| Skin is the largest organ in the human body,that directly contact with the outside environment.Chronic skin wounds are usually caused by psychological stress,diabetes,or venous skin ulcers etc.In clinical practice,electrical stimulation is a safe,non-invasive,side-effect free treatment for chronic skin wounds,and has a broad market.There has been developed several electrical stimulation therapy instruments(ESTIs)such as medical,domestic,and wearable types.Among them,the wearable ESTIs have some advantages such as small size,low power consumption,portability,and gain many attentions from both academia and industry.At present,batteries are used to power the wearable ESTIs,that exist problems such as frequent battery replacement or charging.How to harvest the human body energy to power ESTIs has become one of the main research directions in the field of medical devices.Human body thermal energy is a long-term and sustained energy source.The thermoelectric generator is used to fit the human skin to harvest the human body thermal energy to power wearable electronic devices,forming a self-powered ESTI.However,due to the small temperature difference between the human body and the environment,it is necessary to improve the temperature gradient of the thermoelectric generator.Although the use of a heat sink can increase the temperature gradient of the thermoelectric generator,it will increase the overall volume and weight of the device and make it inconvenient to carry.In response to the above challenges,this research conducted in this work are as followings:(1)The radiative cooling thin films such as poly(vinylidene fluoride-co-hexafluoropropene)(P(Vd F-HFP))with a thickness of approximately 800μm and polytetrafluoroethylene(PTFE)have been prepared and attached to the cold end of the thermoelectric generator,and the output power is61.95μW and 60.352μW respectively.Compared with the thermoelectric generator without radiative cooling films,under the same heat source,the output power is increased by 14.99% and 12.03%,respectively.(2)ANSYS and MATLAB are used to construct a steady-state thermoelectric generator model,and compared with the actual test data,the deviation was as low as 6.52%.A theoretical model of the thermoelectric generator device using human skin as the heat source combined with the radiative cooling thin films is further constructed using MATLAB,and compared with the measured data,the deviation is not more than 9%.(3)A low-power self-powered electrical stimulation wound healing system is designed,including a power management circuit,a pulse generator,and a Bluetooth module.The input voltage of the power management circuit can be as low as 20 m V and the output voltage is 2.5V.To meet the low power consumption requirement of the system,the low-power working modes of the pulse generator and the Bluetooth module are designed.The pulse generator outputs an electrical stimulation signal with a frequency of 1Hz,a current of 50μA,and a duty ratio of 50% in the form of single-phase pulse waveform.(4)The analysis has verified the feasibility of the self-powered electrical stimulation wound healing system.The total periodic power consumption(per 10 minutes)of the system energy consumption module(the electrical stimulation device)is 42.322 m J.Among them,the average power of the pulse generator is about 63.75μW which consumes 38.25 m J for 10 min continuous operation,and 4.072 m J for the Bluetooth module to work for 1 time(including 1min broadcast events and 1min connection events).The 97.2m J energy stored in the energy storage circuit is enough to support the system,achieving the energy balance of the self-powered electrical stimulation wound healing system.The thermoelectric generator module takes about 25 min of power generation to support the work of the overall system circuit.In a real sense,the system realizes the use of human energy for electrical stimulation wound healing treatment through the thermoelectric energy harvester. |
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