6.3 Biomimetic Skin

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and the relationship between voltage and temperature can be calibrated. An analogous

method can be used with semiconductors in P-N junctions. Since P-N junctions are the

basis of several chip building blocks (e. g., for transistors), with the right circuit design

the circuit can function as intended and measure the temperature at the same time.

These measurements are digital, and thus easy to incorporate into an analysis system

as they are in the skin/brain connection.

Pressure-measurements are common on the microscale as well. In that case,

piezoelectric materials are used as already seen in Chapter 5.3 [19–21]. There are a vari-

ety of piezoelectric materials such as perovskites (e. g., [22] and references therein) for

a variety of applications, such as energy harvesting (e. g., [23] and references therein),

high-temperature transducers and actuators (e. g., [24] and references therein), and

tissue regeneration (e. g., [25] and references therein), and more are being developed

(e. g., [26]). Due to the availability of a large amount of piezoelectric materials, there was

no need to use an ion-channel that opens when the surrounding membrane stretches—

a channel that is likely to be difficult to maintain and control in a nonnative environ-

ment.

There are a large number of different “smart”, or environment-responsive, materi-

als that have been reported, some of them containing polysaccharides or proteins. Some

of these examples will be discussed in the following biomimetic skin section, 6.3.

6.3 Biomimetic Skin

The function of skin that has been most often mimicked is touch. This could include sim-

ple piezoelectric materials sensing pressure, as mentioned in the preceding section. But

touch is a lot more complex: Touch also senses surface texture and helps with gripping.

And gripping is automatically adjusted based on the strength of the material and the

weight of the sample. This is important for artificial limbs and robots.

An example for a system that mimics the structure of skin to develop a touch sensor

with a sensitivity approaching that of human skin is discussed here [27] (Figure 6.7). This

sensor includes several design elements of skin: The surface contains ridges that are

Figure 6.7: A touch sensor that mimics the structure

of skin to develop a sensitivity approaching that of

human skin (adapted from [27]).