Electronic artificial “skin

In this chapter we review recent progress of organic transistors for sensor applications. Emphasis is put on large-area, flexible pressure sensors suitable for electronic artificial skin and for photodetectors suitable for sheet image scanners. We also describe future prospects of large-area sensors and the other issues. 

Figure 16.3 shows a circuit diagram of an electronic artificial skin system. Integrated circuits are formed by organic transistors with a pentacene channel layer this has p-type conduction and consists of sensor matrix, column selector, and row decoder. The manufacturing process flow of the sensor matrix has been described above other circuits are processed similarly. 

Fig. 16.3. Circuit diagram of electronic artificial skin consisting of a 16 x 16 access transistor matrix, column selector, and row decoder. The manufactured transistor with pentacene channel layer has p-type conduction. R0-R3 are row addresses, C0-C1 are column...

Fig. 16.4. A measured waveform of electronic artificial skin. When pressure is applied to the sensor matrix, the pressure-sensitive rubber becomes conductive and the bit line is pulled up to the supply voltage. (I) Input signals of...

FIGURE 6.3.2 An image of electronic artificial skin attached on the robot surface. A plastic film with organic transistors, a pressure-sensitive rubber sheet, and a plastic film with top electrodes are laminated together to form a large-area pressure sensor. Some parts of films are removed intentionally to show the inner structures. 

Kawaguchi, H., Someya, T., Sekitani, T., and Sakurai, T., Cut-and-paste customization of organic FET integrated circuit and its application to electronic artificial skin, IEEE J. Solid-State Circuits, 40, 177, 2005. 

In 2004, Someya et al. [24] improved the fabrication technique for these devices and developed an electronic artificial skin. In this work, once again, organic transistors were not used as sensors in themselves but as addressing elements of a flexible matrix which was used to read out pressure maps... 

Fig. 6.9. Electronic artificial skin [24]. Copyright 2004 National Academy of Sciences, U.S.A.

T. Someya. Integration of organic field-effect transistors and rubbery pressure sensors for artificial skin applications. In Electron Devices Meeting, 2003. lEDM 03 Technical Digest. IEEE International, pages 8.4.1-8.4.4, 2003. 

In order to start working on the design of the electronic blocks of the system, the specifications needed for this system to function efficiently for its intended application need to be set. Based on the criteria found in [6], the specification of the robotic finger tip s artificial skin was set, and is found in Table 10.2. 

Richter A, Paschew G (2009) Optoelectrothermic control of highly integrated polymer-based MEMS applied in an artificial skin. Adv Mater 21(9) 979-983 Richter A, Kuckling D, Howitz S, Gehring T, Arndt K-F (2003) Electronically controllable microvalves based on smart hydrogels magnitudes and potential applications. J Microelectromech Syst 12(5) 748-753... 

The presence of polymer, solvent, and ionic components in conducting polymers reminds one of the composition of the materials chosen by nature to produce muscles, neurons, and skin in living creatures. We will describe here some devices ready for commercial applications, such as artificial muscles, smart windows, or smart membranes other industrial products such as polymeric batteries or smart mirrors and processes and devices under development, such as biocompatible nervous system interfaces, smart membranes, and electron-ion transducers, all of them based on the electrochemical behavior of electrodes that are three dimensional at the molecular level. During the discussion we will emphasize the analogies between these electrochemical systems and analogous biological systems. Our aim is to introduce an electrochemistry for conducting polymers, and by extension, for any electrodic process where the structure of the electrode is taken into account. 

Owing to the rapid development of portable personal electronics, flexible electronics has attracted intense interests due to their application in varied fields, such as artificial electronic skin, roll-up displays, distributed... 

A modern prototype of a fully implantable artificial heart contains cutting-edge electronic sensors, synthetic microporous skins, and other novel biomaterials. 

Certain types of heart blocks may be counteracted by an artificial electronic pacemaker which is surgically implanted in the body. The usual procedure is for the surgeon to insert the pacemaker s electrodes, which are connected by wires to the main body of the device, up through a vein and into the heart. Then, the main body of the pacemaker which contains the power supply and the electronic impulse generator is placed under the skin on the chest It is usually necessary to replace the power source every 5 to 7 years. 

Human skin is a fascinating example of a large area sensory system, allowing us to sense temperature, humidity, touch, pressure, and vibration. Scientists are inspired by this natural model system and work on artificial electronic sensor surfaces (Lacour et al. 2005) that will ultimately enable robots with a sense of feeling (Chortos and Bao 2014 Hammock et al. 2013 Bauer et al. 2014). A full coverage of this topic is beyond the scope of this chapter, so here we focus on illustrating the huge potential for piezoelectric polymers in electronic skin development with two selected researeh examples. 

---