Life, Bioinspiration, Chemo-Biomimesis and Intelligent Materials

1.1 Introduction

Life is chemistry, but current chemical models, developed from reactions taking place in the gas phase or dilute solutions, are unable to describe life and life functions. Scientists are concerned with the development of theoretical models for the description of life functions, predicting health and diseases, and advancing the different ways for health restoration, even before the emergence of new diseases. In parallel, the progressive development of a new technological world constituted by devices and tools working, as biological organs do, driven by the chemical reactions of the device's constitutive materials should be expected.

1.2 Basic Hypotheses

• Life and life functions originate from chemical reactions taking place in the dense gel of the intracellular matrix (ICM) in living cells.

• Most of the reactions sustaining both life and life functions (such as walking, memory, thinking or consciousness) involve complex organic molecules (enzymes, proteins, nucleic acids and so on) as reactants.

• Biochemical reactions induce specific and convoluted conformational movements (allosteric effects, folding or unfolding) of the organic reactants and, when required for charge and osmotic balance, the exchange of water and ions with the surroundings.

• Current physical or chemical kinetic models do not include any conformational or structural movements induced by reactions.

• Current chemical models were developed from reactions taking place in the gas phase at low pressure, or in solutions using very dilute reactants.

• Gas phase and dilute solutions are far away from the dense reactive gel structure constituting the ICM of living cells.

• Any attempt to describe life and life functions requires advanced chemical models attained from systems where at least one of the reactants is a complex molecule or carbonaceous structure making up part of the dense gel.

• The gel reaction must drive conformational movements of the reactant polymer or macromolecule, and the simultaneous exchange of ions and water.

1.3 Bioinspiration, Biomimesis, Chemo-Biomimesis, Intelligent Materials and Systems

Evolution may be considered the most powerful engineering tool or form of designer machinery that has worked for billions of years to create a plethora of efficient molecules, reactions, structures, cells, organs, functions, systems and beings. These evolutionary molecules have been, and will continue to be, the inspiration of the human species to develop tools, devices, structures, arts, science and technology.

In this context, terms such as bioinspiration, biomimicry or biomimesis, chemo-biomimesis, intelligent materials and intelligent systems appear with rising frequency in scientific papers. Their widespread use has resulted in different meanings when used by different authors and speakers. At this stage, the best possible clarification for some of these concepts may be given by a reference defining the characteristics of the inspiring top-level biological organs or functions and those attained by the new biomimetic material, device or structure.

Bioinspiration: learning from nature's macroscopic, microscopic or molecular structures and being inspired by them to try to adapt physical or mechanical structural efficiency using different materials and scales to solve human problems.

Biomimicry or biomimesis: construction of new tools, devices or robots mimicking some biological physical functions from the extracellular matrix (ECM) of living cells.

Chemo-biomimesis, chemo-biomimicry, electro-chemo-biomimicry or electro-chemo-biomimesis: construction of new chemical- or electrochemical-driven tools, devices or robots mimicking biological functions (from walking or proprioception to consciousness or brain memory) generated by chemical or electrochemical reactions in the ICM of living cells.

Intelligent materials: the most intelligent materials and systems come from nature and are, simultaneously, actuators, sensors and self-healing, e.g., haptic muscles. Artificial intelligent materials are as intelligent as they fit most of these biological characteristics. For those covering the same number of characteristics the most intelligent are those getting the highest efficiency.

In this context the present book is mainly concerned with the exploration of the incipient electro-chemo-biomimetic and chemo-biomimetic scientific and technological space. The emerging scenery is based on new reactive dense gel materials that can mimic, in its simplest expression, the contents of the ICM of living cells from biological organs, including reactive macromolecules, reaction-driven conformational movements, ions and water (or solvent).

A basic, important and differential point related to metals and inorganic materials is that, despite deep change of the material composition (polymer/ ion ratio) during reactions, a relatively low variation of the mechanical consistency is observed, thus maintaining the material's integrity.

Similar composition variations by several orders of magnitude can only be observed inside the functional cells of biological organs when they pass from rest to work states. Reactions involving these artificial dense gels promote variation of the gel (polymer/ion) composition. These material properties, the values of which change with the material composition, are named composition-dependent properties. Parallel variation during reactions involving the composition-dependent properties mimics biological functions. The development of a new technological field giving new chemo-biomimetic and electro-chemo-biomimetic devices and envisaging new tools and robots based on those biomimetic properties is emerging. The state of the art will be presented here.

In parallel, such reactive gels, the reactions of which drive the conformational movement of the reacting polymer chains and structural macroscopic changes, can be taken as a new system and reaction model. New theoretical tools will allow exploration of unknown fields beyond the borders of chemical kinetic models discussed in current chemical, biochemical and biological textbooks. The quantitative inclusion of these reaction-driven conformational and structural changes in present chemical models should result in more advanced structural chemical kinetic models. The theoretical description and quantification of...