7 Future Developments

This book is about human senses and movement, how they function on the nanoscale,

and how they can be mimicked on the nanoscale by technology. As we have seen, hu-

man and human-made sensors always have several elements: the sensing or detection

element, the transducer, possibly an amplifier, and an analysis element.

The human sensing elements, eyes, nose, ears, and the mechanical and temperature

sensors in skin, are connected to receptors or ion channels as transducers that change

the original signal into an electrical signal. This initiates an action potential, which is

sent to the brain for analysis and possible action/reaction based on need or memory/ex-

perience. In technology, sensors work in very much the same way. The sensing element

is translated into an electrical signal that is sent to a computer for analysis and recog-

nition. Nowadays, computers might even remember the signal or a signal pattern and

learn from that “experience”.

Human motion is based on two stiff, molecular molecules, one that is the “street”,

and the other that uses energy to “walk” on that street. A large amount of these molecules

combine in a muscle. The duration and the strength of muscle contraction can be con-

trolled in this system by controlling these molecules. In nanotechnology, these molecules

have been successfully used to transport nanosized cargo. The system can now in a few

cases be automated—with the exception of loading the cargo onto the motor protein. Ini-

tial work has been successful in scaling up movement by self-assembly, but the problem

of large-scale and long-duration movement has not yet been solved. Mimicking motion

with other chemicals is still in its infancy, since there has not been an effective street/mo-

tor connection developed with the exception of rotaxane-based molecules. But those

molecules limit motion to a few nanometers and do not allow for continuous, linear

motion. Some self-assembled systems using DNA or vesicles are trying to create con-

trolled larger-scale movement in tubes. Rotary motion is easier with chemicals, but it is

difficult to connect these chemicals to a controlled energy source.

In the eyes, the human photoreceptors, detection occurs via a change in the three-

dimensional structure of a molecule. The change in shape initiates a signal cascade that

amplifies the signal and transfers the signal to the brain. Using the actual molecules in

the process for nanosized photosensors is difficult, and has only rarely been successful.

There is a large variety of nanotechnological photosensors. They range from chemical

or electrical sensors that measure a change in light absorption to fluorescence sensors

where a chemical or current is reported as a color change. What is less common is that

sensors are connected to amplification and analysis within one system. Phototransistors

are trying to start to achieve that integration. Another function of human system has

been mimicked, however—the constant movement of the eyes to create a more accurate

picture and to help with the analysis of it. Combining all of these properties would make

for a much more powerful photosensor in the future.

Smell and taste have been mimicked most often, and chemical sensing methods are

the furthest developed among approaches to replicating theses senses. These methods

https://doi.org/10.1515/9783110779196-007