Biomechanical energy harvesting technologies for wearable electronics:Theories and devices

Wearable biomechanical energy harvesting devices have received a lot of attention recently,benefiting from the rapid advancement of theories and devices in the field of the micro electromechanical system(MEMS).They not only fulfil the requirements for powering wearable electronic devices but also provide an attractive prospect for powering self-powered flexible electronic devices when wearing.In this article,we provide a review of the theories and devices of biomechanical energy harvesting technology for wearable applications.Three different forms of biomechanical energy harvesting mechanisms,including the piezoelectric effect,electromagnetic effect,and electrostatic effect,are investigated in detail.The fundamental principle of converting other types of energy from the biomechanical environment into electrical energy,as well as the most commonly-used analytical theoretical models,are outlined for each process.Therefore,the features,properties,and applications of energy harvesting devices are summarized.In addition,the coupled multi-effect hybrid energy harvesting devices are listed,showing the various possibilities of biomechanical energy harvesting devices for serving as sources,sensors,and actuators.Finally,we present perspectives on the future trends of biomechanical energy harvesting devices for wearable electronics applications.

Natural polymers based triboelectric nanogenerator for harvesting biomechanical energy and monitoring human motion

Triboelectric nanogenerator(TENG)has been proved as a promising energy harvester in recent years,but the challenges of exploring economically triboelectric materials still exist and have aroused interests of many researchers.In this paper,chitosan-silk fibroin-airlaid paper composite film(CSA film)was fabricated and then the CSA film based-triboelectric nanogenerator(CSA-TENG)was constructed,which presents an opportunity for natural polymers to be applied in triboelectric materials.Due to the excellent electron donating ability of CSA film,the CSA-TENG can harvest environmental energy with a high efficiency.More importantly,the as-designed CSA film based dual-electrode triboelectric nanogenerator(CSA-D-TENG)is successfully assembled into hand clapper and trampoline to harvest mechanical energies generated by human bodies,it is also capable of monitoring human movement while harvesting biomechanical energies.This work provides a simple and environmental-friendly way to develop TENG for biomechanical energies harvesting and human motion monitoring.

Optimal patching locations and orientations for maximum energy harvesting efficiency of ultrathin flexible piezoelectric devices mounted on heart surface

Flexible piezoelectric energy harvesters(PEHs)have gained lots of attention in recent years,because of their potential biomechanical applications,such as powering implantable devices.Several in vivo animal experiments have demonstrated that the output power of a flexible PEH varies remarkably with patching orientations and locations,but the underlying mechanism remains unclear yet.Herein,an electromechanical model for a flexible PEH installed on a beating heart is proposed,and a concise relationship between the output power of the device and myocardium strain is established.The results demonstrate that the patching orientations have a significant impact on the output power of the PEH,and the optimal patching orientations for all patching locations are approximately 15–20 degree for PEHs mounted on the left ventricle.The simple theoretical method provided here would be universally effective for choosing the optimal patching locations and orientations of flexible PEHs installed on a nonhomogeneous deformed surface.

Free energy calculation of single molecular interaction using Jarzynski's identity method:the case of HIV-1 protease inhibitor system

Jarzynski＇ identity （JI） method was suggested a promising tool for reconstructing free energy landscape of biomolecular interactions in numerical simulations and ex- periments. However, JI method has not yet been well tested in complex systems such as ligand-receptor molecular pairs. In this paper, we applied a huge number of steered molec- ular dynamics （SMD） simulations to dissociate the protease of human immunodeficiency type I virus （HIV-1 protease） and its inhibitors. We showed that because of intrinsic com- plexity of the ligand-receptor system, the energy barrier pre- dicted by JI method at high pulling rates is much higher than experimental results. However, with a slower pulling rate and fewer switch times of simulations, the predictions of JI method can approach to the experiments. These results sug- gested that the JI method is more appropriate for reconstruct- ing free energy landscape using the data taken from experi- ments, since the pulling rates used in experiments are often much slower than those in SMD simulations. Furthermore, we showed that a higher loading stiffness can produce higher precision of calculation of energy landscape because it yields a lower mean value and narrower bandwidth of work distri- bution in SMD simulations.

Lead-free silver niobate microparticles-loaded PDMS composite films for high-performance clip-like hybrid mechanical energy harvesters

A triboelectric nanogenerator(TENG)is a highly potential green energy harvesting technology to power small-scale electronic devices.Enhancing the overall electricity production capacity of TENGs is a primary concern for their utilization as an electricity generator in day-to-day life.Herein,we proposed a lead-free silver niobate(AgNbO_(3)(ANb))microparticles(MPs)-embedded polydimethylsiloxane(PDMS)composite film-based clip-like hybrid nanogenerator(HNG)device,producing an enhanced electrical output from the applied mechanical movements.The ANb MPs with a high dielectric constant were initially synthesized and embedded inside the PDMS polymer matrix.Various HNGs were fabricated utilizing ANb MPs/PDMS composite films/aluminum tape as negative/positive triboelectric films,respectively and operated in contact-separation mode.The electrical output from them was comparatively analyzed to investigate an optimum concentration of the ANb MPs inside the PDMS film.The robust HNG with 5 wt%ANb MPs/PDMS composite film produced the highest electrical output with promising stability.Thereafter,three similar optimized HNGs were fabricated and integrated within a 3D-printed clip-like structure and the electrical output was thoroughly evaluated while combining multiple HNGs as well as from each independent HNG.The clip-like HNG device exhibited an electrical output of 340 V and 20μA that can be further utilized to charge various capacitors and power portable electronics.Owing to the high resilience structure of the clip-like HNG device,it was also demonstrated to harvest biomechanical energy produced by human movements into electricity.The mechanical energy harvesting when the clip-like HNG device was attached to the accelerator pedal of the car and the pedal of a musical piano was successfully demonstrated.

Triboelectric nanogenerators for self-powered neurostimulation

The burgeoning field of soft bioelectronics heralds a new dawn in medical treatment for neurological and psychiatric conditions,presenting innovative methods for the stimulation,inhibition,and precise sensing of neuronal activities.Central to these advancements is the challenge of power supply;devices dependent on traditional batteries face limitations regarding miniaturization and require invasive surgeries for battery replacement.Triboelectric nanogenerators(TENGs),which generate power from biomechanical movements,offer a promising solution for developing self-powered neurostimulation devices without the need for an external power supply.This review delves into recent progress in TENGs,with a focus on their application in selfpowered neurostimulation systems.The utility of TENGs across various nervous systems—including the center,autonomic,and somatic nervous systems—is explored and presented,highlighting the potential for these devices to facilitate neurological treatments.By summarizing TENGs’operational details and the potential for clinical translation,this review also identifies challenges associated with the implantation and integration of neural electrodes and presents recent advances in solutions,aiming to reshape electric treatments for neurological diseases.