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In embryogenesis and morphogenesis, cell clusters or sheets organize into units of increasing complexity from multi-cell layers, to tissues, organs and eventually whole organisms. Dynamic changes in shape are an essential part of morphogenesis and even the most complex biological structures are formed from fairly simple units through numerous shape transformation steps. Although nature has found ways to elegantly exploit shape transformation in plants and animals, the field is much newer to polymer scientists and engineers. Furthermore, tissue engineers are only starting to explore shape transformation for cell and tissue culture. Current shape changing scaffolds are not permissive of self-folding actuation at arbitrary time points nor are they permissive of step-wise folding, similar to what is observed during morphogenesis and development. The subject of this manuscript is on shape-changing photodegradable hydrogels for cell and tissue culture. We first discuss the physical basis for how light is used to pattern differences in swelling throughout a hydrogel film. The differences in swelling are balanced by the hydrogel’s network elasticity, resulting in folding of free-floating hydrogels. Beyond demonstrating shape-change as a proof of concept, we systematically review the effect of material, chemical, and physical parameters on curvature. Next, we discuss the use of planar sheet geometries and spatiotemporal light patterning to actuate hydrogel folding with different mean and Gaussian curvatures that are relevant for human biology. Finally, we demonstrate that the hydrogels are capable of supporting 2D seeded cell culture and 3D encapsulation. Mammalian cells on the hydrogel scaffolds are shape changed at arbitrary time points and remain viable. We thus demonstrate photodegradable hydrogel shape change as a viable concept for dynamic, 4D cell culture.

3D bioprinting is usually implemented on flat surfaces, posing serious limitations in the fabrication of multilayered curved constructs. 4D bioprinting, combining 3D bioprinting with time-dependent stimuli-induced transformation, enables the fabrication of shape-changing constructs. Here, a 4D biofabrication method is reported for cartilage engineering based on the differential swelling of a smart multi-material system made from two hydrogel-based materials: hyaluronan and alginate. Two ink formulations are used: tyramine-functionalized hyaluronan (HAT, high-swelling) and alginate with HAT (AHAT, low-swelling). Both inks have similar elastic, shear-thinning, and printability behavior. The inks are 3D printed into a bilayered scaffold before triggering the shape-change by using liquid immersion as stimulus. In time (4D), the differential swelling between the two zones leads to the scaffold's self-bending. Different designs are made to tune the radius of curvature and shape. A bioprinted formulation of AHAT and human bone marrow cells demonstrates high cell viability. After 28 days in chondrogenic medium, the curvature is clearly present while cartilage-like matrix production is visible on histology. A proof-of-concept of the recently emerged technology of 4D bioprinting with a specific application for the design of curved structures potentially mimicking the curvature and multilayer cellular nature of native cartilage is demonstrated.

Shape-changing interfaces are tangible, physically dynamic devices which enable user-experience beyond 2D screens. Within Human Computer Interaction, researchers are developing these from low-resolution, low-fidelity prototypes, toward a vision of a truly malleable world. The main focus is in producing and testing hardware, and basic user interactions, which leaves the question unanswered: what are shape-changing interfaces good for? In response, we propose the use of design fiction to investigate potential applications for this technology: to create and analyse artifacts relating to future use-scenarios for shape-change. Whilst research within shape-change often proposes future use-cases for prototypes during discussion, they are seldom in a form that presents them as everyday artifacts. Here, we present and discuss a printed game-play instruction manual for a truly high resolution shape-changing game entitled First Hand, which aims to draw parallels between current gaming practices and the tangible nature of shape-changing interfaces.

We present a design approach for rapid fabrication of high fidelity interactive shape-changing displays using bespoke semi-solid surfaces. This is achieved by segmenting virtual representations of the given data and mapping it to a dynamic physical polygonal surface. First, we establish the design and fabrication approach for generating semi-solid reconfigurable surfaces. Secondly, we demonstrate the generalizability of this approach by presenting design sessions using datasets provided by experts from a diverse range of domains. Thirdly, we evaluate user engagement with the prototype hardware systems that are built. We learned that all participants, all of whom had no previous interaction with shape-changing displays, were able to successfully design interactive hardware systems that physically represent data specific to their work. Finally, we reflect on the content generated to understand if our approach is effective at representing intended output based on a set of user defined functionality requirements.

The shape-changing concept where objects reconfigure their physical geometry has the potential to transform our interactions with computing devices, displays and everyday artifacts. Their dynamic physicality capitalizes on our inherent tactile sense and facilitates object re-appropriation. Research both within and outside HCI continues to develop a diverse range of technological solutions and materials to enable shape-change. However, as an early-stage enabling technology, the community has yet to identify important applications and use-cases to fully exploit its value. To expose and document a range of applications for shape-change, we employed unstructured brainstorming within a public engagement study. A 74-participant brainstorming exercise with members of the public produced 336 individual ideas that were coded into 11 major themes: entertainment, augmented living, medical, tools & utensils, research, architecture, infrastructure, industry, wearables, and education & training. This work documents the methodology and resultant application ideas along with reflections on the approach for gathering application ideas to enable shape-changing interactive surfaces and objects.

The adenylate cyclase stimulator forskolin was used to study the inhibitory effects of elevated cAMP on the activation of washed human platelets loaded with the fluorescent Ca2+ indicator quinl. In the presence of 10 μM isobutylmethylxanthine forskolin inhibited rises in [Ca2+]i evoked by thrombin and platelet-activating factor (PAF) due to both Ca2+ influx and release from internal stores with similar potency. Aggregation evoked by thrombin and PAF was suppressed whilst partial shape-change persisted, even in the absence of a measurable rise in [Ca2+]i. Forskolin did not affect the rise in [Ca2+i evoked by Ca2+ ionophore; aggregation was suppressed but shape-change persisted.

Cytoplasmic free [Ca2+], [Ca2+]i, was measured in human platelets using the intracellularly-trapped, fluorescent indicator quin2. Basal [Ca2+]i with the Ca2+ -ionophore ionomycin revealed apparent thresholds for shape-change, 5-HT release and aggregation of approx. 0.5 microM, 0.8 microM and 2 microM. Thrombin raised [Ca2+]i to 3 microM fast enough for the Ca2+ to have triggered the cell activation. However, thrombin released more 5-HT than ionomycin could, and in Ca2+ -free medium thrombin evoked shape-change and secretion even when [Ca2+]i remained near basal levels throughout, suggesting the existence of alternative triggers for shape-change and secretory exocytosis.