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Understanding the interaction forces between shield-triggered autoinjectors and skin: an in-depth noninvasive study
Anne-Sofie Madsen Staples1,2, Hanaa Abuo-Chalih3, Dan Nørtoft Sørensen2
1Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark.
Expert Opinion on Drug Delivery
|October 2, 2024
Summary
Shorter autoinjector (AI) shields reduce the force users feel during activation by minimizing skin friction. Standing also lowers perceived force, aiding in the development of user-friendly AIs.
Area of Science:
- Biomedical Engineering
- Human Factors Engineering
- Medical Device Design
Background:
- Autoinjectors (AI) are critical for self-administration of medications.
- Understanding the interaction between AI housing and skin is crucial for optimizing user experience and device efficacy.
- Previous research has not fully quantified the force transfer dynamics at the device-skin interface during AI activation.
Purpose of the Study:
- To investigate the interaction between autoinjector (AI) shields and skin during device activation.
- To determine how AI shield design and user positioning affect the force experienced by the user.
- To hypothesize that AI housing absorbs user-applied force based on shield design and skin characteristics.
Main Methods:
- A noninvasive study involving 27 volunteers using a force-measuring test device.
- Measurements included applied force, shield force, and indentation depth relative to shield lengths (2, 4, 6, 8 mm).
- Testing was conducted in both standing and sitting positions, analyzing factors like position and gender.
Main Results:
- Significant differences in force transfer coefficients were observed across various shield lengths, with shorter shields (2 mm) yielding lower coefficients (0.72) compared to longer shields (8 mm, 0.94).
- ANOVA indicated that user position and gender significantly influenced force transfer, with females generally exhibiting lower coefficients.
- Indentation depth increased with applied force and varied significantly with user position, but was not significantly impacted by shield length.
Conclusions:
- Increasing autoinjector shield length reduces skin friction, leading to less force loss and a lower perceived activation force for the user.
- User posture (standing vs. sitting) also impacts force loss, with standing reducing it further.
- These findings on device-tissue interactions are vital for developing improved autoinjectors and minimizing user-related activation failures.
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