Biocompatibility memory devices

New natural polymers based on synthesis from renewable resources, improved recyclability based on retrosynthesis to reusable precursors, and molecular suicide switches to initiate biodegradation on demand are the exciting areas in polymer science. In the area of biomolecular materials, new materials for implants with improved durability and biocompatibility, light-harvesting materials based on biomimicry of photosynthetic systems, and biosensors for analysis and artificial enzymes for bioremediation will present the breakthrough opportunities. Finally, in the field of electronics and photonics, the new challenges are molecular switches, transistors, and other electronic components molecular photoad-dressable memory devices and ferroelectrics and ferromagnets based on nonmetals. 

Overall, much effort has been made to develop biocompatible organic materials, which allows for the ultimate integration between the electronic device and biological system. The possibility of fabricating memory devices on biodegradable substrates, such as, rice paper and chitosan is also demonstrated. Biocompatible and flexible resistive switching memory devices are made on the basis of Ag-doped chitosan as the natural solid polymer electrolyte layer on the transparent and bendable substrate. Decomposable devices, where chitosan layer serves as the substrate while Mg as the electrode, have been also achieved (Hosseini and Lee, 2015). A comparison of the biocompatible material-based resistive switching memory devices is made in Table 3.2. 

Table 3.2 Comparison of Biocompatible Material-Based Resistive Random Access Memory Devices...

In this section, the sterilization and biocompatibility of SMPs are discussed jointly. All proposed SMP medical devices evenmally have to be validated with a designated sterilization method before they can be used clinically. The method of sterilization can influence the biocompatibility and performance of a device [104, 105], Subsequently, sterilization can also alter the thermomechanical properties of the polymer, which directly influence shape-memory properties such as shape storage (fixity) and recovery [106]. Currently, there are three types of sterilization methods including heat, radiation, and chemical techniques. 

Once an SMP device is implanted within the body and fully activated, the device ceases to be shape-memory and should have the properties of a typical polymer-based device and are subject to all the same long-term performance concerns. Obviously, long-term biocompatibility and carcinogenicity are a concern of implantable polymeric materials however, mechanical properties of polymers with respect to water absorption and biodegradation will be discussed for the remainder of this chapter. 

It is unknown which of the proposed devices presented in this chapter will overcome the regulatory and commercial barriers and be accepted into the marketplace. However, the literature not only shows promise in future SMP biomedical devices, but several working devices proven in regards to biocompatibility and animal studies. Future proposed SMP devices will likely require multiple functionalities including triple shape-memory, remote actuation, therapeutic agents, tailored degradation rates, surface modifications, and more. 

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