## 1 Introduction
Electromagnetic pulses, external electric fields and those from other indwelling electrical devices can all generate interference. The ability of the implanted devices, such as pacemakers, glucose-monitoring and insulin-delivery systems, neural stimulators, and smart prosthetics, to be easily interrogated by health practitioners also makes these devices vulnerable to hacking [38,39]. In addition to having access to sensitive patient data, the devices can potentially be reprogrammed, interfering with the correct device operations. Therefore, security measures, including security check protocols, firewalls, data encryption and restricted network access should be seriously considered. Application of nano- and molecular-scale technologies for design and fabrication of the implantable circuitry can lead to remarkable advancement in integration density and dynamic power dissipation, enabling neuro-electronic interfacing and nano-bio-robotics [40]. However, current biomedical nanotechnologies are still faced with challenges, such as lower reliability, relatively high stand-by power consumption, and electron leakage due to insufficient insulation. Furthermore, in an effort to improve the resolution of the biological signals being collected, the increasing number of electrodes demands more power to be delivered to the electrode array, thus potentially increasing the thermal energy dissipated within the implant circuitry [41,42]. Given the high cost and time associated with the surgical implantation of the device and the recovery of the patient, long-term reliability of the device is crucial. Peri-implant space is a chemically harsh environment, with the surface of the implant being continuously attacked by the highly conductive and corrosive physiological medium which also carries a variety of biochemically reactive organic molecules. The drive towards small, light and flexible devices may undermine mechanical robustness of the implant; aggressive cleaning procedures used on the devices prior to implantation may further contribute to weakening of the organic layers and adhesives. The ensuing _in vivo_ degradation and loss of integrity may be detrimental to the performance of the device, potentially leading to the device failure, e.g., electrical shorting, and subsequent surgical removal. The implanted device and its degradation by-products may stimulate activation of a range of immune mechanisms, leading to inflammation, which in turn may further contribute to the implant degradation. The toxicity of the leaching ions and fragments may hinder the recovery of damaged tissues adjacent to the implanted device. Surface fouling and infections are also of great concern [43]. The abiotic surface of the implant presents a suitable ground for colonization by human pathogenic bacteria. Once attached to the surface of the device, the bacterial cells may form a three dimensional biofilm, which serves as a protection barrier against detachment, predation by host immune cells and significantly reduces the efficacy of most systemic antibiotics [44,45]. Achieving suitable biocompatibility is a complex matter, due to the dynamic multifaceted nature of the host biological response to synthetic and organic materials used in device fabrication. Where _in vivo_ sensing or stimulation is required for a short period of time, resorbable implantable electronic devices can provide a solution to overcome inflammation and infections associated with long-term implant utilization. The premise is that the materials used in device fabrication are biodegradable, and undergo controlled dissociation over time under normal _in vivo_ physiological conditions. The degradation by-products illicit minimal toxic response and are removed from the peri-implantation site by means of normal metabolic activity [46]. However, fabricating a complex high-performing electronic system from entirely biodegradable, non-toxic set of electronic materials is a difficult undertaking, particularly at small scales.