Scaled 3D-printed models of insect outer-ear with tympanic membranes and acoustic trachea preserving key acoustic features.

Katydids (Insecta, Orthoptera, Tettigoniidae) possess a sophisticated foreleg ear with two tympana receiving sound externally through a pinna that acts as a bat detector and internally through an acoustic trachea for conspecific communication. Their miniature scale hinders experimentation, prompting the use of scaled models, yet previous studies have not replicated the full pinna-tympana assembly or the complete acoustic trachea. In this study, micro-CT imaging, AI-assisted segmentation and multi-material 3D-printed assembly were used to generate scaled models. Scaled copies of the pinna-tympanum assembly and the complete acoustic trachea of the neotropical katydid Copiphora gorgonensis were fabricated from high-fidelity reconstructions. Flexible TPU membranes reproduced the expected pressure-driven vibration pattern at the scaled frequency, and when paired with rigid PLA pinnae, they captured the overall outer-ear acoustic response, producing ultrasonic gain within 70-110 kHz that is consistent with the in vivo bat-detection band. Separately, the pressure mapping of the scaled acoustic trachea confirms the spiracle as a filter and the exponential canal as a 17-21 dB amplifier, in line with simulations, consistent with the 1.3-cycle phase shift observed at 23 kHz in living insects. These matching results support the use of scaled biomimetic replicas as reusable, 3Rs-aligned partial substitutes and complements to live-insect acoustic studies in search of bio-inspired applications. Taken together, these outcomes provide a basis for translating the underlying acoustic and structural principles into future miniature engineering systems, including bio-inspired MEMS microphones and compact directional sensors, where passive amplification and filtering remain desirable for improving energy efficiency and signal clarity.