Abstract
Small-scale energy harvesting thermoelectric generators could replace bulky batteries completely when in conjunction with a supercapacitor for biomedical devices. Organic material is cost efficient, flexible and easily processed but has poor thermoelectric properties. Recent studies have investigated the combination of inorganic and organic materials for thermoelectric materials in an attempt to improve the figure of merit, Seebeck coefficient and power factor. This meta-study examines the most effective ratio of PEDOT: PSS to Bi2Te3 thermoelectric material by analysing the Seebeck coefficient, electrical and thermal conductivity, the power factor and figure of merit for varying weight-for-weight percentage of PEDOT: PSS material. This paper also assesses the viability of hybrid thermoelectric materials with a focus on the synthesis process. The parameter of the thermal gradient found in the human body was used; approximated to 32-37°C from the human body to the ambient temperature of ~300 K. It was found that the peak in electrical conductivity was between 90%―96% PEDOT: PSS material. From this the optimal ratio of PEDOT: PSS to Bi2Te3 is between 90%―96% PEDOT: PSS material since the Seebeck coefficient decrease with increase organic percentage smoothly. Overall, this study suggests the use of an organic: inorganic hybrid TEG, coupled with a supercapacitor, is a commercially viable device for a variety of implantable biomedical devices.
Highlights
Thermoelectric generator Thermoelectric Organic Thermoelectric generator Figure of merit Power factor Poly(3,4-ethylenedioxythiophene): Poly(styrenesulfonate) Polyaniline nanofibers Poly (3-hexylthiophene) Electrical double layer capacitor Vertical graphene nanosheets Graphene quantum dot Lithium ion batteries that are used for biomedical devices, long-lived, powerful and stable, are still large and need regular replacement throughout the life of the patient
There is an assigned number to distinguish how good a material is as a thermoelectric material; it is defined as the figure of merit (FOM)
Keywords which were used in the database searches included; thermoelectric generator, human energy harvesting, human body heat, surface energy harvesting, thermodynamic pacemakers, biosensors, organic thermoelectric generators, inorganic thermoelectric generators, PEDOT: PSS, Bi2Te3, hybrid TEGs and organic supercapacitors
Summary
Lithium ion batteries that are used for biomedical devices, long-lived, powerful and stable, are still large and need regular replacement throughout the life of the patient Biomedical devices such as hearing aids and pacemakers need a power source typically upwards of 2.2V [1], depending on the use of the device, patients pacing threshold, or safety margin of the device. The batteries are of considerable size, typically occupying half the total volume of the pacemaker to reduce the number of times removal and replacement is required [1] This makes the whole unit large enough to be uncomfortable and cumbersome. If the battery were to be replenished continuously by an energy harvesting device, the need to remove, replace and limit the voltage of the battery would be negated One such energy harvesting device is the thermoelectric generator (TEG). The FOM (notated at ZT) of a material has three controlling factors; a high Seebeck coefficient, S, a high electrical conductivity, σ, and a low thermal conductivity, κ
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