GoKawiilIntegrative 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.
Fig. 2: Structure and oxygen delivery mechanism of diving-suit system. Full size image A Diving suit integrates i) an oxygen generator, ii) a flexible waterproof shell and iii) oxygen delivery tubes. The generated oxygen is delivered through tubes to the thoracic spiracles via spiracle connectors, forming a sealed respiratory pathway. B Oxygen generator design. i) Exploded view of oxygen generator. It includes: a container with a MnO 2 -deposited cellulose sponge inside, a sealing lid, and a hydrophobic PTFE microporous membrane. ii) Working principle of hydrophobic PTFE microporous membrane, which allows gas to pass through while preventing liquid penetration. C Optical microscope image of thoracic spiracles. The left one is the prothoracic spiracle, which remains open with a lip-like structure. The right one is the mesothoracic spiracle, which stays closed with only a small hole open. D Customised spiracle connectors with oxygen delivery tubes. E Installation of the oxygen delivery tube with spiracle connector to i–ii) prothoracic spiracle, iii–iv) mesothoracic spiracle.
Oxygen was generated through the MnO 2 -catalysed decomposition of H 2 O 2 , which produces only water and oxygen as by-products and proceeds readily under neutral conditions15,16,17. When MnO 2 powder was directly mixed with H 2 O 2 solution in the confined 1.6 ml reactor caused rapid decomposition, vigorous bubbling and fluid agitation15,18, which destabilised the cockroach’s movement. Hence, MnO 2 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, H 2 O 2 was dripped onto the sponge, which serves as a carrier for the H 2 O 2 solution and a substrate for MnO 2 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 MnO 2 -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 H 2 O 2 solution, MnO 2 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 H 2 O 2 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 H 2 O 2 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 MnO 2 catalytic sites on the cellulose sponge and the utilisation of small reactant amounts (2 mg MnO 2 powder and 3% H 2 O 2 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 H 2 O 2 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 impact21,22. 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 H 2 O 2 –MnO 2 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 cockroaches23,43, locusts24,25, and beetles26,27. These insects share similar body structures and tracheal respiratory systems28,29,30,31,32,33,34 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.
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