A critical challenge for jumping microrobots is achieving a compact actuator with a high energy output as traditional elastic actuators are inherently bulky. The integration of biological materials with artificial systems to realize biohybrid muscle actuators is a promising approach. However, previous attempts utilizing the entire organism have been hampered by the unpredictability of the native nervous system, and actuators integrating cultivated or extracted muscle tissues have so far been unable to achieve a sufficiently explosive output capacity for jumping. Here, discarded locust hindlegs are repurposed into explosive biohybrid muscle actuators that are synergistically integrated with an artificial robotic system. The resulting biohybrid locust is only 2 g in weight and is precisely controlled through electrical stimulation to achieve dynamic leaps of up to 18 times its body length and 7 times its body height, which outperforms most synthetic counterparts. The design exhibits 2 key functional advances: on the one hand, the actuator requires an ultralow-power input of only 0.03 mW via the optimization of stimulation protocols; on the other hand, the actuator rapidly releases kinetic energy, enabling the artificial robotic system to perform long-distance jumps. This paper presents an experimental validation and biomechanical analysis on the biohybrid locust to demonstrate how our strategy unlocks sustainable and high-performance actuation for microrobots. This work pioneers a roadmap for the next generation of biohybrid robots that merge ecological sustainability with engineering excellence.

Locusts are natural talent jumpers. They can easily jump over obstacles larger than their size. By integrating wireless electrical stimulation control devices, these insects can be transformed into biorobots endowed with jumping abilities. However, achieving reliable control over locust jumping has remained a challenge, with previous studies falling short of inducing stable continual jumps. In this research, we developed a locust-based biorobot based on motor neural stimulation. Neural signals were acquired and analyzed from the motor nerve N5. Then, a 400 ms artificial signal (3 V voltage, 50 Hz frequency, 3 ms pulse width) that mimics natural neural activity was applied to the N5 nerve on a body-fixed locust. Consistent leg kicking was induced by this stimulation, achieving a success rate of 90%. Subsequently, a remotely operated electronic backpack was designed and mounted onto the locust's back. Through applying electrical stimulation signals from the backpack, jumping motion can be triggered immediately with a success rate of 80%, effectively transforming the locust into a jumping biorobot. The biorobot weights 2.55 g inclusive of backpack and battery, and is capable of performing over 9 jumps continually. By incorporating cooperative antennae stimulation, the biorobot achieved precise steering control between continual jumps. This advancement allowed our biorobot to perform directional continual jumps, marking the first demonstration of targeted approximation through continual jumps.

To address the growing demand for electricity and the low efficiency of conventional onboard power generation systems of aircrafts, fuel cells have received widespread attention. In this paper, an integrated propulsion and power generation system combining the turbofan engine and the flame-assisted fuel cell (FFC) system is proposed. It’s noted that the FFC used in this system is a new type of solid oxide fuel cell (SOFC). In this study, the thermodynamic models of the turbofan engine and the FFC system are established. Based on modeling, the performance of the FFC-Turbofan system is compared with that of a conventional turbofan engine. Additionally, the parametric study is conducted, including the effects of various design parameters of the turbofan engine, flight conditions, and operating parameters of the FFC system. The results indicate that as the electric power fraction (EPF) increases from 15% to 35%, compared to the turbofan engine, the FFC-Turbofan system shows a 14.06% reduction in specific fuel consumption (SFC) and an over 16% increase in thermal efficiency and overall efficiency. Furthermore, the performance advantages of the FFC-Turbofan system are more significant. Also, under conditions of higher compressor pressure ratio and lower turbine inlet temperature, as well as higher fan pressure ratio and higher bypass ratio, the FFC-Turbofan system achieves a lower SFC and higher overall efficiency. Furthermore, the increase of fuel utilisation and equivalence ratio can reduce the SFC and increase the overall efficiency. Finally, based on the analysis of flight condition parameters, the FFC-Turbofan system is preferable for aircrafts at high altitude and low speed.

Porous transport layers (PTL) in polymer electrolyte membrane electrolysis cells ensure gas/liquid mass transport at the anode, and determine the feasibility of high current density operation up to the limiting current density (LCD). This study examined the effect of anode PTL properties on LCD by varying porosities of 45 %, 56 %, and 72 %. Electrochemical characterizations suggest that the mass transport limitation leads to an abrupt increase in the electrolysis voltage and membrane dehydration, and also indicate that the PTL with the largest porosity of 72 % achieves the largest LCD compared to the other two PTLs with smaller porosities. Moreover, visualization experiments with a high-speed microscope captured the bubble detachment sites at the interface between flow channel and PTL, and reveal that a larger PTL porosity increases the density of the detachment sites. Additionally, a correlation emerges between the bubble flow regimes at the anode channel and periodic changes of the current density. A numerical analysis incorporating the visualized bubble behavior into the boundary condition successfully predicts the dependence of the porosity on the LCD, in agreement with the experimental results. The analysis also demonstrates that a larger porosity contributes to reducing the gas saturation and enhancing the LCD.

Operation at high current density of polymer electrolyte membrane electrolysis cell (PEMEC) can reduce its electrode area and capital expense. The high current density operation is limited by the limiting current density (LCD), where electrolysis voltage abruptly increases. Effects of operating temperature and pressure on the LCD were evaluated in a lab-scale PEMEC within a range from 70 to 90 degrees C and from 0.1 to 0.3 MPa. Also, a theoretical model was developed to predict the LCD, and to clarify what determines LCD and how the operating conditions influence the LCD. The theoretical analysis suggests that when current density is close to the LCD, water mass transport at anode reaches a limitation, which indicates that water saturation reaches almost zero at anodic catalyst layer. The analysis also finds that lower operating temperature and higher operating pressure can reduce oxygen gas saturation and raise the water saturation in porous transport layer at anode, and finally enlarge the LCD.

Enhancing the durability of unmanned underwater vehicles (UUVs) would facilitate maritime research, and hydrogen fuel cells are considered a feasible solution. In this paper, based on an underwater hydrogen hybrid system mainly driven by a hydrogen-air fuel cell stack and a battery, the energy management strategy and energy storage are investigated to enhance the endurance of UUV. The results exhibit that the proposed energy management strategy integrating equivalent hydrogen consumption minimization strategy with rule-based strategy (ECMS-RB strategy), effectively reduces fuel cell power fluctuations. It is noted that, this strategy increases the state of charge (SOC) of the battery by approximately 0.2 and prevents battery over-discharge, compared to the conventional state machine strategy under identical boundary conditions. Additionally, this paper compares the performance of energy storage systems and their coupling design with UUV. The results suggest that liquid hydrogen-liquid oxygen and metal hydride energy storage systems are preferable for UVVs to achieve neutral buoyancy. Under low-speed navigation conditions, increasing the UUV length from 1.5 m to 5.5 m enhances its endurance capability by a factor of 1.78, and raising the outer diameter from 0.1 m to 0.4 m increases the endurance capability by a factor of 5.44.

Jumping is an effective way for small robots to overcome obstacles. After years of development, many miniature jumping robots have been proposed with various mechanisms, and they have achieved jump trajectory control, fall recovery, and even continuous jumps. However, most miniature jumping robots do not have enough actuators to accurately regulate the robot's jumping trajectory, which limits the robot's flexibility to traverse complicated obstacles. In this letter, a variable energy storage and release mechanism and a take-off attitude control mechanism were designed for flexible jump trajectory control. The former was inspired by the semi-lunar process of the locust's hind legs. A cross structure was designed for both steering and body uprighting. Both the static modeling of the torsion springs and the dynamic modeling of the robot jumping process were modeled. This 28 cm long, 120 g weight robot was capable of continuous jumps with precisely controlled omnidirectional trajectories. The maximum jump height and jump distance were 2 m and 4 m. This jumping robot revealed a high trajectory repeatability, with a maximum error of less than 15.5 mm. Finally, the obstacle-crossing ability of this robot with two adjustable parameters was analyzed.

Fuel cells (FC) are expected to improve the endurance of unmanned undersea vehicles (UUVs). Hydrogen-oxygen fuel cells are commonly utilized undersea, which suffer from high cost and technical problems. However, virtually all commercial fuel cells are primarily designed for open spaces, which are inappropriate for undersea applications. Based on this, this paper proposes a hydrogen-air fuel cell/battery undersea hybrid system (FCBS), and evaluates the performance of the hybrid system to address issues. The UUV studied is a small modular UUV with an external diameter of 320 mm and a cruising power of 150 W-500 W. The calculation results show that the extended length of the UUV and the reduced dive depth can improve the endurance of FCBS system. Compared with FC system, the application of FCBS system can result in a growth of 22-34% in cruise time and an increasement of 36% in maximum range. However, this advantage does not apply at high velocities. In addition, there is an optimal velocity for the UUV to reach its maximum range, which is 1.2 m/s for FCBS system and 1.5 m/s for FC system. Finally, the experiment results prove the feasibility and reliability of the proposed scheme.

Tens of crawling bio-robots with cockroaches as the mobile platform have been developed with various functions. Compared with artificial crawling robots of the same size, they revealed better flexibility, larger payload, and stronger endurance. These features made bio-robots ideal for pipeline inspection scenarios because the advancements in locomotion mechanisms and efficient power systems are still hurdles for current artificial systems. In this study, we controlled the bio-robot to crawl in the confined dark pipeline and achieved autonomous motion control with the help of an onboard sensing system. Specifically, a micro-camera was mounted on the electronic backpack of the cockroach for image collection, and an IMU sensor was used to compute its body orientation. The electronic backpack transmitted images to the host computer for junction recognition and distance estimation. Meanwhile, the insect's habituation to electrical stimulation has long been an uncertain factor in the control of bio-robots. Here, a synergistic stimulation strategy was proposed to markedly reduce the habituation and increase the number of effective turning controls to over 100 times. It is also found that both the increase of payload and the application of stimulations could promote the metabolic rate by monitoring carbon dioxide release. With the integration of synergistic stimulation and autonomous control, we demonstrated the fully autonomous pipeline navigation with our cockroach bio-robot, which realized the cycle number of approximately 10 in a roll. This research provides a novel technology that has the potential for practical applications in the future.

Jumping locomotion is critical for microrobots to overcome obstacles. Among the microjumping robots, the development of an omnidirectional jumping mechanism is challenging. To avoid the complicated microfabrication process, we present an insect-computer hybrid robot by controlling the locomotions of an Oriental Migratory Locust (Locusta migratoria manilensis, Meyen 1835). The insect-computer hybrid robot achieves repetitive omnidirectional jumps of ∼100 mm high. A series of experiments on jumping control, turning control, and collaborative directional jumping control are carried out. We also demonstrate the implementation of a wireless stimulator backpack that provides remote locomotion control, which transforms the insect into a hybrid robot. Moreover, a feedback jump control system is subsequently presented. The results indicate that the hybrid robot could easily achieve an omnidirectional jump and maintain body righting after landing. This robot is well-suited for applications that require locomotion on uneven terrains, such as environmental surveillance and search and rescue.

Jumping is a good solution for small robots over obstacles. Most of the current jumping robots are not energy store adjustable due to the design of the energy storage elements and structures, which limits the effective working space of the robot. The locust is good at jumping. Thanks to the excellent structure of the hind legs, the locust can change the degree of compression of the simi-lunar process (SLP) and change the energy storage while maintaining the same jumping stance. Herein, we design a locust-inspired energy storage joint and verified its function on a jumping robot. The motors and wires were used to imitate the muscles and the torsion springs were used to imitate SLP. To accurately describe the energy stored, a static model of the torsion springs was developed. Furthermore, the number of motor revolutions and the stored energy value were also calculated and could be used for subsequent precise control. Six jumping experiments with different compression angles for torsion springs proved the feasibility of the static model. This locust-inspired energy storage joint is the basis for the next robot capable of the omnidirectional, continuous autonomous jumping.

Insect-scale mobile robots can execute diverse arrays of tasks in confined spaces. Although most self-contained crawling robots integrate multiple actuators to ensure high flexibility, the intricate actuators restrict their miniaturization. Conversely, robots with a single actuator lack the requisite agility and precision for planar movements. Herein, a novel eccentric rotation-dependent multidirectional transmission is presented using a tilted eccentric motor and a simplistic two-legged structural configuration for planar locomotion. The speed of the eccentric motor is modulated to enable alternating microscopic jumps to propel the system, creating a mode of motion analogous to galumphing of seals. Upon modeling the motion dynamics and conducting experiments, the effectiveness of direct motion transmission is substantiated through microscopic galumphing encompassing left/right crawling and straight-forward crawling. Finally, a 1.2 g untethered robot is developed, which demonstrates enhanced straight crawling and spot turning, traverses narrow tunnels, and achieves precise movements. Therefore, the proposed motion-transmission technique provides a comprehensive set of innovative solutions of underactuated agile robots.

Many small bionic crawling robots have been invented for search and rescue missions in narrow spaces. However, their locomotion capability is far from that of insects of the same size. Transforming a cockroach into a bio-bot has been a hot topic in the past decade. Herein, we modified this insect to perform surveillance work in dark confined environments. The synergistic electrical stimulation for turning control was proposed by alternating electrical stimulation of the cerci and antennae every 5 trials. The result showed that this method was able to control cockroaches turning steadily 117 times. An electronic backpack was designed, which was capable of transmitting images in real time, and a light emitting diode (LED) was installed on the backpack providing a light source for the camera. Thus, a vision-aided navigation system was formed for dark confined environments, e.g. pipelines. With a host computer software, the operator controlled the bio-bot to pass through a completely dark and closed pipeline. The electronic backpack and the host computer were connected via transmission control protocol (TCP), which allows the operator to manipulate the bio-robot remotely. This technology can be applied in pipeline surveillance in the future.

Introduction The PEM electrolysis cell (PEMEC) exhibits great potential to produce hydrogen gas. However, the high cost associated with cell components, such as the iridium oxide catalyst and titanium porous transport layer, poses a challenge to the commercialization of PEMEC. So, continued research is needed to improve the cost-effectiveness of PEMEC. Operation at high current densities can minimize the electrode area and reduce capital expenses. However, high current density operation is limited by limiting current density (LCD), which causes a sharp increase in electrolysis voltage. At high current densities, the generation of oxygen gas bubbles creates additional flow restrictions to the water supply and increase overvoltage. Although previous studies have achieved relatively high current densities [1-2], the limit of operating current density and its mechanism still remain unknown. In this study, it reveals the impact of operating temperature and pressure on LCD of a lab-scale PEMEC. The experiments are conducted over a range of temperatures from 80 to 90 ℃ and pressures from 0.1 to 0.3 MPa. In conjunction with experiments, a mathematical model is developed to analyze the mechanism of LCD. The model includes mass and momentum equations for liquid water and oxygen gas through the porous transport layer. And the model also involves electrochemical equations to study overvoltages associated with mass transport. By combining experimental and theoretical analysis, this study provides valuable insights into the factors affecting LCD of PEMECs and facilitates the optimization of high-performance operation. Experimental apparatus The specifications of crucial components such as membrane (PEM), catalyst layer (CL), porous transport layer (PTL) is listed in Table.1 . Nafion NR212 is used as PEM, and the thickness is 51 μm. The catalyst is contained on CL, and its loading amount are 1.5 mg/cm2 IrO2 on anode and 0.5 mg/cm2 Pt on cathode, respectively. The anodic PTL is a Titanium mesh plated by Pt (Nikko Techno, NKT-1803-03), and the carbon paper (SGL 38BA) is used as cathodic GDL. For separators, the anode separator is fabricated from titanium, and the cathode separator is carbon. The anodic and cathodic flow pattern is designed as single-serpentine channels, and the channel depth, channel width, and rib width are 1 mm ×1 mm ×1 mm, respectively. Results and discussions Fig.1 shows the theoretical and experimental I-V curves. In Fig.1, the electrolysis voltage in both experiment and simulation raises abruptly, which is corresponding to LCD. The experimental LCD is 11.6 A/cm2 as indicated by the black circle, and the predicted LCD is 10.1 A/cm2. Although the prediction of LCD is qualitative, simulation could follow the IV characteristics obtained by experiment before LCD. Fig.2 and Fig.3 shows the effect of operating temperature and pressure on LCD. The electrolysis voltage “E” is experimentally determined, while the gas saturation at interface of PTL-CH “Sg” is obtained through simulation. As shown in Fig.2, the lower operation temperature enlarges the LCD, the experimental LCD increases 8% from 90 ℃ to 80 ℃. Theoretically, high operating temperature increases oxygen bubbles and then rises the gas saturation S g at the anode CL. So, the water supply flowing to CL is insufficient, and the electrochemical performance also decrease. Therefore, the overvoltages caused by mass transport becomes larger in higher operating temperature. As shown in Fig.3, higher operating pressure shrinks the volume of oxygen gas and enhance the water supply from CH to CL, leading to a larger LCD. Under 80 ℃, the experimental LCD rises by 17 % from 0.1 MPa to 0.3 MPa. Although the theoretical analysis reproduced the experimental results in a qualitative manner, the theoretical analysis suggests that, when electrolysis current density is quite close to the LCD, water mass transport at anode reaches a limitation, indicating that water saturation drops to zero at anodic catalyst layer. References Lee J K, et al. Cell Reports Physical Science, 2020:100147. A Zinser, et al. International Journal of Hydrogen Energy, 2019, 44(52): 28077-28087. Figure 1

The locust's steering behavior has long been thought to be achieved under the control of fore‐ and mesothoracic legs before takeoff. This turning strategy is not necessarily present in all steering jumps. It is found that the locust could achieve a large‐angle steering jump without significant yaw rotation beforehand. Herein, how the hindlegs contribute to the steering jump, including kinematic analyses and reaction forces measurement, is studied. It is found that the contralateral hindleg of the turn direction presses down tens of milliseconds earlier than the ipsilateral side. The time lag between both hindlegs is primarily responsible for the steering jumps. The leg kickings with a time lag is induced exogenously by designing sequential electrical stimulation signals for the muscles of both legs. Under 0‐ms, 20‐ms, and 40‐ms time lags, the induced steering angles are 2.1°, 22.1°, and 24.2°, respectively, in the loosely tethered jumps. A locust is transformed into a bio‐robot via a custom e‐backpack and demonstrate a remote‐controlled 20° jump of the bio‐robot. The asynchronous actions of bilateral actuators for steering jumps are extremely beneficial for micro‐robots, as both the jumping and the steering functions can be compacted together.

通过平衡燃料电池和内燃机的优劣势,构建了由燃料电池和内燃机组成的基于替代燃料(氢气、天然气、甲醇、液氨)的混合动力系统,分析了不同系统的发电性能,评估了其技术实现难易程度.结果表明:质子交换膜燃料电池内燃机混合动力系统中,当质子交换膜燃料电池和内燃机燃料流量相同时,该工况下系统的发电效率可达到40％以上;以甲烷为燃料的固体氧化物燃料电池内燃机混合动力系统的发电效率最高,达到了 62.24％,以液氨为燃料的固体氧化物燃料电池燃料消耗率最低,为313.04 g/(kW·h).

Jumping is beneficial for microrobots because they have to face obstacles larger than their height frequently. However, compacting a jumping mechanism into the small body of a microrobot is exceptionally challenging. Instead of assembling a bio-inspired microrobot, the insect itself can be transformed into a jumping robot. Herein, we demonstrated the first-ever biohybrid jumping robot that retained the natural jumping ability of a locust. The fast kicking of the locust's hindleg was mainly induced by two muscles, flexor muscle, and extensor muscle. The elaborate structure and accurate collaboration of the muscles are critical for leg kicking, contributing to the co-contraction process. In this article, we investigated the sequences of muscular activities and demonstrated the co-contraction control exogenously. The kicking control of the hindleg relies on the accurately overlapped stimulation and the independently modulated waveform. With the help of a tiny wireless stimulator, the cyborg locust was remotely controlled to jump an average of 10.4 cm high and 42.6 cm far. Moreover, the cyborg locust retained its internal body righting mechanism, which means the robot can quickly recover its posture for consecutive jumping. This work is a foundational step towards a fully controllable biohybrid jumping robot.

Frogs reveal superior shock-absorption ability, which is mainly brought by the forelimbs. Frogs touch the ground with their forelimbs first in landing, followed by the elbow joints’ compression. In this process, the muscles and tendons of the forelimbs are pulled to store energy. However, muscles and tendons reveal different characteristics in the buffering process. The shock-absorption principle of the frog's forelimbs should be discussed explicitly and systematically on the coordination of muscles and tendons. In this study, we compared the EMG signals of m. anconeus, a primary muscle of frog's forelimb for landing, with the dynamic motions of the forelimb in the landing process. A short muscle potential resting was found around the time of ground touching. Meanwhile, we found that after the frog's toes touched the ground, the movement of the frog went into a buffer stage to absorb impact energy, and the buffering process exhibited different stages, revealing linear and nonlinear characteristics. These results revealed that the forelimb muscles and tendons worked at different times in landing, which formed the different stages. Inspired by the buffering principle of the frog, a bionic shock-absorption mechanism was designed using the torsion springs and dampers. The newly designed mechanism revealed improved buffering performances than the traditional spring-damper devices.

At present, most underwater fuel cell power systems are fed up with pure hydrogen and pure oxygen (FC), which suffers from high capital costs and potential fire hazards. However, all commercial fuel cells are designed in an open-air environment, so it's not available directly. To enhance the range and reduce costs of unmanned underwater vehicles, this paper proposes an underwater energy system of the hydrogen-air fuel cell and battery (FCBS), solving the problems of artificial air intake, exhaust gas treatment and energy management strategy. Employing cruise time, range and mass density as evaluation indexes, the coupling design between FCBS and the key parameters of an unmanned underwater vehicle including the length and velocity, are analyzed contrastively and optimized. The results shows that as the length expands, FCBS can be boosted by over 40 % in cruise time compared to FC, but this advantage fails in very high velocity. Moreover, the optimal velocity for the maximum range of FCBS is 1.4 m/s, and the optimal velocity of FC is 2.0 m/s. Finally, the hybrid system scheme of FCBS is verified by the underwater closed cabin experiments. The results prove the operating feasibility and dependability of the underwater hybrid system with a hydrogen-air fuel cell.