Bubble casting.pptx

Bubble Casting of robotics is a newly ventured topic that has captured the interests of the soft world domain. Though it cannot completely replace a muscle but it can aid in the movement of the muscles ands limbs.
This is a promising approach for developing soft robotics.

1. Bubble casting Soft Robotics Trevor J. Jones , Etiene Jambon -Pulliet , Joel Marthelot and P.T. Brun Nature; 599 (7884): 229-233, 2021 . Presented by : Raghav Worah

2. The Process Table of Contents Introduction 1 3 Technicalities 4 Merits and demerits 2

3. Introduction The core of biological soft robotics is the ability to move in the environment, which requires actuators capable of generating force. Figure 1:Schematic diagram showing the multi-scale molecular motor assembly used to engineer a biological soft robot. Image courtesy: Annual reviews on Soft Robotics by Adam Finberg al soft r

4. Bubble casting of soft robots include the assembly of a monolithic actuator that is programmed to obey the laws of fluid mechanics. The tubular mould is filled by injecting an elastomeric melt. Then an air bubble is introduced that creates a void Figure 2: Representation of the mould being flooded by the polymer and eventually taking up the shape. Image Courtesy: Nature The flow of the ‘fluid’ in presence of an air bubble will result in the formation of the annulus with a constant thickness. Overall. It would result in the formation of a quasi-uniform film .

5. The process Bubble casting does not require external control and fluid mechanics itself can dictate the movement and cause a change in the shape. The thickness of the membrane is 100µm and the length can go up to a few meters. This thickness is essential as it is the responsible for the response against the inflammation The actuator bends upon its length and adopts a uniform curvature This bending is independent of the length and it increases with increase in elastic shear modulus and thickness of the membrane Overall, upon bending the lower portion of the membrane is under-formed while the upper thin membrane is quasi- isotropicaly stretchable, indicating that the mechanical response of the actuator is due the shape in which it has been casted.

6. Technicalities The flow at the front of the advancing bubble leaves an annulus of constant thickness h where, Ca is the capillary number , R is the radius and µ is the melt viscosity , with U being the bubble velocity and γ being the surface tension. So, the equation stands as : h = 1.34Ca 2/3 R 1+3.55Ca 2/3 h = 3µR (n+1) T w n+1 2 ρ gT c (T c -T m ) n+1 Ratio of viscous to interfacial flow (in polymers) The rate of extrusion through the orifice Finishing time Time of drainage after the reagents are mixed 1/2 Ca =µU/ γ However the thickness of the film would not depend upon the initial thickness of the film. Image Courtesy: Nature Different polymers would result in different thickness owing to the increase in velocity up-to its saturation ( Ca >3)

7. Merits and Demerits This technique is predictive in nature and it could enable the assembly of complex actuators and render their functionality on the basis of the geometrical design. This pneumatic actuator can mimic animal and vegetal movements. It requires sequential moulding procedures and the extent of inflammation required to tailor the shape of the actuator is a tedious process. They cannot perform extremely complex movements Thus, with both merits and demerits in hand, this technique would resonate with the soft matter community and pave newer ways and interventions that would enable in developing next-generation robotic materials with tractable complexity.

8. Thank You