Integrating Solid State Micro-Batteries in Low Power, Miniature Medical Devices

Product design and overall shape and size of miniature sensor systems are often limited by the energy storage device supplying power to the system. This is especially true in the case of miniature medical devices designed for use on or in the human body. A special case of this is ophthalmic sensing and therapeutic devices that by their very nature demand that the device is extremely small and unobtrusive. For example, electronic contact lenses have been designed for vision correction and enhancement and other purposes to improve quality of life. Cymbet’s EnerChip rechargeable batteries are designed to overcome the limitations inherent in integrating batteries in devices where shape, total area, and thickness are all critical to the overall product design. EnerChips, which can be as small as 1mm2 footprint and <0.2mm thickness in a bare die format, are made using semiconductor manufacturing methods. Storage capacity is proportional to the area of the cell. These solid-state batteries can be attached to rigid and flexible substrates using conventional flip-chip methods by way of gold bumps, solder, and anisotropic conductive films. This approach greatly reduces the overhead associated with connecting the power source to the circuit while ensuring a robust connection. Moreover, the shape of these micro-batteries can be customized using techniques similar to those used in integrated circuit design. This approach allows product designers to place one or more batteries in locations within the lens that provides for easy routing of circuit connections while not obstructing vision or causing discomfort to the user. With ultra-low power electronic components now in the mainstream, and because the EnerChips are rechargeable, there are numerous practical applications for electronic lenses. Recharging can be done wirelessly – through NFC power transfer, for example. In addition, EnerChips are bio-compatible, making them well suited for incorporation into miniature medical devices to worn on or placed inside the body.