Receptogenesis in a Vascularized Robotic Embodiment

TL;DR

This work establishes a materials-based framework for constitutive evolution, enabling robots to physically grow the hardware needed to support emerging behaviors in a complex environment; for example, suggesting a pathway toward autonomous systems capable of generating specialized features, such as neurovascular systems in situated robotics.

Abstract

Equipping robotic systems with the capacity to generate $\textit{ex novo}$ hardware during operation extends control of physical adaptability. Unlike modular systems that rely on discrete component integration pre- or post-deployment, we envision the possibility that physical adaptation and development emerge from dynamic material restructuring to shape the body's intrinsic functions. Drawing inspiration from circulatory systems that redistribute mass and function in biological organisms, we utilize fluidics to restructure the material interface, a capability currently unpaired in robotics. Here, we realize this synthetic growth capability through a vascularized robotic composite designed for programmable material synthesis, demonstrated via receptogenesis - the on-demand construction of sensors from internal fluid reserves based on environmental cues. By coordinating the fluidic transport of precursors with external localized UV irradiation, we drive an $\textit{in situ}$ photopolymerization that chemically reconstructs the vasculature from the inside out. This reaction converts precursors with photolatent initiator into a solid dispersion of UV-sensitive polypyrrole, establishing a sensing modality validated by a characteristic decrease in electrical impedance. The newly synthesized sensor closed a control loop to regulate wing flapping in a moth-inspired robotic demonstrator. This physical update increased the robot's capability in real time. This work establishes a materials-based framework for constitutive evolution, enabling robots to physically grow the hardware needed to support emerging behaviors in a complex environment; for example, suggesting a pathway toward autonomous systems capable of generating specialized features, such as neurovascular systems in situated robotics.

Figures (4)

• Figure 1: Ex novo hardware (receptor) generation in a moth-inspired vascular system: system concept a) Biological model. Dorsal view on Catocala fraxini, scales removed on the right wing to visualise wing veins. The SEM image inset shows a cross-section of a wing vein for carrying hemolymph. b) System components of a natural and artificial open circulatory system, respectively. Connectedness is achieved with directing fluid flow and interaction with internal elements. c) Receptogenesis concept. Precursors introduced on demand to the vasculature form a receptive area in response to an externally applied stimulus. d) The local physical update gives access to receptor data (left) that closes emergent control loops, exemplified by regulating the flapping of artificial wings (top right) or visual signalling (bottom right). Scale bars (a) - 1cm, (a, inset) - 100µm
• Figure 2: Multiscale vascularization. a) Vascularization hierarchies - global transport (FDM) and local interaction (infusion). b) Photograph and cross-sectional drawing of a global vascularised robotic composite consisting of veins and microchannels. c) SEM images of a non-infused structure, complementary space between the individual infill lines form a network of microchannels. d) SEM images of an infused (and thereafter dried) structure. Scale bars: (b, main) - 1mm, (b, inset) - 10mm, (c, d, main) - 100µm, (c, d, insets) - 10µm
• Figure 3: Receptogenesis based on PPy in situ photopolymerization a) The receptive area forms by local UV-exposure of the structure with precursors from the chemical inventory and distributed by a vascular system. b) Scheme of PETG infusion with precursors and in-situ photopolymersiationon stimulated by an external UV light source (at 365nm) (top). Transilluminative snapshots of photopolymerisation, where PPy synthesis is evidenced by the darkening (bottom). c) 580nm transmittance through the receptive area decreases during photopolymerization, corresponding to nuclear growth of PPy clusters (insets). Black and grey lines correspond to two representative photopolymerization instances. d) UV-PPy photolithography demonstration on structure infused 7 days prior. e) UV induced temporary (bi)polaron: reaction scheme. Adapted from Bredas1985PolaronsPolymers. f) Embedded receptor: implementation using impedimetric readout (left) and demonstration (right). g) Impedimentric transient response (black) of receptive area to UV irradiation (blue) and modulated optical readout of the receptor (red). Scale bars: (b, d) - 1cm
• Figure 4: Illustrative robotic demonstration of ex novo hardware genesis. a, b) System implementation: a) scheme showing the fluid, control, and power lines and b) photograph. c, d) Illustrative filling of vascular system: c) air displaced with isopropanol (superimposed timestamps) and d) isopropanol displaced with isopropanol:water with blue tracer (sequential snapshots of top and isometric view) e) Wing-scale receptogenesis. f) The robotic moth reacts to UV-exposure to a receptive area in the thorax section by activation of the wing flapping mechanism and visual indication (LED flashing). Scale bars: 1cm