Ecological Momentary Assessment (EMA) is widely used to study adolescents' experiences; yet, how the design of EMA platforms shapes engagement, research practices, and power dynamics in youth studies remains under-examined. We developed a youth-centered EMA platform prioritizing youth engagement and researcher support, and evaluated it through a case study on a longitudinal investigation with adolescent twins focused on mental health and sleep behavior. Interviews with the research team examined how the platform design choices shaped participant onboarding, sustained engagement, risk monitoring, and data interpretation. The app's teen-centered design and gamified features sustained teen engagement, while the web portal streamlined administrative oversight through a centralized dashboard. However, technical instability and rigid data structures created significant hurdles, leading to privacy concerns among parents and complicating the researchers' ability to analyze raw usage metadata. We provide actionable interaction design guidelines for developing EMA platforms that prioritize youth agency, ethical practice, and research goals.

翻译：生态瞬时评估法（EMA）广泛用于研究青少年的经历；然而，EMA平台的设计如何影响青少年研究中的参与度、研究实践及权力动态，这一问题尚未得到充分探讨。我们开发了一个以青少年为中心的EMA平台，优先考虑青少年参与和研究人员支持，并通过一项针对青少年双胞胎心理健康与睡眠行为的纵向研究案例进行了评估。对研究团队的访谈考察了平台设计选择如何影响参与者招募、持续参与、风险监控及数据解读。该应用以青少年为中心的设计与游戏化功能维持了青少年的参与度，而网络门户通过集中式仪表板简化了行政监督。然而，技术不稳定性和僵化的数据结构造成了显著障碍，引发了家长的隐私担忧，并复杂化了研究人员分析原始使用元数据的能力。我们提出了可操作的人机交互设计指南，用于开发优先考虑青少年自主性、伦理实践和研究目标的EMA平台。