The pixel mechanical metamaterial (PMM) was developed by the array of uncoupled constrained mechanical pixel (MP), which exhibited a great degree of design freedom, modularity and diversity of mechanical properties. Inspired by the microstructural configuration of collagen fibers of biological tissues, helical ligaments were introduced into the 3D chiral structure and combined with 4D printing to develop tension-torsion coupled MP and PMM with adjustable and reconfigurable mechanical properties. The deformation mechanism of the MP from bending-dominated deformation mode to the stretching-dominated deformation mode was revealed, and the reconfigurable properties of the nonlinear mechanical behavior of the MP were verified. The ligament configuration and node spacing of MPs created an opportunity for the fabrication of buffer devices. During impact, the node spacing allowed the ligament to deform in a large space, thus providing sufficient buffer for the fragile objects. Due to the shape memory characteristics, the node spacing and configuration of MPs in the buffer device can be adjusted to achieve different buffer effects. For example, the egg fell from a height of 500 mm on the programmed buffer device and broke immediately, while the egg remained intact when it fell from 1000 mm to the unprogrammed buffer device.
