Biomedical Engineering Reference
In-Depth Information
to produce compounds capable of performing nontrivial mechanical movements
and exercising a variety of different functions upon external stimulation.
In the previously mentioned address to the American Physical Society (Feynman
1960a,
b
), R. P. Feynman concluded his refl ection on the idea of constructing molec-
ular machines as follows: “What would be the utility of such machines? Who
knows? I cannot see exactly what would happen, but I can hardly doubt that when
we have some control of the rearrangement of things on a molecular scale we will
get an enormously greater range of possible properties that substances can have, and
of different things we can do.” This sentence, pronounced in 1959, is still an appro-
priate comment to the work described in this chapter. The results achieved enable to
devise future developments, which are under investigation in our laboratory: (1) the
design and construction of more sophisticated artifi cial molecular motors and
machines; (2) the use of such systems to do tasks, such as molecular-level transpor-
tation, catalysis, and mechanical gating of molecular channels; and (3) the possibil-
ity of exploiting their logic behavior for information processing at the molecular
level and, in the long run, for the construction of chemical computers.
It should also be noted that the majority of the artifi cial molecular motors devel-
oped so far operate in solution, that is, in an incoherent fashion and without control
of spatial positioning. The solution studies of complicated chemical systems, such
as molecular motors and machines, are indeed of fundamental importance to under-
stand their operation mechanisms; moreover, for some use (e.g., drug delivery),
molecular machines have to work in liquid solution. In this regard, it should be
recalled that motor proteins operate in, or at least in contact with, an aqueous solu-
tion. However, it seems reasonable that, before artifi cial molecular motors and
machines can fi nd applications in many fi elds of technology, they have to be inter-
faced with the macroscopic world by ordering them in some way. The next genera-
tion of molecular machines and motors need to be organized at interfaces, deposited
on surfaces, or immobilized into membranes or porous materials (Álvaro et al.
2003
;
Cavallini et al.
2003
; Long et al.
2003
; Cecchet et al.
2004
; Flood et al.
2004
;
Hernandez et al.
2004
; Huang et al.
2004
; Katz et al.
2004
) so that they can behave
coherently and can be addressed in space. Indeed, the preparation of modifi ed elec-
trodes represents one of the most promising ways to achieve this goal.
Apart from more or less futuristic applications, the extension of the concept of
motor and machine to the molecular level is of interest not only for the development
of nanotechnology, but also for the growth of basic research. Looking at molecular
and supramolecular species from the viewpoint of functions with references to
devices of the macroscopic world is indeed a very interesting exercise, which intro-
duces novel concepts into chemistry as a scientifi c discipline.
Acknowledgments
We would like to thank professors Vincenzo Balzani and Margherita
Venturi for stimulating discussions. Financial support from EU (STREP “Biomach”
NMP2-CT-2003-505487), Ministero dell'Istruzione, dell'Università e della Ricerca (PRIN
“Supramolecular Devices” and FIRB RBNE019H9K), and Università di Bologna (Funds for
Selected Research Topics) is gratefully acknowledged.
