A flexible super-capacitive solid-state power supply for miniature implantable medical devices Chuizhou Meng & Oren Z. Gall & Pedro P. Irazoqui Published online: 9 July 2013 # Springer Science+Business Media New York 2013 Abstract We present a high-energy local power supply based on a flexible and solid-state supercapacitor for miniature wire- less implantable medical devices. Wireless radio-frequency (RF) powering recharges the supercapacitor through an anten- na with an RF rectifier. A power management circuit for the super-capacitive system includes a boost converter to increase the breakdown voltage required for powering device circuits, and a parallel conventional capacitor as an intermediate power source to deliver current spikes during high current transients (e.g., wireless data transmission). The supercapacitor has an extremely high area capacitance of ~1.3 mF/mm 2 , and is in the novel form of a 100 μm-thick thin film with the merit of mechanical flexibility and a tailorable size down to 1 mm 2 to meet various clinical dimension requirements. We experi- mentally demonstrate that after fully recharging the capacitor with an external RF powering source, the supercapacitor- based local power supply runs a full system for electromyo- gram (EMG) recording that consumes ~670 μW with wireless-data-transmission functionality for a period of ~1 s in the absence of additional RF powering. Since the quality of wireless powering for implantable devices is sensitive to the position of those devices within the RF electromagnetic field, this high-energy local power supply plays a crucial role in providing continuous and reliable power for medical device operations. Keywords Flexible . Solid-state . Supercapacitor . Miniature . Implantable medical device . Wireless power 1 Introduction Wireless far-field remote powering has the potential to revo- lutionize the world of medical devices. This technology ad- dresses a growing need in the medical device field, and allows for incredible size reductions, which is beneficial in a variety of areas including neural, ocular, and cardiovascular applica- tions (Chow et al. 2010a, 2010b; Ha et al. 2012; Lee et al. 2011; Raghunathan et al. 2011). As a result of recent advances in semiconductor, packaging, and bio-interface technology, state-of-the-art millimeter-sized wireless implantable devices exits or are under development, for clinical applications such as optogenetic stimulator (OGS) for epilepsy (5 mm×10 mm) (Lee et al. 2011; Raghunathan et al. 2011), cardiovascular monitoring (3 mm×6 mm) (Chow et al. 2010a, b), glaucoma intraocular pressure (IOP) monitoring for mouse eye (0.7- mm× 1.3 mm) (Ha et al. 2012) and human eye (3 mm× 6 mm) (Chow et al. 2010a, b), and implantable electromyogram (EMG) electrode (1.5 mm×10 mm) for targeted muscle reinnervation (TMR) control of prosthetic limbs (Bercich et al. 2012). In practice, because the quality of RF powering is very sensitive to the position of the receiver antenna within the RF electromagnetic field, the energy storage component on a chip plays a crucial role in supplying the local power for continuous and reliable operations such as wireless data trans- mission. Thus, there is a strong need for the development of compact energy storage solutions with appropriate size to meet strict clinical dimension constraints while still providing sufficiently high energy for useful operation. Unfortunately, current research on integrating miniature energy storage components on a chip is still inadequate (Chmiola et al. 2010). So far, batteries are the primary choice for implantable medical devices. However, as the size of C. Meng (*) Center for Implantable Devices, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA e-mail: cmeng@purdue.edu O. Z. Gall Center for Implantable Devices, School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA P. P. Irazoqui Center for Implantable Devices, Weldon School of Biomedical Engineering and School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA Biomed Microdevices (2013) 15:973–983 DOI 10.1007/s10544-013-9789-1