MOSFET, but in its successor, the so-called FinFET, and its critical dimensions will

decrease in the range of a few nanometers in the 2020s. However, the doubling of mi­

croelectronic chip performance in a 1.5–2-year cycle continues unabated – and can be seen

by all of us regularly when buying new electronic equipment.

Medical implants with microelectronic components have been in use for decades as

pacemakers, defibrillators, and cochlear implants for the treatment of heart disease and

extreme hearing loss. In addition, so-called wearables, which are worn on the body to

continuously track body functions and fitness parameters like heart rate, body tem­

perature, blood pressure, respiration rate, blood oxygen content, deep sleep phases,

etc., have become widespread in recent years. Most developments in the use of micro­

electronics for monitoring bodily functions have been in the field of biosensors. For a

large number of analytes, it would be extremely interesting to follow the spatiotemporal

distribution patterns in the body directly in vivo. This applies in particular to glucose

dissolved in the blood, from whose deviations from the normal range (3–5 mMol/L)

millions of diabetes patients suffer worldwide. In addition to implantable glucose sen­

sors [7–11], sensors are also being developed for other analytes such as lactate, creatine/

creatinine, ethanol [12], O2, NOx, etc.

The purpose of these systems is to detect deviation of the analyte from its normal range

and to help patients maintain the physiologically beneficial state. In addition, the devel­

opment of microelectronic implants has already begun not only for diagnosis but also for

therapy, of which the insulin pump is a good example [13]. The developments to be pre­

sented are always about assistance systems for maintaining the patient’s health. The tech­

nology drivers here are the high degree of miniaturization, i.e., the extreme reduction in the

form factor, and the greater comfort for the patient that microelectronics makes possible.

Various reviews are available on the subject of microelectronic human implants, cov­

ering the aspects of biocompatibility [14] or network issues of a body-area network [15].

This work concentrates on Si-based microelectronics, although polymer microelectronics

can now also be produced and are becoming increasingly important [16,17]. However,

some findings, especially those concerning system architecture, concern bioelectronic

implants in general, independent of the material used. The paper does not focus on

cardiovascular or cochlear implants, but gives an overview of ongoing research and

developments for future systems.

Another fundamental observation relates to the degree of integration of bioelectronic

systems into the body. Many of them must be called semi-implants, since for them only

the sensor or actuator chip is in contact with the corresponding tissue, and other

components are attached extracorporeally. This is the case, for example, with cochlear

hearing aids, current glucose sensors, or systems for peripheral nerve stimulation

(PNS), in which the transponder or power supply are often not implanted as well.

Cardiac pacemakers and derived systems, especially, have reached the level of full

implants, where in addition to sensor and actuator functions, transponder and energy

supply are also implanted into the body.

First, current examples of sensor and actuator chips are presented, of which functional

samples have already been implanted. Also, systems will be considered that are developed

for veterinary medicine. Since the application environment in other mammals is very si­

milar to that in humans, some of these are precursor models whose human application is

subsequently envisaged. The presentation of the microchips is followed by other modules

that are essential for the overall system: the controller and communication chip as well as

the power supply and system integration. Figure 21.1 shows an implantable overall system

with its components [18]. The paper concludes with a discussion of the societal constraints

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