Polymer-Encapsulated Single-Chip Implants for Bioelectronic Medicine
Kambiz Nanbakhsh, Wouter Serdijn, Vasiliki Giagka
Session: Body - implant interfacing
Session starts: Friday 25 January, 13:00
Presentation starts: 14:15
Room: Lecture room 559
Kambiz Nanbakhsh (TU Delft)
Wouter Serdijn (TU Delft)
Vasiliki Giagka (TU Delft)
The main goal of bioelectronic medicine is to, one day, replace conventional chemical drugs with miniaturized implants. This way, tiny electrical pulses will be locally delivered to a small group of neurons in order to influence and modify biological functions. Developing such implants, however, has brought many new challenges both in the technological and biological domains. One technical challenge, is packaging such tiny deceives in a way that protects the sensitive electronics inside from the harsh body environment , while, at the same time ensures certain flexibility that allows the implant to conform to the surrounding soft tissue.
Conventionally, medical implants have relied on a titanium (Ti) or ceramic box to protect the inside electronics. Driven by the increased functionality offered by CMOS technologies and the need for further miniaturization, in recent years tremendous efforts have been made in designing miniaturized implants by integrating the majority of components on a single chip . Such a single-chip approach, however, would require novel packaging solutions since the box would consume greater volume compared to the chip and greatly limit the flexibility of the implant. Polymer encapsulation could be an alternative packaging solution which meets the physical constraints needed for bioelectronic medicine [1-2].
One main drawback of polymeric encapsulation, however, is the eventual penetration of water through the polymer. For this purpose, extensive efforts have been carried out on finding thin multi-layer coatings that could delay water and ion penetration and thereby, increase device lifetime . Despite the increased protection offered by these layers, it has been shown that device lifetime can still be reduced when exposed to high electric fields. For example, the authors of  have found that continuous DC biasing of the device reduced the lifetime by a factor of 13 compared to a state where the devices were idle.
In this research, we intend to work towards a single-chip implant by investigating the effect of different electric fields on device lifetimes in soak conditions. For this aim, test structures have been fabricated in standard CMOS technologies and currently being tested in saline. More detailed and up-to-date results will be shared during the conference.