Mechanical metamaterials store information in the switching of bistable elements, but until now readout has relied on visual inspection or quasi-static measurements. Nearby in the archive are works on mechanical memory, wave control, and smart materials, but they either focus on writing or use local actuation. This work fills the gap: it shows that both writing and reading can be done with boundary dynamic pulses alone, without direct access to each cell.
A one-dimensional chain of N mass-in-mass cells was built. The outer mass of 33.6 g is connected to the inner mass of 3.8 g via a bistable von Mises truss; neighboring outer masses are connected by linear springs with stiffness 1020 N/m. For the stiffness asymmetry, a permanent magnet is attached to one side of the outer mass, contacting the inner mass only in state 1. This shifts the resonance frequency of the inner mass from 26 Hz (state 0) to 280 Hz (state 1). Writing was performed with a single bipolar pulse from a low-frequency shaker, reading with a weak Ricker pulse with a center frequency of 30 Hz and amplitude of 1.8 mm, and the response was recorded with an accelerometer on the outer mass of the last cell.
For the three-cell chain, all eight configurations were distinguished by the time evolution of the outer mass acceleration under a weak probing pulse. The maximum normalized cross-correlation coefficient between two independent datasets for identical configurations was close to unity, confirming readout reliability. The method remained valid when varying inner masses (6.5 g, 3.8 g, 8.5 g) and energy barriers (0.19 mJ, 1.37 mJ, 0.67 mJ). In the eight-cell chain with a gradient of barrier heights (from 8.3 mm to 12.1 mm along the strut length), the final configuration depended monotonically on the input pulse amplitude: at 2.4 mm no cell switched, at 2.9 mm one switched, at 4.1 mm two switched, and so on. This allowed the structure to be used as a discrete amplitude sensor with a resolution of about 3 μm in amplitude. Furthermore, at frequencies of 35 Hz, 38.5 Hz, and 47.5 Hz, the kinetic energy of the last cell changed by factors when states switched: increases of 180% and 695% at 35 Hz, decreases of 29% and 42% at 38.5 Hz, and nonmonotonic changes of 66% and 55% at 47.5 Hz.
This work differs from neighboring studies in that it combines dynamic writing and dynamic reading in a single architecture and tests it experimentally on chains with nonidentical cells. It is not just another way to store bits, but a demonstration that a mechanical system can simultaneously be a memory, a sensor, and a tunable wave filter. This approach paves the way for fully mechanical computing devices without electronics.
The principle easily scales to more cells for increased memory capacity and to two- or three-dimensional lattices for controlling wave direction. Optimizing cell geometry could improve switching speed and reliability. It is also interesting to investigate multiple write-read cycles and the effect of material fatigue on the long-term stability of states.
The results will influence the development of soft robots, adaptive acoustic devices, and mechanical computers, where electronics are undesirable or operation in extreme conditions is required.
Immediate next steps include testing chains with dozens of cells, exploring two-dimensional arrays for spatial encoding, and developing protocols for noise-robust readout in the presence of external vibrations.
For mechanical metamaterials, the long-term stability of bistable states under cyclic loading and the minimum energy required for reliable switching remain open questions. This work does not solve these problems, but it provides an experimental platform for their systematic study.
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The study builds a one-dimensional chain of bistable 'mass-in-mass' cells with stiffness asymmetry introduced by a permanent magnet. Configurations are written by a single bipolar pulse and read out with a weak Ricker pulse, while the response is recorded by an accelerometer on the last cell. Experiments on chains of three and eight cells show that all configurations are distinguishable and demonstrate operation as both an amplitude sensor and a tunable wave filter.
Where its strength is
Combining dynamic writing and dynamic readout in a single architecture, with experimental validation on non-identical cells. This allows the system to serve simultaneously as memory, sensor, and wave filter, paving the way for fully mechanical computing devices.
Where it could go next
Worth trying
Why this may matter
If dynamic readout scales to larger systems, it could lead to fully mechanical information storage and processing devices that operate without electronics and are robust to extreme conditions.
Nearby works in our archive
The archive is sparse around this work: the closest review is only 0.58, against a usual 0.64. It looks like few have drilled nearby.
The difference in resonance frequencies between states 0 and 1 is 254 Hz, comparable to the difference between the low note of a double bass and the high note of a violin.
The idea of mechanical memory without electronics echoes the computers from Frank Herbert's "Dune," where the ban on thinking machines forced people to create alternative information-processing technologies.