Microthermoelectric generators are miniaturized solid-state energy harvesters which can convert thermal energy into electrical energy in a sustainable manner. Over the last decade, the human body’s core energy has been considered as a promising source to harvest electrical energy through flexible microthermoelectric generators. The potential of the microthermoelectric generator modules to become an alternative power generation technique is not negligible. The flexible thermoelectric generator has the potential to generate sufficient energy for any wireless sensor nodes typically in microwatt-milliwatt range. In this study, a survey of microthermoelectric generator design is comprehensively presented with a specific focus given to the flexible types for wearable applications. The aim of this work is to design a wearable microthermoelectric generator module for ultra-low-power sensor applications with the capability of generating 1.4 V with 2 μW power output. The basic principle of thermoelectric power generator design, fabrication, and some existing challenges discussed. The resultant module was capable of generating the maximum output voltage of 15mV. The difference between the designed module and microfabricated prototype relies on the different material properties of the prepared thin-films with the assumed values, the effect of the flexible substrate material and loss due to parasitic heat flow.