Design of a Metered-Dose Inhaler Actuated by Shape Memory Alloy

[+] Author and Article Information
Brent Utter

Assistant Professor, Department of Mechanical Engineering, Lafayette College, Easton, PA 18042

1Corresponding author.

ASME doi:10.1115/1.4043403 History: Received November 28, 2018; Revised April 01, 2019


The global prevalence of asthma and chronic obstructive pulmonary disorder (COPD) is on the order of hundreds of millions of individuals. The most common treatment approach is to take a self-administered inhaled medication. The current study focuses on pressurized metered-dose inhalers where, unfortunately, rates of mishandling and misuse are extremely high and lead to improper treatment. One significant challenge results from the timing miscoordination of the medicine dispersion and inhalation breath. To address this, the current study demonstrates the feasibility of automating the timing of the medicine dispersion by integrating a Shape Memory Alloy (SMA) actuator and a differential pressure sensor into the casing of a traditional metered-dose inhaler. The approach is to measure the vacuum pressure created by an inspiratory breath, evaluate criteria indicating an acceptable breath, and if those criteria are met, heat the SMA actuator to depress the cartridge and disperse medicine. To meet actuation requirements and reliably depress the inhaler cartridge, two concepts for configuring an SMA wire were designed and compared with respect to complexity, actuation timing, and energy consumption. The proposed concept was able to disperse medicine in 263 ms, averaged over 100 actuations on a single battery charge, facilitating the early dispersion of medicine during an inhalation breath. By describing the design process of an SMA actuated metered-dose inhaler that does not result in a significant increase of its weight or size, this study provides a practical technological approach for reducing the improper treatment of asthma and COPD due to timing miscoordination.

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