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|Miniature Solid State Batteries for Next-Generation Implantable and On-the-body Medical Devices|
|Keywords: solid state batteries, next-generation implantables, on-the-body medical devices|
|Introduction: The healthcare sector is changing to embrace the interconnectivity of the Internet of Things for more proactive patient health management. The rapid development of sensing devices for Wireless Body Area Networks is opening opportunities for continuous health monitoring in the patient’s home or in the place of care provision. Increasingly energy-efficient, these sensors are following a trend towards miniaturisation to be deployed in implantable or on-the body devices including neurostimulators, leadless pace-makers, smart contact lenses, pulmonary blood pressure monitors … to treat many conditions such as Parkinson’s diseases, Dystonia, chronic pain, OCD, tremors, diabetes, cardiac conditions etc… In most cases, a solution needs to be provided to power these devices autonomously or wirelessly which requires small size, energy storage components such as conventional lithium ion batteries, super-capacitors, solid state batteries, with long life, high reliability, high energy density and bio-compatibility. Methods: The development work presented in this paper aimed to identify materials and processing techniques allowing to produce safe, mm-scale batteries with high energy density and long life. An additional objective was to design a battery that can be packaged and integrated like the rest of the device’s Integrated Components, i.e. that can be soldered or bumped like a “chip” rather than being a cumbersome add-on. Solid state batteries were developed that consist solely of solid components, i.e. the toxic, life- limiting liquid electrolyte was replaced by a thin ceramic film (Beal et al., 2011). These batteries were deposited using Physical Vapour Deposition methods on 6” wafers by evaporation of dense, thin films simultaneously from the elements (for example, cathode LiCoO2 was deposited from Li and Co sources with plasma oxygen)(Beal et al., 2011). The batteries were patterned using laser processing and photolithography and etching techniques to produce thin batteries (< 1 mm) with mm2 footprint and customisable shape. These batteries were tested in demonstration wireless sensor devices. Results: Solid state batteries of variable sizes were produced, down to 15 mm2 footprint and <250 um thickness. The energy density of individual cells was measured to be ~ 2.5 uAh/mm2, regardless of size. Batteries yielded up to 900 cycles down to 80% of their initial capacity and could reliably produce peak currents of more than 5 mA, appropriate for wireless communication, sensing and other micro- processing tasks. Stacked cells could be contained within a thickness of ~1 mm in order to increase energy sufficiently and power an autonomous wireless demonstration sensor. Conclusion: Novel, optimised packaged solid state batteries could enable further development of next-generation medical devices by providing an energy source of minimal size (mm-scale footprint and um-scale thickness), appropriate energy density for increasing functionalities and long life avoiding the risk and cost of removal from implantable or on- the-body medical devices. In this presentation, the audience will be informed about: - The requirements and challenges in designing an energy storage component within medical sensing devices (implantable and non- implantable) in terms of their size and shape; ability to be packaged and integrated with the rest of the other ICs; lifecycle; cost; safety and bio- compatibility; and technical performance (ability to provide energy and power for sensing, communications, data storage) - A review of alternatives for powering such devices autonomously including a comparison of the specifications for the power sources: coin cells, cylindrical batteries, solid state batteries, lithium polymer batteries, other chemistries (Silver- Zinc…), super-capacitors - Alternative for charging these power sources wirelessly through induction or harvested energy|
|Denis Pasero, Product Commercialisation Manager