## 4 Design
Figure 6 illustrates one common mat design: a 2 \(\times\) 3 grid of modules, each containing multiple energy-harvesting devices (PENG, TENG, and EMG). Notable features include foldability, uniform pressure distribution, and a carefully optimized design that boosts voltage output by as much as 30% when pressure is concentrated in specific areas. Figure 5: A tile featuring 6 piezoelectric cells between wooden blocks with springs converts foot pressure into AC voltage, which is rectified and stored as DC energy for low-power applications. The mat design by [PERSON] et al. [27] consists of six modular units, each measuring 12 cm \(\times\) 12 cm \(\times\) 2.5 cm, arranged in a 2 \(\times\) 3 grid with 4.5 cm gaps between modules. This layout allows each module to operate independently, promoting flexibility and distributing foot pressure evenly. Each unit contains six piezoelectric nanogenerators (PENGs), eight triboelectric pairs (TENGs) arranged in stacks of four pairs each, and two electromagnetic generators (EMGs). A plastic stiffener helps ensure that foot pressure spreads evenly across the modules, and the entire mat is covered with PVC for durability and slip resistance. A key advantage of this design--especially relevant for high-foot-traffic environments--is that the mat can be folded, reducing its overall size for easy transport and storage. This feature makes it well-suited for locations such as religious sites, where mats often need to be folded away for cleaning and maintenance. Another important characteristic is the need for consistent and focused pressure across the modules. Testing showed that when four of the six modules were pressed at the same time, the voltage output was about 30% higher than when all six modules were engaged only intermittently [26]. In other words, regular, concentrated stepping can boost energy storage but requires continuous foot traffic to maintain stable power generation. Figure 7 illustrates how the mat has evolved through several stages of development, each offering distinct benefits. Early foot-traffic energy-harvesting mats used basic cable-based outputs to carry the harvested energy to a storage device or load. While these straightforward designs successfully converted mechanical stress into electricity, they often lacked the durability and flexibility needed for heavy-use settings. The next phase of mat design introduced stronger materials and protective layers that better withstand repeated mechanical stress, making them more reliable in high-foot-traffic areas. Further advances led to modular and foldable mats, simplifying transport, setup, and maintenance. Hybrid systems that blend PENG, TENG, and EMG technologies can capture a wider range of mechanical energy. By altering the compression mode, these designs convert footstep force into shear or bending stress--methods that can improve energy efficiency. Arranging individual transducers in series--parallel helps balance voltage and current, meeting specific power requirements. Altogether, these innovations have produced mats that are both more portable and more efficient, consistently generating electricity through everyday walking. Figure 8 presents the performance analysis of various studies focusing on materials, layout complexity, environmental suitability, power output, and stability. Each study  
Figure 7: Mat Design Evolution and Key Innovations. was rated on an ordinal scale from 1 to 5, reflecting the relative performance in each category. The scale is interpreted as follows: (a) low or minimal performance; (b) medium, meaning moderate or average performance; (c) high, indicating strong performance or high suitability. To arrive at these ratings, qualitative assessments were made:  
Materials: Assesses the quality and type of materials used for durability and efficiency. Layout Complexity: Considers how complex the design is, with higher ratings for more advanced or integrated components.