Integrative design of diving suit for underwater survival and mobility

A chemical reactor-based oxygen generation unit (Fig. 2A, i), was implemented to eliminate the need for electronic components and maintain a compact, insect-mountable design. This oxygen generator unit is housed within a lightweight and flexible shell that attaches easily to the insect’s body (Fig. 2A, ii). Given that cockroaches breathe via thoracic spiracles¹⁴, oxygen delivery tubes were installed to connect the generated oxygen to the thoracic spiracles (Fig. 2A, iii). The tube tips were shaped for secure mechanical attachment to the spiracular valves, forming an integrated and wearable diving suit.

Oxygen was generated through the MnO₂-catalysed decomposition of H₂O₂, which produces only water and oxygen as by-products and proceeds readily under neutral conditions^15,16,17. When MnO₂ powder was directly mixed with H₂O₂ solution in the confined 1.6 ml reactor caused rapid decomposition, vigorous bubbling and fluid agitation^15,18, which destabilised the cockroach’s movement. Hence, MnO₂ was deposited onto a highly absorbent hydrophilic cellulose sponge (1 × 1 cm). This configuration confined the reaction to solid–liquid interfaces, where oxygen was generated from numerous separated microsites (Supplementary Fig. S1), preventing gas accumulation and large-bubble coalescence. To prevent liquid agitation and ensure stable oxygen release, H₂O₂ was dripped onto the sponge, which serves as a carrier for the H₂O₂ solution and a substrate for MnO₂ deposition. To ensure the safe operation of oxygen generators near insects, the generator structure must prevent chemical leakage and transport only oxygen to the outside shell. The oxygen generator comprises the small container that housed MnO₂-deposited sponge and a lid that incorporated hydrophobic PTFE microporous membrane with a pore size of 0.22 µm (Fig. 2B, i). The micropores allow gas to permeate but block liquid penetration. The membrane was integrated into the lid, allowing the gaseous oxygen alone pass through and be released outside while remaining H₂O₂ solution, MnO₂ powder (mostly 1–10 µm in diameter, larger than the pore size), and the generated liquid water were retained inside the generator, eliminating risk of chemical leakage (Fig. 2B, ii). Sealing stability of the oxygen generator was confirmed by subjecting the assembled unit to agitation on a vortex shaker for 10 min to simulate mechanical shocks. Afterward, the lid surface was wiped with water-sensitive test paper, and no colour change was observed. That unit was then placed with the lid and membrane facing downward over another piece of water-sensitive test paper for 3 h. No colour change was detected on the paper, confirming that no liquid leakage occurred. To further evaluate potential biological impact on long-term exposure to byproducts of H₂O₂ decomposition, five diving suit-wearing cyborg insects were monitored for three days following experimental exposure. All individuals survived throughout the observation period with normal behaviours. Because the decomposition of H₂O₂ is exothermic¹⁹, excessive heat could disturb the insect’s physiology. However, no noticeable temperature rise was detected at the oxygen generator when monitored with an infrared camera (Ti400, Fluke), with the temperature remaining between 23.6 and 24.0 °C throughout the reaction (Supplementary Fig. S2). This result suggested that the dispersed MnO₂ catalytic sites on the cellulose sponge and the utilisation of small reactant amounts (2 mg MnO₂ powder and 3% H₂O₂ solution) minimised the heat release, prevented localised heat accumulation and allowed the generated heat to diffuse without affecting the surrounding temperature. Future improvements in oxygen generators could focus on actively regulating oxygen generation rates. For example, integrating miniature oxygen concentration sensors and micropumps would enable quantitative delivery of H₂O₂ based on real-time oxygen levels within the suit, thereby achieving dynamic oxygen supply matched to the insect’s activity states and overcoming limitations of the current passive system.

Initially, dorsal mounting of the oxygen generator on the cockroach created significant water-resistance during underwater locomotion and raised the centre of gravity to approximately 1.7 cm, causing postural instability and rollover. The ventral side provided only a limited gap of 2–3 mm from the ground, insufficient to accommodate the oxygen generator there. To preserve the insect’s streamlined body profile and maintain a low centre of gravity, the generator was therefore positioned at the posterior end of the abdomen and secured by enclosing both the generator and the abdomen within the lightweight and flexible shell (Fig. 2A, i). This configuration enabled stable and smooth underwater walking without rollover.

The shell was designed as a thin-walled (1 mm), flexible enclosure that wraps around the cockroach’s abdomen, enabling fabrication with flexible resin, preserving natural movement, and accommodating individuals with slight size variations (Fig. 2A, ii). The shell geometry was modelled on the natural morphology of the cockroach’s abdomen, incorporating an oval cone shell led to the least impact on the cockroach’s movement²⁰ and maintained the streamlined body form of the cockroach. The cone’s wide opening allowed the shell to slide smoothly over the tapered abdomen from the posterior end, making the installation straightforward. The anterior end of the shell was sealed to the cockroach’s first abdominal segment with a soft nitrile rubber membrane (0.16 mm thick, 1.0 cm wide). The membrane filled the narrow gap between the shell and the exoskeleton surface, forming an elastic seal that prevented water ingress and maintained a watertight interface. Its flexibility allowed the membrane both to accommodate slight variations in abdominal size among individuals and to deform with the cockroach’s body during locomotion (Supplementary Fig. S3), thereby preserving natural vertical and lateral movement.

The oxygen delivery tubes transport oxygen from the oxygen generator inside the shell to the thoracic spiracles (Fig. 2A, iii). One end of the tubes connects to the shell; the other end connects to the spiracles. The external, soft and anatomically distinct nature of the two pairs of thoracic spiracles (Fig. 2C) presents a design challenge¹⁴. The prothoracic spiracles remain open, forming a groove that directly exposes the spiracular valve, whereas the mesothoracic spiracles remain closed, leaving only a small hole visible. This complexity mandated the design of customised connectors to achieve a tight seal that ensures both effective oxygen delivery and waterproof sealing. The prothoracic spiracles connector has a spoon-shaped cover with an oval cap (Fig. 2D, i), designed to fully enclose the spiracular valve exposed at the prothoracic spiracle (Fig. 2E, i, ii). Conversely, the mesothoracic spiracles connector has a thin tube (ID = 0.3 mm, OD = 0.4 mm) (Fig. 2D, ii), which can be inserted into the small hole (Fig. 2E, iii, iv). Upon attachment to the spiracles, these spiracular connectors prevent water from entering the respiratory system, ensuring stable oxygen transport.

The diving suit’s waterproof performance was validated through immersion and mechanical bending tests (See Method 3.5). Waterproof integrity was confirmed after 30 min of immersion and repeated joint bending, the water-sensitive paper placed inside the suit showed only a small colour change (Supplementary Fig. S4), without the typical blue coloration that indicates water penetration. A control test performed in air produced a small color change (Supplementary Fig. S4), confirming that the observed change originated from the insect’s respiratory moisture rather than from external leakage. These results substantiate the suit’s ability to maintain a waterproof barrier under long-term immersion and mechanical deformation. Multi-directional drop tests were conducted to assess tolerance to accidental mechanical impact^21,22. The cyborg insects with diving suits were released from heights ranging from 20 cm to 1 m in various postures, simulating real-world fall and collision scenarios. Throughout all tests, the diving suit structure remained intact without damage, the oxygen generator operated without leakage, and the cockroach remained active and capable of responding to external stimuli, demonstrating adaptability to mechanical impact. Furthermore, the suit’s performance under different water levels was evaluated by immersing the cyborg insects with a diving suit to depths ranging from 5 to 50 cm (approximately 20 times the body length). The diving suit maintained structural integrity at all test depths without deformation, and the internal test paper exhibited no blue colour change, confirming that no leakage occurred under increased water pressure. Meanwhile, the cockroach remained alive and exhibited normal locomotion across all depths.

Overall, the integration of the miniature H₂O₂–MnO₂ based oxygen generator, flexible shell, and specially designed oxygen delivery tubes facilitates stable underwater respiration and locomotion while preserving natural behaviour. These outcomes confirm that the diving suit enables the cyborg insects to maintain respiration, waterproofing, and mechanical resilience underwater.

Moreover, the proposed diving suit concept could be potentially extended to other terrestrial cyborg insect platforms, such as cockroaches^23,43, locusts^24,25, and beetles^26,27. These insects share similar body structures and tracheal respiratory systems^{28,29,30,31,32,33,34} in which oxygen enters through paired spiracles and is distributed through internal tracheal networks³⁵. These similarities suggest that the strategy of combining an abdominal protective shell with oxygen delivery to the spiracles may also be applicable to terrestrial insect species. However, species-specific differences in morphology, locomotive behaviour, and payload capacity may introduce engineering challenges. For example, jumping insects such as locusts may require optimisation of suit weight and hydrodynamic design, while insects with wings folded along the abdomen may require modified shell geometries to avoid interference with wing deployment. In addition, species with limited payload capacity may necessitate further miniaturisation of the oxygen generation system and the use of ultralight materials. Therefore, adapting the diving suit to different insect species will likely require species-specific optimisation of structural design and device miniaturisation. Such adaptations could further broaden the applicability of the diving suit to diverse terrestrial insects, enabling a wider range of amphibious cyborg insect platforms.

In-suit oxygen concentration monitoring and metabolic rate

To assess the impact of the miniaturised oxygen generator on cockroach respiration and locomotor abilities, the oxygen generation rate, oxygen consumption rate, and in-suit oxygen concentration were measured. The introduction of 1.0 ml of 3% H₂O₂ to the oxygen generator yielded a cumulative oxygen production of 6.2 ± 0.2 ml (Fig. 3A). To evaluate the capability of the diving suit and oxygen generator, the oxygen level in the suit was measured while the cyborg cockroach walked on a treadmill (Fig. 3B). The oxygen level inside the suits increased and reached the peak at 8.0 min after injection of 1.0 ml H₂O₂ (47.4 ± 14.2%, mean ± standard deviation, N = 6) (Fig. 3C, blue line). Thereafter, the oxygen level gradually decreased, reaching 14.8 ± 3.4% after 3 hours. Such an oxygen concentration is sufficient for insects to sustain normal physiological function³⁶.

In the control test without H₂O₂ introduction, respiratory oxygen consumption caused the oxygen level inside the suit to continuously deplete, dropping to 6.2 ± 2.7% (mean ± standard deviation, N = 4) in 1 h (Fig. 3C, red line). Given that oxygen levels below 5% suppress insects activity and can lead to mortality^37,38, operation of cyborg cockroaches without the generator is limited to less than 1 h. Reaction to electrical stimulation revealed the enhanced locomotor activity under maintained oxygen levels (Fig. 3D). During the first 5 min (i.e., first ten stimulations), cockroach with oxygen supply showed the highest response with the induced speed of 5.9 ± 3.5 cm/s. Despite the expected decline in speed due to habituation, induced forward movement was sustained above 1.4 cm/s even after 2 h (Fig. 3D, blue line). The induced speed in the group without oxygen supply fell below 0.5 cm/s after 30 min, indicating that the cockroach was deemed to stop responding³⁹. The total walking duration was 28.8 ± 7.6 min with oxygen supply and 11.9 ± 7.4 min without it. These results confirmed that oxygen supply in the suits maintained prolonged locomotor activity of cyborg cockroaches. The oxygen requirement of the cyborg cockroach was also determined (See Method 3.7). At rest, they consumed 2.3 ± 0.4 ml/h (mean ± standard error, n = 12, N = 3), rising to 3.8 ± 0.6 ml/h (mean ± standard error, n = 12, N = 3) while walking. Considering oxygen production rate (Fig. 3A), the estimated survival time exceeds 1 h for continuous walking and 2–3 h while resting, even without an external oxygen supply.

Survivability and locomotion test

The operational capability of the cyborg insects in submerged environments was evaluated following confirmation of the diving suit design and feasibility. Cyborg insects with diving suit sustained activity and responsiveness to external electrical stimuli for 2–3 h underwater (Supplementary Movie S1). In contrast, a control cockroach without the diving suit suffocated within 2 min (Supplementary Movie S1). These findings establish that the diving suit, by sealing out water and supplying oxygen, extended the cockroach’s underwater survival time from a few minutes to several hours. Furthermore, cyborg insects wearing a diving suit exhibited user-induced entry and exit from water, demonstrating prolonged controllability and maintained physiological activity across the land–water interface (Supplementary Movie S2).

Locomotion of the cyborg insects was then evaluated on land and underwater. On land, the suit-wearing cyborg insects achieved an average forward speed of 87.5 mm/s, with left-turn angular speed of 58.6°/s and right-turn angular speed of 58.1°/s (Fig. 4B, i–iii). Underwater, the average forward speed was reduced to 78.4 mm/s, and average left-turn and right-turn angular speed declined to 35.2°/s and 28.2°/s (Fig. 4D, i). The reduction in both forward and turning speeds underwater (a 10.4% decrease for forward speed and 39.9% and 51.4% declines for left- and right-turn speeds, respectively) is primarily attributable to increased hydrodynamic resistance. This disparity, where angular speed loss is more pronounced than forward speed loss, stems from geometric and hydrodynamic factors. The elongated, elliptical body of the suit-wearing cockroach increases the frontal area exposed during turning, thereby enhancing fluid resistance^40,41. In addition, vortex shedding and unsteady flows around the body generate extra vortex-induced drag^40,42, resulting in greater speed loss during turning underwater.

Long-term underwater performance was assessed by monitoring locomotion activity underwater for 3 h (Fig. 4D, i–v). A gradual reduction in both forwards and angular speeds was observed, primarily attributed to physiological fatigue and stimulus habituation^39,43,44. The forward speed diminished from 78.4 mm/s at 5 min to 52.3 mm/s after 3 h. The right-turning angular speed decreased from 27.5°/s to 10.7°/s, while the left-turning angular speed dropped from 34.6°/s to 14.1°/s. A previous study demonstrated that cyborg cockroaches achieved point-to-point terrestrial navigation at average forward and angular speeds of 29.0 mm/s and 6.95°/s³⁹. In comparison, the suit-wearing cyborg insects maintained higher locomotion speeds underwater, indicating that the diving suit also enables path control in aquatic conditions.

Analysis of average speeds before, during, and after stimulation revealed further differences in aquatic locomotion (Fig. 4E). Unlike the rapid speed decay observed in air post-simulation, the underwater average post-stimulus speed (Fig. 4E, blue line), particularly during manoeuvres, occasionally surpassed the average speed during stimulation (Fig. 4E, red line). These delayed acceleration and deceleration responses result from the added-mass effect of surrounding water^45,46. When cockroaches accelerate from rest, the surrounding fluid exerts an opposing added mass force that resists their motion. Conversely, during deceleration, an added mass force continues to exert a forward thrust, thereby prolonging the slowing-down process. Concurrently, the experiments revealed that cockroaches’ tarsal claws remained anchored to the substrate underwater, contrasting with relaxed leg positions in air. This sustained gripping behavior counteracted upward buoyancy and rotational instability caused by hydrodynamic disturbances. Consequently, cockroaches should continuously exert vigorous claw grips to maintain equilibrium. This sustained gripping behaviour may also contribute to the slower motor responses observed underwater.

The amphibious moving speed of suit-wearing cyborg insects was compared with that of reported amphibious robots by normalising speed to body length per second (BL/s)^{47,48,49,50,51,52,53,54,55,56,57,58,59,60,61}. On land, amphibious cyborg insects achieved 1.1 BL/s, surpassing most amphibious robots (typically below 1.0 BL/s) (Fig. 4C, i). Underwater condition, our system achieved a speed of 1.0 BL/s, again outperforming most existing designs (typically below 0.8 BL/s) (Fig. 4C, ii). When compared to other centimetre-scale amphibious robots with reported angular speeds^60,62,63, the cyborg cockroach with the diving suit exhibited a several-fold higher angular speed on both land and underwater.

Overall, the diving suit enables cyborg insects to operate in both terrestrial and aquatic environments, extending their operational scope to amphibious conditions while preserving locomotion capability.

Demonstrations of survival, adaptation

Operational validation required testing the diving suit’s capability to traverse simulated hazardous environments and underwater narrow crevices. To examine whether the diving suit allowed cyborg cockroaches to operate under combined hazardous conditions, they were tested in a 1.7-m-long tunnel (5 × 5 cm cross-section) composed of a CO₂-filled section followed by a water-filled section (Fig. 5A), representing typical environmental threats—anaesthetising gases^64,65,66 and full submersion. The cyborg insect without the suit exhibited disoriented movement, erratic leg movements, and loss of responsiveness to external stimuli within seconds after CO₂ exposure (Fig. 5B, Supplementary Movie S3). Because the cockroach became immobile in the CO₂ zone, another cyborg insect was introduced at the entrance of the water zone to evaluate its reaction to submersion. Under electrical stimulation, the cyborg insect was guided to walk into the water, where its leg movements gradually ceased, and complete immobility occurred within 45 s, suggesting asphyxia (Fig. 5C, Supplementary Movie S3). In contrast, the cyborg insect equipped with the diving suit maintained a regular gait and successfully traversed the entire tunnel (Fig. 5D, Supplementary Movie S3). Three independent trials were conducted under identical CO₂–water tunnel conditions, and all cyborg insects wearing the diving suit successfully traversed both hazardous zones (3/3 successful trials). Locomotor activity was preserved throughout both sections, demonstrating that the diving suit enables sustained respiration and movement under combined CO₂ exposure and water submersion by preventing gas and water ingress while supplying oxygen independently.

Evaluation of the cyborg insect’s capacity for manoeuvring through confined underwater spaces, necessitated testing in a narrow crevice. In submerged underwater spaces with gaps as small as 2 cm, the dorsal backpack module (Figs. 1B, 4A) protrudes from the thorax and prevents passage. The insect lacks sensory feedback to detect such obstacles and continues to push forward, eventually becoming stuck because the backpack is an external attachment. To eliminate this protrusion and enable smooth passage through confined areas, the backpack and battery were implanted inside the body, forming a fully implanted cyborg configuration (Fig. 6A)⁴⁹. Utilising this configuration, cyborg insects with the diving suit could traverse a 2-cm-high crevice (Fig. 6B, C), which would be difficult for regular cyborg insects with thorax-mounted backpack (2.5 ± 0.3 cm) and for most aquatic robots. The fully implanted configuration also altered the internal mass distribution, relocating the backpack and battery closer to the body’s central axis and thereby lowering the centre of gravity, which improved stability and reduced the likelihood of overturning during underwater locomotion. This internal configuration also prevents the snagging or detaching of external parts when navigating narrow gaps or uneven underwater terrain. Overall, these results demonstrate that the diving suit facilitates the maintenance of respiration and movement in sequential CO₂–water environments by preventing gas and water ingress, while providing an independent oxygen supply.