Lee Jae-Hwan, Kim Yoon-Nam, Lee Junsang, Jeon Jooik, Bae Jae-Young, Lee Ju-Yong, Kim Kyung-Sub, Chae Minseong, Park Hyunjun, Kim Jong-Hyoung, Lee Kang-Sik, Kim Jeonghyun, Hyun Jung Keun, Kang Daeshik, Kang Seung-Kyun
Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.
Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.
Sci Adv. 2024 Dec 20;10(51):eads9258. doi: 10.1126/sciadv.ads9258.
Real-time monitoring of infinitesimal deformations on complex morphologies is essential for precision biomechanical engineering. While flexible strain sensors facilitate real-time monitoring with shape-adaptive properties, their sensitivity is generally lower than spectroscopic imaging methods. Crack-based strain sensors achieve enhanced sensitivity with gauge factors (GFs) exceeding 30,000; however, such GFs are only attainable at large strains exceeding several percent and decline below 10 for strains under 10, rendering them inadequate for minute deformations. Here, we introduce hypersensitive and flexible "meta-crack" sensors detecting infinitesimal strains through previously undiscovered crack-opening mechanisms. These sensors achieve remarkable GFs surpassing 1000 at strains of 10 on substrates with a Poisson's ratio of -0.9. The crack orientation-independent gap-widening behavior elucidates the origin of hypersensitivity, corroborated by simplified models and finite element analysis. Additionally, parallel mechanical circuits of meta-cracks effectively address the trade-off between resolution and maximum sensing threshold. In vivo real-time monitoring of cerebrovascular dynamics with a strain resolution of 10 underscores the hypersensitivity and conformal adaptability of sensors.
对于精密生物力学工程而言，实时监测复杂形态上的微小变形至关重要。虽然柔性应变传感器凭借形状自适应特性便于进行实时监测，但其灵敏度通常低于光谱成像方法。基于裂纹的应变传感器在应变片系数（GFs）超过30000时可实现更高的灵敏度；然而，此类应变片系数只有在超过百分之几的大应变时才能达到，而在10以下的应变时会降至10以下，这使得它们不足以用于微小变形的监测。在此，我们介绍了超灵敏且柔性的“元裂纹”传感器，其通过此前未被发现的裂纹张开机制来检测微小应变。这些传感器在泊松比为-0.9的基底上，在10的应变下实现了超过1000的卓越应变片系数。与裂纹取向无关的间隙扩大行为揭示了超灵敏性的起源，简化模型和有限元分析证实了这一点。此外，元裂纹的并行机械电路有效地解决了分辨率与最大传感阈值之间的权衡问题。以10的应变分辨率对脑血管动力学进行体内实时监测，突出了传感器的超灵敏性和共形适应性。
