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This paper seeks to present recent work demonstrating the feasibility of Microbots' mobility in rough terrain. Microbots are a new search and rescue concept based on the deployment of teams of small spherical mobile robots. In this concept, hundreds to thousands of cm‐scale, sub‐kilogram Microbots are released over a search site such as collapsed building rubble or caves. Microbots use hopping, bouncing, and rolling to infiltrate subterranean spaces in search of possible survivors.

The feasibility of the Microbot mobility concept is evaluated through laboratory prototypes and mobility simulations.

Experimental studies have demonstrated the feasibility of using dielectric elastomer actuators (DEAs) to generate autonomous hops. High‐efficiency hydrogen fuel cells were shown to be able to power DEAs. Simulation results show that Microbots of proper diameter and hop height can successfully traverse very rough terrains.

The implication of this research is that small hopping robots are appropriate for certain search and rescue missions. The limitation of the research to date is that issues of control, path planning, and communication have not yet been addressed.

Key technologies of the Microbot mobility, that use high‐energy‐density micro fuel cells combined with low cost and lightweight DEAs, are feasible. These technologies have the potential to make a significant impact on the search and rescue robots.

These results suggest that a team of Microbots‐based DEAs and micro fuel cells can be a useful and effective tool for search and rescue operations.

This study aims to focus on roughening N-face (backside) GaN substrate prior to GaN-on-GaN light-emitting diode (LED) growth as an attempt to improve the LED performance.

The N-face of GaN substrate was roughened by three different etchants; ammonium hydroxide (NH4OH), a mixture of NH₄OH and H₂O₂ (NH₄OH: H₂O₂) and potassium hydroxide (KOH). Hexagonal pyramids were successfully formed on the surface when the substrate was subjected to the etching in all cases.

Under 30 min of etching, the highest density of pyramids was obtained by NH4OH: H₂O₂ etching, which was 5 × 10⁹ cm^–2. The density by KOH and NH₄OH etchings was 3.6 × 10⁹ and 5 × 10⁸ cm^–2, respectively. At standard operation of current density at 20 A/cm², the optical power and external quantum efficiency of the LED on the roughened GaN substrate by NH₄OH: H₂O₂ were 12.3 mW and 22%, respectively, which are higher than its counterparts.

This study demonstrated NH₄OH: H₂O₂ is a new etchant for roughening the N-face GaN substrate. The results showed that such etchant increased the density of the pyramids on the N-face GaN substrate, which subsequently resulted in higher optical power and external quantum efficiency to the LED as compared to KOH and NH₄OH.