As student at the University of Paris, I was attracted by both the rigor of physics and the creativity of chemistry, so I got two Master of Science degrees, one in Physics and one in Chemistry. I then got my Ph.D. in Physical Chemistry. I was fortunate enough to attain the rank of Professor when I was 31, and kept on working in a lab there. Then, around 1980, I was offered the possibility to create my own lab. I was very enthusiastic, as I wanted to make use of my multidisciplinary training in physics and chemistry and I decided to explore a newly emerged area: organic conjugated polymers. At that time, two main conjugated polymers had appeared in labs, polyacetylene and polypyrrole. These polymers were shown to switch between two states, one neutral insulating, and the other oxidized and electrically conducting.

Polyacetylene showed, however, to be highly unstable toward air and humidity, and polypyrrole was only stable in its oxidized conducting state. At that time, I thought that any interesting development of such classes of polymers required them to be environmentally stable in their both neutral and conducting state. Furthermore, as a chemist, I thought it would be interesting to be able to modulate the properties of the monomers, and consequently those of the polymers, by subtle chemical substitutions on the monomers. Finally, one important drawback of unstable polymers was the fact that the equipment of my lab was miserable, and I didn’t have a glove box for working in a controlled atmosphere.

So in 1981 and 1982, I proposed, for the first time in the literature, "polythiophenes" which were electrochemically synthesized. These polymers were very stable in both states, and I spent a lot of time in conferences and in meetings from 1982-1984 convincing other research labs that, besides the still highly worked polyacetylene, polythiophenes were very attractive, owing to their stability and their versatility associated with the various chemical substitutions which could be performed on the monomers. The field of polythiophenes finally started around 1984, and has consistently increased since then.

At that same time, I was already interested in the neutral state of polythiophenes, which showed a very long-term stability (it was the only stable neutral polymer at that time), and which showed to be in fact an organic semiconductor. So, our first publications on the photovoltaic properties of polythiophenes stem from 1984. Many labs joined this field of organic semiconductors based on conjugated polymers, but results were deceiving: almost all labs found that these polymers were very bad semiconductors, by a factor of about 105, in terms of carrier mobility, when compared with the poorest inorganic semiconductor in practical use, amorphous silicon.

So in the late ‘80s, after tremendous work on these materials, most labs came to the conclusion that these conjugated materials could never reach the level for use as active semiconducting layers in real devices (no foreseen application). Physics considerations led me to think, however, that purity and material structure should be the keys for improving these materials, and against the beliefs and ways of research at that time, I decided to work not on longer and longer conjugated polymers, as was done in most labs, but on very short but well-defined conjugated oligomers (defined short segments of the parent polymers).

I was thus able to show for the first time, in 1990, that short conjugated oligothiophenes, e.g., sexithiophene, showed a mobility that was increased by a factor of 104 when compared with the parent polythiophenes. At that time we published the first polymer-based device, which was shown to be flexible, i.e., "flexible polymer electronics." I am very proud of this 1990 publication, as some other labs tried afterwards (1993) to claim the first flexible device, but I was the first one to realize and to analyze such a device, and to point out the potential interest of their flexibility. It must be said that at the same time, R. Friend also demonstrated that another polymer, PPV, showed electroluminescent properties (OLEDs). These two innovations, which came out about the same time, launched a very important research effort in many labs, both in universities and in companies. The decisive step we performed in the improvement of mobility was then analyzed and interpreted in our lab. In that period (1990-3), I had many contacts with companies to which I explained my research, principally Lucent-Bell Labs and IBM. I also had a common research contract with the Philips Company in the Netherlands, to which we explained in great detail the complete sequence for making these polymer-based transistors. Afterwards, these companies went on their own, Lucent being very fair and citing our work, whereas Philips, although having learned everything from us during two years of contract, decided to ignore us in their work and in their citations. But c’est la vie. In a further step, I decided to make full use of the organic character of the materials involved in the fabrication of these devices, and I performed the first demonstration, in 1994, showing that a device could be realized with the sole use of printing techniques. This work, published in Science (1994), was quoted in the front page of the New York Times and this information was then reproduced all over the world. In the past months, other printed devices have been proposed in the literature, which confirm the new route I pioneered some seven years ago.

A further area in which I have been involved concerns the previous research theme of conjugated polythiophenes, which I progressed towards the functionalization of polythiophenes. In this sense, I considered these conjugated polymers as a tridimensional network of macromolecular electrically conducting wires, able to transport information from recognition centers, which can be covalently bonded along the polymer chains, through the chemical modification of the monomers. I developed, in 1989, the concept of "intelligent materials" (the first time this word was introduced in the literature, and I had to argue with the editor of Angewandte Chemie to convince him to accept this terminology). So we first developed ion sensors by grafting crown ethers, i.e. selective ion complexants, along the polythiophene chains.

Around 1991-92, I also decided to make an important move toward biology, and to develop electrochemical sensors for peptides, enzymes, DNA, and antibodies. The potential interest of this new class of sensors is to afford an electrical response, which flows from the recognition center (analogous to a receptor) through the conjugated conducting macromolecular chains (analogous to nerves) toward the electrode/computer (analogous to the brain). So these systems afford a direct real-time reading of the information, which can be stored and processed in a computer associated with the electrode, in the image of a living species.

To sum up, I think that the moves I made in my scientific activity have been mainly governed by:

i) My multidisciplinary training at the University. This is a necessary condition for developing the theme of Materials Science, which requires a deep knowledge in a very broad range of disciplines, starting from synthetic chemistry, through physical chemistry and up to physics and electronics.

ii) The aim to understand molecular material characteristics in terms of molecular properties, allowing thus the control of and the tuning of these material characteristics

iii) The goal to bring the versatility of chemistry and the power of chemical synthesis to the field of electronics

iv) To keep being inspired by the beauty and power of the organization existing in living species (sensing, intelligence), and to try to mimic it in controlled three-dimensional man-made architectures.

My actual research goals are concentrated toward the biological recognition of DNA and antibodies, and also toward the use of organic semiconductors for building new types of solar cells, as I think, as scientists, that we have the responsibility to work for the future, 10 or 20 years ahead. Photovoltaic conversion involves a much more complicated process than other devices, e.g., transistors and electroluminescent diodes, but fundamental knowledge and new materials are needed to progress in this field, which, to my sense, will become one of the major objectives in the next 20 years.

  What are the social implications of your work, if any?

Social implication is evident, and has been a constant leitmotiv of the moves I made during my scientific career. I thought at the very beginning of my work at the interface between chemistry and physics that we should be able to adapt the versatility offered by chemistry to the vast and high added value market of physics. As a matter of fact, I often use the following picture: the field of polymers (plastics, paints, etc.) came on the market in the ‘40s, and its success was mainly due to the fact that chemistry allows the fine-tuning of the mechanical, optical, thermal, chemical, etc., properties of the polymers. So the potential interest of organic-based or polymer-based devices will also rely on the fact that we should be able to tune the mechanical (flexible), optical (transparent) properties of this new class of devices. Flexible large-area, lightweight, low-cost displays will be soon on the market, as well as smart cards with increased space for memory and logic.

In the field of DNA chips, real-time reading of information is actually considered by biomedical companies as an important step.

As a social implication of my work, I would also like to add that I trained many graduate students (and post docs) in my lab to this field of materials science, which requires the understanding of both chemistry and physics. These newly formed people went out in other labs, and developed the field. For instance one of them, Jean Roncali, was initially a technician in my lab, and I convinced him to progress in research. He finally agreed, got his Ph.D., and is now well established in science in the field of conjugated polymers.

  What tools or technological advances have been important in your research, if any?

Of course, the latest techniques such as near-field microscopes are of importance, but I have to say that they have not been critical in the decision to move the research in a new specified area

  Did you expect your work to become highly cited, or is this surprising to you?

When starting a new research field, I didn’t really care for the possible citations of my future work, which had to be accomplished first. But once some steps have been achieved in your research, publication of results becomes of highest importance in order to obtain the response of the scientific community to your work. Then, once your work has been screened by the scientific community, the citation index becomes one of the most important observables of the real significance of your work, of its long-term potential on all levels, i.e., on a fundamental point of view as well as for the possible applications. So in my own case, during my experiments I have been mainly motivated by the pleasure and plenitude brought by research, by the passion to discover and pioneer new areas, by the infinite happiness of obtaining an experimental result which meets the prediction made before the experiment, by the excitement of a new finding. But a good citation record makes me very glad, of course, due to the fact that it expresses the agreement of the scientific community with the accomplished work, and recognition of the validity of my scientific moves.

In this regard, I would also like to mention that the way some results are accepted (and sometimes taken over) by companies is also a significant response to one’s work.

  How rapidly has the state of our knowledge about your field evolved in the past decade, and what were the key discoveries that furthered the advancement of the field?

This new area of organic-based devices raised a large interest, both for the understanding of materials properties in terms of molecular characteristics, and also for their large potential of applications. So, we were fortunate in that many other labs—belonging to companies such as Lucent-Bell Labs, IBM, and Philips, as well as to universities—invested very strong research efforts in this field, in all directions (theory, materials, experimentals, technology). This stream allowed decisive steps to be made in all of these directions, for the benefit of the whole area. The scientific community in universities and in companies is now at the level of prototypes of devices and of real applications (smart cards, flat panel displays, tags, and low-end electronics).

  What is your prediction for the state of our knowledge about your field 10 years from now?

There are still strong needs i) in theoretical models adapted to describe charge transport in organic materials, ii) in new materials with improved properties, iii) in technology, which explain the steady effort devoted to this field. So I am confident that improvements in all these fields will be realized in the future, and that large sectors of applications based on the actual use of amorphous-silicon (or even polycrystalline silicon) as active semiconducting layer will be replaced by organic-based semiconductors. I envision smart cards, flat and flexible (transparent?) displays, tags, low weight and flexible electronics for military applications, etc. Besides, we are just entering a new area where new mechanical, optical, and thermal properties can be designed in devices, by subtle chemical variations on the molecules involved. The a priori control of the electronic band level energies will also allow building devices possessing a large set of predetermined characteristics.

So we are in a same position as we were in the ‘40s, when polymers were launched. Who would have anticipated at that time the extraordinary development of plastics? I think we will go in the future to a "Polymer-Based Electronics à la Carte."

  Would you like to leave any other comments about your work or share a personal side of yourself?

I would just like to give one comment, which deals with my move, in 1991, towards the frontier of chemistry and biology. At that time, in 1991, we in France experienced a very sad problem linked to AIDS-infected blood, which had been given to young hemophilic people. There was a lot of concern in France about this problem, and I remember these young AIDS-infected people who were interviewed on the TV. Although knowing they were condemned to die, and although their faces were already very marked by this disease, they seemed very calm and talked about the need for better knowledge. I felt myself extremely moved by this situation, and I decided that it was my responsibility, as a scientist, to try to bring some new knowledge at the interface with biology. So over one year I went back to University and attended biology lectures, one afternoon every week. After that, I analyzed the points where I could contribute to some level, and I decided to go for the real-time recognition of DNA and antibodies, based on functionalized conjugated polymers (functionalized with oligonucleotides or antigens respectively).

And now, after having invested part-time over eight years in this completely new field for me, I think promises have become reality. I have a strong contractual relationship with the largest biomedical company in France for developing new DNA chips based on my work. A first series of prototypes is under development, papers have been published, patents have been applied, and I am often asked to give lectures on this topic. I have also written a chapter of a book published by the National Institute of Health in Bethesda, at their request. I feel very happy now to have accomplished this trip toward biology, and to have answered the vow I made to myself some nine years ago.

To sum up in a few words I would like to leave this message:

For decades, and contrary to the humanists of some centuries ago, most scientists have specialized in a very specialized area, defining themselves as experts in the tools used by chemists or physicists. Universities thus show a collection of spectroscopists (even subdivided into mass spectroscopy, IR spectroscopy, surface spectroscopy, etc.), electrochemistry, photochemistry, kinetics, modeling, low-temperature physics, etc. In my case, I have always been attracted just by new knowledge, knowledge by itself, and I have tried to learn enough physics, chemistry, and biology to allow me to explore some new fields, mostly at the frontiers between physics, chemistry, and biology. So I never defined myself as a specialist of any technique in use in these disciplines—I never wanted to—but rather as trying to answer to some challenges, whatever the experimental expertise needed.

Professor Françis Garnier
Laboratory of Molecular Materials Research
Centre National de la Recherche Scientifique