Since their advent in 2012, TENGs have set a new benchmark in energy harvesting and active sensing, establishing their presence in a myriad of domains including green energy, molecular detection, healthcare, and gesture recognition ^{[1][2][3][4][5][6]}[1,2,3,4,5,6]. Their dual functionality as energy harvesters and intelligent sensors positions TENGs as a promising solution for environmentally friendly and personalized healthcare. The array design in TENGs has emerged as a pivotal aspect in crafting TENG-based biosensors that expand their feasibility in health monitoring, environmental sensing, and point-of-care diagnostics by enhancing their sensitivity, adaptability, and spatial resolution ^{[7][8][9][10][11][12][13]}[7,8,9,10,11,12,13].

However, despite the remarkable advancements in this field, challenges persist concerning power output, device stability, biocompatibility, and integration with other cutting-edge technologies such as flexible electronics and advanced data processing systems ^{[14][15][16][17][18][19][20][21]}[14,15,16,17,18,19,20,21]. In recent years, research directions have been focused on addressing these limitations and exploring new pathways for amplifying the performance and capabilities of these adaptable devices, and AD-TENGs are distinctively recognized because their matrix configuration nurtures a diverse approach towards detection and energy harvesting ^{[22][23][24][25]}[22,23,24,25]. This grid-like framework inherently houses essential qualities such as enhanced sensitivity, superior spatial resolution, redundancy, and the ability for concurrent multi-detection, elements vital for dynamic monitoring functionalities ^{[26][27][28][29]}[26,27,28,29]. Moreover, AD-TENGs are adept at registering subtle physiological alterations, thereby holding immense potential to steer the course of advancements in healthcare and wearable technology ^{[30][31][32][33][34][35][36]}[30,31,32,33,34,35,36]. The overarching goal of the current research is to hone and maximize these attributes, promoting the evolution of robust, efficient, and precise data collection systems.

Compared to piezoelectric, electromagnetic, and thermoelectric, array-designed triboelectric nanogenerators (AD-TENGs) stand out due to several key advantages ^{[37][38][39][40][41][42][43]}[37,38,39,40,41,42,43]. First, they exhibit high efficiency and energy output, particularly because their array design enhances power generation efficiency. Secondly, their modularity and scalability make them versatile for applications ranging from small-scale wearables to larger energy systems. AD-TENGs are also notable for their flexibility and adaptability, conforming easily to different shapes and surfaces, which is crucial for wearable healthcare devices [44]. The array configuration enhances both sensitivity and spatial resolution, allowing for the detection of subtle physiological changes, essential in healthcare diagnostics. Additionally, AD-TENGs offer redundancy and multi-detection capabilities, ensuring reliable performance even if individual units fail. In terms of fabrication, they are generally more cost-effective and simpler to produce than other nanogenerators, using low-cost materials and straightforward processes. Environmentally, AD-TENGs are favorable due to their reliance on non-toxic materials, making them more sustainable. Lastly, their versatility in energy harvesting from various mechanical movements, including human motion and natural elements like wind and water, makes them highly adaptable for diverse applications ^{[45][46][47][48]}[45,46,47,48]. These attributes collectively position AD-TENGs as highly effective and versatile for a range of applications, particularly in healthcare diagnostics and wearable technology.

2. Array Configuration Amplifies TENG Energy Collection

2.1. The Principle TENG

TENGs, similar to TENGS with other various designs, capitalize on the triboelectric effect coupled with electrostatic induction to transform biomechanical energy into usable electrical energy ^{[49][50][51][52]}[68,69,70,71]. This conversion process initiates when materials possessing distinct electronegativities come into contact, facilitating the transfer of electrons between them. Subsequently, as these materials part ways, an electrostatic induction initiates, steering the flow of electrons towards the external load and thereby engendering an alternating current that sustains through repeated cycles of contact and separation. In principle, TENGs predominantly exhibit four core modes of operation, which are delineated below and illustrated in Figure 12a. Vertical Contact–Separation Mode: Within this modality, two triboelectric materials carrying opposing electrical charges are stationed in close proximity, undergoing periodic cycles of contact and separation along a vertical trajectory. This contact fosters the generation of triboelectric charges at the mutual interface. As the materials disengage, a redistribution of these charges occurs, fostering an electrical potential difference that instigates the flow of electrons through an external load, thereby generating electric power ^[54][55][73,74]. Lateral Sliding Mode: This mode witnesses two triboelectric materials, holding opposite charges, engaging in a horizontal sliding motion against each other. This relative movement, parallel to their interface, leads to a dynamic alteration in the overlapping area, thereby creating an electric potential gradient. This gradient acts as a catalyst for the flow of electrons through an external circuit, thereby generating electricity ^[56][57][75,76]. Single-Electrode Mode: In this scenario, one of the materials boasts an attached electrode, whereas the counterpart remains electrically isolated. This isolated component undergoes periodic cycles of contact and separation with the material having the attached electrode. This interaction engenders triboelectric charges at the interface, inducing a flow of electrons through the connected ground electrode and the singular electrode, thereby producing electrical power ^[58][59][77,78]. Freestanding Triboelectric Layer Mode: Here, a standalone triboelectric layer, flanked by electrodes on either side, exhibits opposing triboelectric charges on its two facets. This layer undergoes a sequence of contact and separation with the electrodes, inducing a deformation in the layer. This mechanical action facilitates the generation of triboelectric charges at the interfaces between the freestanding layer and the electrodes. The induced electric potential difference propels the flow of electrons through an external circuit, culminating in the generation of electrical energy ^[60][61][79,80].

2.2. Design and Optimization of Array-Designed TENG

In an AD-TENG system, the integration of multiple TENG units into a singular array leads to a significant increase in total energy output (Figure 2b). Each unit contributes individually to the energy harvesting process, resulting in a cumulative effect that substantially elevates the overall power generation. This synergistic operation is a cornerstone in the design philosophy of AD-TENGs, providing a robust framework for efficient energy conversion. Moreover, the array configuration ensures a uniform distribution of mechanical stress across the TENG units. This uniformity is crucial for the consistent activation of all units, thereby optimizing the energy harvesting efficiency. It also plays a key role in enhancing the durability and reliability of the system. The redundancy afforded by multiple units ensures that the failure of any single unit does not critically impair the overall performance, thereby extending the operational lifespan of the AD-TENG. Flexibility in design is another hallmark of AD-TENGs. The array can be tailored in various shapes and sizes, making it highly adaptable to specific requirements, especially in applications like wearable technology and biomedical devices. This customizable nature of AD-TENGs opens avenues for their incorporation into a multitude of platforms, ranging from small-scale electronic devices to larger energy harvesting systems. The scalability of AD-TENG arrays is an essential feature, allowing for adjustments in size and configuration to meet the desired power output for different applications. This scalability, coupled with the ease of integration with electronic circuitry, facilitates sophisticated control and optimization of harvested energy, which is particularly beneficial in applications requiring precise energy management, such as smart sensors and IoT devices. Furthermore, the array design presents numerous opportunities for optimization in material selection, structural design, and operational modes. Tailoring each unit within the array to specific operational conditions can significantly enhance the overall performance of the AD-TENG. Additionally, in applications requiring high spatial resolution, such as sensing and health monitoring, the array design allows each unit to act as an independent sensor, providing detailed information about mechanical interactions or physiological parameters.

2.3. Improving Energy Collection Efficiency

In the realm of energy harvesting, the optimization of array structures to amplify both energy collection efficiency and stability stands as a focal point of innovation ^{[62][63][64][65]}[58,81,82,83]. A notable breakthrough in this area is epitomized in Han et al.’s research, which unveils a remarkable stride in harmonizing efficiency and enduring performance through sophisticated array configurations ^[66][49]. In this study, a hybrid TENG was conceptualized and realized to exploit the intricate dynamics of ultra-low-frequency wave energy—a sector traditionally marked by its intricate patterns and directional unpredictability. The three strategically aligned TENGs significantly amplify both space utilization and volume power density, while ensuring a continuous and stable energy collection ability compared to other devices. This accomplishment, evidenced by peak volume power densities of 2.02 and 16.96 W m⁻³ for F-TENG and H-EMG, respectively, at a 1.4 Hz stimulation frequency, delineates a significant advancement in the creation of self-powered intelligent marine monitoring systems and a spectrum of energy harvesting applications within smart city frameworks. Building upon recent strides in energy harvesting, Zhang et al.’s research marks a significant leap forward. This team has ingeniously crafted a hybrid structure combining three-dimensional polypyrrole nanoarrays with porous poly (vinylidene fluoride) films, a design that significantly bolsters the mechanical robustness and electrical yield of TENGs ^[67][52]. The core innovation of this approach resides in its strategic manipulation of frictional interaction, a pivotal factor in energy generation. By augmenting the contact surface area and enhancing the affinity for contact, these nanoarrays substantially elevate the TENG’s efficacy. This amplification in performance positions the device as a potent and reliable energy harvesting mechanism, particularly suitable for use in personal electronic devices. Moreover, Saqib et al. introduces a revolutionary approach to enhancing energy harvesting efficiencies ^[68][53]. In this new configuration, each individual particle, which originally functioned as a standalone unit in P-TENG, becomes an integral element of a larger array. This array, composed of multiple such particles, each housed in rapidly degradable gelatin capsules and utilizing cellulose-based materials, significantly amplifies the system’s power generation capacity. As each particle contributes to the collective energy output, the overall system can now generate voltages and power at scales much higher than the original P-TENG’s range of 15 to 85 volts and 5.488 to 70 microWatts. The array formation ensures efficient energy harvesting from all directions, thereby eliminating the limitations of traditional contact and separation methods. This modular and scalable approach not only makes the TENG highly adaptable to various applications, particularly those involving small and irregular movements, but also maintains the eco-friendly ethos of the original design by using biodegradable components. Consequently, the TENG emerges as a highly efficient, versatile, and sustainable solution in the realm of energy harvesting technologies.