Using Self-Assembling Swimming Devices to Control Motion at the Nanoscale

Films such as the "Fantastic Voyage" imaginatively explore the idea of developing miniaturised devices capable of navigating through the body and performing tasks, such as removing tumours. While this vision may seem fantastical, the reality is that researchers are moving closer towards this goal. At present, man-made machines a fraction of the width of a human hair can swim around in water containing a small amount of chemical "fuel" without any external intervention. By equipping these devices with magnets, they can also be manually steered towards cargo using external fields, which they can pick up, drag and then release. However these achievements have not yet enabled the ultimate goal of making devices that can navigate themselves through the body to deliver a drug to a particular therapeutic target. In this case it is impractical to use external steering, and the devices must instead find their own way. This is very challenging because of the way in which liquid environments are experienced by miniaturised devices. Due to the way in which liquid properties change at small sizes, the devices experience the surrounding fluid as treacle like; meaning they cannot generate motion using the swimming motions that we are familiar with. Also the devices are constantly jostled by collisions from surrounding molecules, causing them to change their position and orientation randomly, and in some parts of the body there are turbulent flows to contend with.

The aim of this Fellowship is to overcome these challenges to build miniaturised swimming devices that can direct themselves towards targets without external intervention, to enable a range of applications including targeted drug delivery. In order for this to be possible the devices must be able to adjust their motion according to their surroundings. This will be achieved using a new range of materials that expand and contract according to the presence or absence of certain signalling chemicals. These size changes will cause the swimming device to change the degree to which it is affected by the random knocks it receives, either keeping it moving in a straight line, or encouraging it to change direction rapidly. The size changes will and also alter the speed of the device. In this way devices can exploit the chaos of their surroundings to carry them to specific locations. The ability to attach and release cargo in a similarly responsive way will also be developed. As well as producing significant advances for drug delivery, the transport systems developed by the Fellowship will also be used to transport material for analysis within medical diagnostic devices. In addition, a class of swimmers that rotate rather than translate will be made and used to mix fluids such as chemical reagents in the small channels of these diagnostic systems. The enhanced motion of the swimmers can also be used to speed up reaction rates in chemical processes, resulting in faster industrial processes.

To build swimming devices for the above tasks with desirable properties such as being fast, and moving in a straight line, the Fellowship will develop new manufacturing methods. Combining conventional parts together to make devices can simply be carried out by positioning them in the correct places and sticking them together, however at small scales such operations are impractically laborious and require expensive microscopic manipulations. A more practical approach is to instead equip the individual components with "sticky tags" or other features that will bias the self-assembly to make preferred structures. However some variations will remain. One of the key novel methodologies of the work will actually exploit this variation, by applying "natural selection" using a physical obstacle course to pick out devices with the best performance for a particular task. In this way efficient swimmers can assemble themselves by exploiting a random process without requiring external intervention.

Society: The Fellowship can provide significant advances in health care, by enabling a potentially transformative method for targeted drug delivery, and improving the function of medical diagnosis devices. The new transport systems for drug delivery that will be developed can reduce side effects and minimise the amount of active ingredient required, reducing the cost of medicines. The devices will also improve the speed of fluid mixing and analyte transport in micro fluidic devices for medical diagnosis. These healthcare applications were recently identified as top priorities for applied Nanoscience and Technology research (2009 "Nanoscience through engineering" theme day RCUK report), and the importance of developing this technologically inspired strategy to address the societal issues of living with an ageing and growing population was recognised in the 2009-2012 Nanoscale Technologies Strategy document.

The superdiffusive catalysts that will be produced by the Fellowship can also benefit society by improving the efficiency of catalytic reactions, reducing the price of goods and having environmental benefits.

The Fellowship will also inspire and contribute to the education of school children and promote public awareness of Science, encouraging debate about the perceptions of Nanotechnology. The Fellowship will produce miniaturised devices that can self-assemble, swim rapidly, change size and pick-up and release cargo. The immediate visual impact of this behaviour will be used as the basis for educational material, for a range of age groups, with goals ranging from introducing the basic concept of scale, to demonstrating phenomena such as viscosity and inertia. Comparison with science fiction film portrayals of miniaturised devices will also be employed to encourage an imaginative engagement with the Fellowship.

To engage the general public, the societal benefits achievable by the technology developed in the Fellowship for applications such as drug delivery and medical diagnosis will be highlighted. In this way the Fellowship will contribute to improving the public perception of nanotechnology, and provide a forum for debate about the public acceptance issues associated with nanoscale technologies that come in intimate contact with the user. The importance of addressing these issues was outlined in the 2006 ERSC report "The Social and Economic Challenges of Nanotechnology" which highlights how public Nanotechnology perception has been damaged by Dystopian view-points expounded by high profile public figures.

Economy: The Fellowship has potential economic impact leading to wealth generation, including, R+D investment, generation of intellectual property and the creation of companies. As described above, the Fellowship will deliver autonomous transport systems to potentially transform drug delivery and solve fluidic device transport challenges used for medical diagnosis. The potential for UK wealth generation in this sector is illustrated by the predicted market revenue rise in the area of Nanoparticulate drug delivery over the time scale of the fellowship: from $75 M (2007) to $ 2650 M by 2015. Economic benefits will be delivered to existing UK SMEs in the healthcare sector that have a timely demand for the transport systems that will be developed in this Fellowship. Targeted drug delivery using the Fellowships technology will also be highly attractive to large Pharmaceutical companies. IP to protect these ideas will also deliver economic benefits to the host University, and further benefits can be delivered by the instigation of start-up companies as part of the commercialisation process. In the chemical industry the rate of currently diffusion limited reactions will also be improved with the potential to produce economic benefits by increased manufacturing speeds.