Date of Award

Spring 2025

Document Type

Thesis

Department

Mechanical Engineering

Abstract

Gun violence in the United States, particularly unauthorized firearm use by children and impulsive suicides, remains a devastating public health crisis. Despite widespread use of gun safes and locks, many remain ineffective or inconvenient, with most unauthorized users accessing firearms that were either unlocked or secured with easily bypassed mechanisms. Biometric locks present a promising alternative, but existing products often fall short in speed, reliability, and usability. To address this gap, we developed Trigger Buddy, a biometric handgun lock designed to balance accessibility, durability, and security. Trigger Buddy mounts directly to a handgun's picatinny rail and uses a fingerprint sensor to rapidly unlock sliding steel doors covering the trigger well. Through iterative design and testing, we engineered a modular system with a steel-reinforced composite door, ergonomic housing, and a rack-and-pinion locking mechanism, all powered by a microcontroller and 9V battery. Our experiments demonstrated that Trigger Buddy meets critical performance metrics: unlocking in under 1 second, withstanding 100 lbf of prying force, and showing no statistically significant impact on shooting accuracy. The fingerprint scanner maintained a false rejection rate under 2% (excluding pinky fingers), and the total system weight remained close to the 1 lb target. Finite element analyses and physical four-point bending tests confirmed structural integrity under realistic loads. Trigger Buddy offers a secure, rapid-access solution for firearm owners, especially parents concerned with child safety. Its modular design and integration with standard firearm interfaces allow for ease of adoption. However, reliability under environmental stress (e.g., wet or dirty fingers) and long-term durability require continued refinement before commercial release. To ensure widespread utility and ethical impact, we recommend future iterations improve biometric robustness and reduce cost through manufacturing optimizations. Pursuing California DOJ certification is critical for market entry. Ultimately, Trigger Buddy demonstrates how innovative engineering can address real societal issues, bridging the gap between security and accessibility in firearm safety.

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