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Abstract Morphing matter that change shapes and properties in response to external stimuli have gained significant interests in material science, robotics, biomedical engineering, wearables, architecture, and design. Along with functional advances, there is growing pressure and interest in considering the environmental impact of morphing matter during its life cycle. The unique manufacturing and usage of morphing matter means that existing sustainable design frameworks and principles for general physical products may not apply directly. For example, manufacturing morphing matter often requires designing and predicting materials' behaviors over time, and using devices fabricated with morphing matter often involves harnessing renewable energy and self‐reconfiguration, which pose unique sustainability opportunities and challenges. This study reflects and summarizes the field's practice in sustainable manufacturing, transport, use, and end‐of‐life handling of morphing matter. The term “sustainable morphing matter” (SMM) is coined, suggesting that sustainability‐conscious factors can become an integral component of morphing matter. In addition, ways to apply sustainability‐conscious factors to augment the existing design pipeline of morphing matter are presented, and more quantitative and algorithmic‐level developments are needed to apply these factors rigorously to the design process. 

Single-walled carbon nanotubes (SWCNTs) are increasingly being investigated for biomedical imaging, sensing, and drug delivery. Cell types, cellular entry mechanisms, and SWCNT lengths dictate SWCNT uptake, subsequent intracellular trafficking, and retention. Specialized immune cells known as macrophages are capable of two size-dependent entry mechanisms: endocytosis of small particles (diameter < 200 nm) and phagocytosis of large particles (diameter > 500 nm). In comparison, fibroblasts uptake particles predominantly through endocytosis. We report dependence of cellular processing including uptake, subcellular distribution, and retention on the SWCNT length and immune cell-specific processes. We chose SWCNTs of three different average lengths: 50 nm (ultrashort, US), 150 nm (short) and 500 nm (long) to encompass two different entry mechanisms, and noncovalently dispersed them in water, cell culture media, and phosphate buffer (pH 5) with bovine serum albumin, which maintains the SWCNT optical properties and promotes their cellular uptake. Using confocal Raman imaging and spectroscopy, we quantified cellular uptake, tracked the intracellular dispersion state ( i.e. , individualized versus bundled), and monitored recovery as a function of SWCNT lengths in macrophages. Cellular uptake of SWCNTs increases with decreasing SWCNT length. Interestingly, short-SWCNTs become highly bundled in concentrated phase dense regions of macrophages after uptake and most of these SWCNTs are retained for at least 24 h. On the other hand, both US- and long-SWCNTs remain largely individualized after uptake into macrophages and are lost over a similar elapsed time. After uptake into fibroblasts, however, short-SWCNTs remain individualized and are exocytosed over 24 h. We hypothesize that aggregation of SWCNTs within macrophages but not fibroblasts may facilitate the retention of SWCNTs within the former cell type. Furthermore, the differential length-dependent cellular processing suggests potential applications of macrophages as live cell carriers of SWCNTs into tumors and regions of inflammation for therapy and imaging.