Insect-scale terrestrial robots remain constrained by limitations in agility, robustness, and onboard power, which has motivated increasing interest in terrestrial cyborg insects as a biohybrid platform that combines living insects with miniature wireless stimulation systems for locomotion control. Although prior studies have demonstrated controllable locomotion and autonomous navigation in multiple insect species, sustained operation remains hindered by the progressive attenuation of locomotory responses under repeated electrical stimulation, a limitation commonly associated with habituation and degradation of the tissue–electrode interface. "Given that insect sensory systems characteristically exhibit burst-like firing patterns, burst stimulation represents a physiologically motivated alternative to conventional continuous stimulation and a plausible strategy for improving the sustainability of locomotion control and the reliability of autonomous navigation in terrestrial cyborg insects." said the author Hai Nhan Le, a researcher at University of Queensland.
Darkling beetles (Zophobas morio) were used as the biological platform, with one common electrode implanted in the pronotum, paired working electrodes implanted in the antennae and elytra, and a miniature wireless backpack mounted on the dorsal surface to form the terrestrial cyborg beetle system. Methodologically, forward locomotion was elicited by fixed-parameter elytral stimulation, whereas antennal control was examined by comparing a conventional continuous waveform with the proposed burst stimulation protocol, which consisted of four 100-ms bursts separated by 50-ms stimulation-free intervals, while maintaining comparable voltage, pulse width, frequency range, and overall stimulation intensity across conditions. The stimulation strategy was subsequently integrated into an existing closed-loop path-following framework, in which a proportional controller adjusted antennal stimulation frequency according to orientation error, and real-time motion-capture feedback was used to guide the beetle along a predefined sinusoidal path. Locomotory and navigational performance were quantified using induced turning angle, angular velocity, linear velocity, success rate, tracking error, navigation time, and stimulation effort.
The results showed that, under conventional continuous stimulation, the antennal stimulation–induced turning response of the beetle deteriorated progressively with repeated stimuli, and this deterioration became more pronounced at higher stimulation frequencies. In contrast, burst stimulation effectively mitigated this decline. At 34–40 Hz, the decay rates of induced turning angle and peak angular velocity were reduced by approximately 30% and 88.3%, respectively, and, under the same stimulation intensity, the mean induced turning angle was increased by about 52% relative to continuous stimulation. In addition, burst stimulation preserved a stable graded frequency–response relationship across 10–40 Hz, thereby supporting its integration into closed-loop locomotion control. On this basis, the proposed navigation system achieved reliable path following, with a success rate of 73% and an average tracking error of approximately 12 mm. Further analysis indicated that a shorter control update interval improved navigation efficiency, whereas excessive consecutive unilateral stimulation was associated with response degradation and increased risk of navigation failure.
In summary, compared with traditional continuous stimulation, burst stimulation can substantially mitigate the decay of turning responses in terrestrial cyborg beetles while preserving a stable frequency–response relationship, without increasing overall stimulation intensity or power consumption. These findings indicate that a stimulation paradigm more consistent with the physiological firing characteristics of insect sensory systems may alleviate habituation and improve the reliability, accuracy, and efficiency of closed-loop locomotion control and autonomous navigation. Moreover, the observation that consecutive unilateral stimulations should be constrained provides a practical basis for subsequent controller design and stimulation optimization. "This study offers a feasible strategy for addressing the long-standing problem of sustained controllability in terrestrial cyborg insects and further strengthens the prospect of translating such biohybrid platforms from laboratory demonstrations toward operation in more realistic environments." said Hai Nhan Le.
Authors of the paper include Hai Nhan Le, Huu Duoc Nguyen, Lachlan Fitzgerald, Peter Ross McAree, Hirotaka Sato, and Tat Thang Vo-Doan.
This work was funded by a New Staff Research Start-up Fund from UQ Faculty of Engineering, Architecture and Information Technology and School of Mechanical and Mining Engineering (NS-2307) to T.T.V.-D. and the Singapore Ministry of Education (RG82/24) to H.S.
The paper, "Bust Stimulation for Sustained Locomotion Control and Autonomous Navigation of Terrestrial Cyborg Beetles" was published in the journal Cyborg and Bionic Systems on Mar 9, 2026, at https://doi.org/10.34133/cbsystems.0537.
