Title: Using Self-Assembling Swimming Devices to Control Motion at the Nanoscale
Funder: Engineering and Physical Sciences Research Council

Abstract: 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.


Research activity codes: 4.1 DISCOVERY AND PRECLINICAL TESTING OF MARKERS AND TECHNOLOGIES;5.1 PHARMACEUTICALS
Health categories: GENERIC HEALTH RELEVANCE