By Mark Russell

In the world of medical electronics, the title for biggest breakthrough goes to closed loop functionality. This technological milestone has helped device designers achieve new levels of active implantable performance, and it has driven change in three crucial areas: power conservation (providing stimulation only as needed through neural feedback), improved patient efficacy (adjusting therapy based on changing patient condition), and better feedback tools (communicating real-time information via wireless to doctors).

Closed-loop devices, such as those used to control epilepsy, for example, use implantable multi-electrode arrays and amplifiers to record electrical signals. These signals can be used to predict a seizure, and can even apply preventative electrical stimulation in advance.

A depiction of the “high density vertical array” concept, which uses multiple Bal Conn™ electrical contacts to reduce package size and increase functionality in an active implantable device. Callouts reference patent descriptions.

This closed-loop functionality in active implantables requires optimal power efficiency and signal isolation, and much of this is dependent upon the performance of electrical contacts and contact systems used to connect leads to batteries and electronics. Highly conductive and space-efficient components, such as the Bal Conn electrical contact and the SYGNUS Implantable contact system — both offered by Bal Seal Engineering — are supporting advanced connection arrays and signal isolation requirements of closed-loop, high-connector-count arrays.

The SYGNUS system incorporates fluidic sealing technology into the discrete connection which, in turn, supports quick integration and eliminates the need for OEMs to source, manufacture or test separate seals. The Bal Conn, itself a stand-alone contact technology as well as the platform on which SYGNUS is built, can accommodate lead diameters as small as 0.9 mm. A 0.64 mm version is currently under development.

With the use of closed-loop devices becoming more widespread, the ability to support smaller footprint connections for active implantables in a proven and reliable design will become increasingly critical. To address this, Bal Seal has developed a new subassembly concept to help engineers dramatically improve device functionality while reducing overall package size. The concept, which can incorporate a “cap” or cover design, uses vertically positioned pins or rods of varying diameters to double or triple the amount of connections available to the device lead. It can be engineered to minimize insertion force issues that present challenges in serial arrays with small leads, and it offers designers new opportunities for improved contact density.