedom by manipulating the substrate shape and properties can help address these challenges. These synthetic substrates are very di-cult to manufacture using conventional technologies. Complex 3-D printed geometries can easily be manufactured from computer aided design models that can be exported directly from electromagnetic simulation software. 3-D printing allows the geometry to be varied in all three dimensions, therefore printed cavities of various shapes and sizes can lead to a smooth or discrete change in the efiective permittivity. With the latest advances in additive manufacturing and 3-D printing, the antenna and radiofrequency designer will be able to control the local efiective permittivity and the substrate shape to gain electromagnetic advantages. Section 1 of this paper reviews the advantages of using heterogeneous substrates. Section 2 investigates the minimisation of the substrate volume. Section 3 details how these samples can be manufactured using 3-D printing. Conclusions are drawn in Section 4. 1.1. Control of Surface Waves and Current Modes Microstrip antennas are light, low proflle, conformal, compact structures which are normally fabricated on a homogeneous substrate. They can be regarded as a dielectric fllled parallel plate waveguide radiating at discontinuities (1,2). The size of an antenna can be easily reduced by using a dielectric with a high-valued permittivity but this also increases the energy in the surface wave modes (3). These surface waves decrease the e-ciency of the antenna and also cause interference with the radiation pattern by getting difiracted from the edges of the flnite sized ground plane (4). These detrimental efiects can therefore be reduced by suppression of surface wave modes. Heterogeneous substrates have been utilised, for a circular microstrip antenna, to completely suppress the surface waves caused by TM0 mode, which is the main cause of surface wave radiation for thin substrate microstrip antennas (4). The