Research in nanotechnology is anticipated to lead to the development of novel devices and systems with applications in multiple areas including materials, energy, defense, aerospace, and medicine (Lux Research 2007
; NSET 2007
). However, while some early nanotechnology-enabled products are already on the market, there is uncertainty about the trajectories and timing of more advanced phases of nanotechnology commercialization and also about the societal impacts and risks posed by potential nanotechnology applications (Royal Society 2004
; Wilsdon 2004
; Bennett and Sarewitz 2006
; Besley et al. 2008
). Efforts to inform discourse about the development pathways of nanotechnology and their societal impacts require an engagement with the technical content of nanotechnology. This paper contributes to this discourse by examining the extent to which nanotechnology research is increasing its focus on “active nanostructures.”
The concept of “active nanostructures” was put forward by Dr. Mihail Roco (2004
) in his vision of four generations of nanotechnology. This vision defined successive stages in a timeline for nanotechnology prototyping and commercialization, beginning with current first generation passive products (such as nanocoatings, nanoparticles, or nanostructured materials). In Roco’s conception, active nanostructures form the basis of the second generation of nanotechnology development beginning around the mid-2000s. As described by Roco in a workshop for the International Risk Governance Council (IRGC), active nanostructures have characteristics such that their “…structure, state and/or properties change during their use; successive changes may occur either intended or unforeseen reactions in the external environment” (IRGC 2007
). According to Roco, this evolving functionality may be reversible or irreversible. Targeted drugs, actuators, and adaptive structures were among the examples of applications of active nanostructures. Roco envisaged two further stages of nanotechnology evolution—systems of nanosystems and molecular nanosystems—on a trajectory of development leading through to the 2020s. In this article, we concentrate on exploring the first shift in this model—the transition from passive to active nanostructures. To the extent that this shift is underway, it could signify an important inflexion in the development of nanotechnology, since impacts (including benefits as well as potential risks) may be both greater and different in character in the second phase when compared with the first. The International Risk Governance Council has characterized passive and active nanostructures as possessing distinct risk “frames”, in which the risks associated with active nanostructures challenge current risk assessment paradigms and are associated with “system uncertainties” (IRGC 2007
). We do not make any additional judgments in this article about these impacts, risks, and implications. Rather, our concern is with the fundamental and critical issue of how to measure whether there is indeed a shift to active nanostructures.
The US National Science Foundation (NSF) (where Dr. Roco is Senior Advisor for Nanotechnology) has been soliciting proposals for “Active Nanostructures and Nanosystems” (ANN) since 2005. The NSF’s grant solicitation defines an active nanostructure thus: “An active nanostructure changes or evolves its state during its operation.” The NSF’s Nanoscale Interdisciplinary Research Team (NIRT) grant gives the following examples of active nanostructures: nanoelectromechanical systems (NEMS), nanomachines, self-healing materials, nanobiodevices, transistors, amplifiers, targeted drugs and chemicals, actuators, molecular machines, light-driven molecular motors, plasmonics, nanoscale fluidics, laser-emitting devices, adaptive nanostructures, energy storage devices, and sensors (National Science Foundation 2006
Another definition of active nanostructures is offered by James Tour, an organic chemist. Based on research in his laboratory at Rice University, he offers a classification of nanotechnology based on whether the role of the nanoscale entity in a prototype involves passive, active, or hybrid nanotechnology. In the case of active nanotechnology, “… the nano entity does something elaborate such as absorbing a photon and releasing an electron, thereby driving a device, or moving in a specific and definable fashion across a surface” (Tour 2007
). The definitions offered by Roco and Tour overlap to a large extent, except that Tour does not include nanostructures with irreversible evolving functionality. These overlapping conceptions of active nanostructures are also discussed in a report by the Project on Emerging Nanotechnologies (Davies 2009
In the following article, we present analytical methods and results from our ongoing research on the trajectories of active nanostructures. Our aim is to inform nanotechnology dialogue and governance by providing robust approaches to measuring significant shifts in nanotechnology research and applications. We address two research questions in this paper: (a) Is there a shift to active nanostructures? (b) How can we characterize the prototypical areas into which active nanostructures may emerge?