Proposal Number: 1247526 P.I.: Emami-Neyestanka, Azita
This proposal explores a new class of microelectrode arrays, Instead of having one large chip that gets connected to the electrode array via a dense cable, many tiny low-cost chips that form a complete system are distributed over a foldable substrate along with the electrodes. The location of the chips and the electrodes will be optimized through the design of the origami structure. The electronic chips will have efficient capacitive sensors that not only can determine the proximity of the chips, but also help to reconfigure the chips/sensors to establish optimum communication links between the chips. The origami structures will have a number of important properties, they: 1) can be folded (e.g. rolled into a cylindrical shape) for insertion into the human body through minimally invasive procedures; 2) will self-deploy when they are released within the human body; 3) will take up unique curved shapes that precisely match the organs to be stimulated.
In this project we focused on design and developement of novel origami retinal implants that are minimally invasive and can take the shape of the eye. To achive these goals, we developed a theoretical model and design algorithm for constructing spherical surfaces via folding. The output of this model was used as the input for both experimental fabrication and for detailed numerical modeling that included material properties, thicknesses, and other non-idealities. As a first example we presented an origami solution that takes a spherical shape and matches the eye contour. We then developed a general numerical simulation technique for origami folding and used this technique to study the retinal implants made by the origami technique. Our simulation computes the final shape of the implant, the stress and strain distribution in the implant during construction, and the pressure forces applied by the implant onto the retina. Using this simulation, we have been able to examine the separation between the surface of the implant and the retina, considering spherical retinas of different diameters. Another important outcome of this project was actual fabrication of the Parylene-C origami structure and development of the folding method. Due to its high biocompatibility, good mechanical strength and machinability, parylene-C (PA-C) was determined to be a good candidate for the material of implantable devices. In this work we presented our method of folding a fully-released 2D parylene-C thin film with the special folding crease patterns to a 3D spherical origami structure. Finally, our origami implant design is a 3D integration technique which addresses size and cost constraints in biomedical implants with distributed ICs at the heart of the design. To achieve these goals, we designed a capacitive proximity interconnect scheme that enables chip-to-chip communication across folds in the origami implant, allowing increased flexibility of chip placement and orientation. The capacitive plate array senses link quality and chip-to-chip alignment, and adapts the data rate at each plate accordingly, shutting down poorly-coupled links to save power. Instead of using separate plate arrays for alignment sensing and communication, this interconnect embeds the alignment sensor and transceiver arrays within the same set of plates, so that link quality can be measured at the communications plates directly, thus simplifying their adaptation to alignment. In order to save power and area, the sensor circuitry is distributed across the array and shares functional blocks with the transceiver. Data rates from 10-60 Mbps are achieved over 4-12 μm of parylene-C, with efficiencies up to 0.180 pJ/bit.
