## 1 Introduction
The experiment and simulation results indicate that the harvester with four/six piezoelectric stacks could generate an average output power density of 3.4 \(\upmu\)W/mm\({}^{3}\) and 3.9 \(\upmu\)W/mm\({}^{3}\) at a speed of 5.6 km/h and 9.7 km/h, respectively. [PERSON] et al. [56] proposed a sandwiched piezoelectric transducer (SPT) with force amplification end-caps to harvest energy from large impacts. The experiments and simulation reveal that the prototype of SPT can output an average power of 4.68 mW at a 1-KN 2-Hz sinusoidal exaltation and 2.5 mW at a footstep excitation of a 4.8 km/h walking speed for a person of 70 kg. [PERSON] and [PERSON] [57] studied a slipper harvester to absorb human walking energy by using the bending of the slipper instead of the heel strike and foot pressure as an energy source. Although the preceding footstep harvesters generate a notable output power in the practical utilization, they still have some weaknesses to limit the improvement of their energy harvesting efficiency. For beam-style footstep harvesters, they usually cannot make the piezoelectric ceramic patches bonded on their substrate surfaces have a uniform surface strain in the working process and the substrate consumes most of the strain energy, which leads to a low energy harvesting efficiency of the harvesters. For stack-style footstep harvesters, they usually cannot make the piezoelectric stacks have a distinct strain in the working process for the huge Young's modulus of the piezoelectric ceramics and the weak treading excitation, which causes the piezoelectric stacks (d\({}_{33}\) mode) of footstep harvesters to have a small output power density in the working process. In view of this, novel U-shaped/L-shaped beams were proposed, which have a high energy harvesting efficiency because their uniform and notable strain in flexible piezoelectric coupled segments (PCSs) even in a small excitation [58; 59; 60; 61]. It is noted that the tested output power and power density from the L-shaped piezoelectric coupled beam (LPCB) in the author's previous work [59] cannot reach up to an ideal values because of the small yield strength of the Acrylonitrile Butadiene Styrene (ABS) substrate in the experimental specimen. Actually, if the ABS substrate is replaced by those with bigger yield strength such as aluminum alloy substrate, the output power and power density of the L-shaped harvester should be improved greatly. Therefore, in this research, two pairs of distinctive L-shaped piezoelectric coupled beams (LPCBs) and their matching piezoelectric bricks made of aluminum alloy are correspondingly designed and customized. Each specimen includes a pair of LPCBs, a force amplifier based on force amplification mechanism [62; 63], and a case. The novel piezoelectric bricks are ingenious for two reasons: first, the force amplifier can amplify the force from footstep; second, the utilization rate of the piezoelectric patch is improved for the uniform and notable surface strain in PCSs of the LPCB. In order to verify the effectiveness of the harvester, experiments of two piezoelectric brick specimens were conducted, and the effects of treading excitation, force arm length of LPCBs, PCS number of an LPCB, and unimorph/bimorph PCS on the electric output parameters of the harvester were studied. Some valuable conclusions are obtained to instruct the practical design and utilization of the novel piezoelectric bricks.