A variety of samples, including animals, humans, cadavers, and explants, has been extensively employed in the investigation of the similarities between materials and human tissue [1]. These studies provide an initial characterisation of human tissues. However, ethical considerations may arise from the use of such samples, and their effectiveness is constrained by a number of limitations. Accurate measurements cannot be obtained from cells that have already died or undergone necrosis. Furthermore, the human body's physiology is subject to constant change, which represents the most restrictive limitation. Moreover, due to the inherent variability of human physiology, in vivo measurements are susceptible to fluctuations in both inter- and intra-subject variability over a relatively short period of time [2], [3]. To overcome these limitations, phantoms have been developed. They offer a number of advantages with regard to the measurement repeatability and reproducibility, long-term stability, cost-effectiveness and ease of storage. The use of a phantom, which may be anthropomorphic, enables the design and control of characteristics such as age, gender, physiology, physical status, and potential pathology of the target tissues [1]. Phantoms are frequently employed across a wide range of applications, including biomedical imaging, sensor validation, calibration of measurement devices, and the assessment of medical equipment safety [4], [5], [6], [7]. Such phantoms are commonly developed using biological materials, such as vegetables or gelatinous substances filled with conductive particles [8], [9]. However, these materials may exhibit a lack of stability over time and poor mechanical properties. The use of materials such as silicones, elastomers and filled polymers can significantly enhance mechanical properties and improve long-term stability [10].

The aim of this review is to provide a comprehensive overview of the materials and design methods used in the development of phantoms that mimic the electrical properties of human tissues for a wide range of applications, from low to high frequency measurements. The materials employed in phantom fabrication are evaluated based on their electrical properties, mechanical strength, long-term stability, and environmental impact. Despite the extensive development of such phantoms, ethical concerns may arise with regard to the materials and fillers used to replicate the properties of living tissues. Consequently, this review focuses on the use of eco-friendly materials, with the employment of non-environmentally friendly materials being explicitly acknowledged where applicable. This paper is structured as follows: section 2 presents an overview of the electrical and mechanical properties of living tissues, which serve as essential criteria for phantom development. The section starts with a review of the electrical properties of living tissues and examples of relevant measurement devices, followed by a discussion of their mechanical properties and the techniques used for their assessment. Section 3 then details the methods and materials employed in phantom design, supported by examples from the literature. The materials highlighted throughout the literature are summarised in Table 1, categorised according to their role in phantom development (mechanical supports or fillers). Finally, a comprehensive discussion is presented on the advantages and limitations of the materials reviewed.