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

Lead Research Organisation: University of Sheffield
Department Name: Chemical & Biological Engineering

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.

Planned Impact

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.

Publications

10 25 50

publication icon
Archer RJ (2018) A Pickering Emulsion Route to Swimming Active Janus Colloids. in Advanced science (Weinheim, Baden-Wurttemberg, Germany)

publication icon
Campbell A (2016) Preparation and 3D Tracking of Catalytic Swimming Devices. in Journal of visualized experiments : JoVE

publication icon
Campbell AI (2013) Gravitaxis in spherical Janus swimming devices. in Langmuir : the ACS journal of surfaces and colloids

publication icon
Das S (2015) Boundaries can steer active Janus spheres. in Nature communications

publication icon
Dunderdale G (2015) Directed Propulsion, Chemotaxis and Clustering in Propelled Microparticles in Current Physical Chemistry

publication icon
Ebbens S (2012) A fantastic voyage? in Materials Today

 
Description 1. A much deeper understanding of methods to control small scale autonomous swimming devices
2. Insights into swimming device mechanism
3. New limitations that a certain category of device will face for future applications
4. A new method to produce devices that can overcome the limitations found in (3)
Exploitation Route Findings can be used in the future to develop new faster medical diagnostic tools. Findings have informed the theoretical and experimental communities within the field of the award. Findings also have the chance to enable a new form of microfluidics that can have significant future impact in many disciplines.
Sectors Pharmaceuticals and Medical Biotechnology

URL http://steve-ebbens.staff.shef.ac.uk/
 
Description EPSRC Healthcare Technologies Impact Fellowship
Amount £483,709 (GBP)
Funding ID EP/N033736/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 11/2016 
End 11/2018
 
Description Researcher Mobility Program
Amount £2,040 (GBP)
Organisation Worldwide Universities Network 
Sector Academic/University
Country Global
Start 03/2014 
End 04/2014
 
Description Boundary Steering 
Organisation Penn State University
Department Department of Chemistry
Country United States 
Sector Academic/University 
PI Contribution Provided experimental data showing the phenomena of boundary steering in Janus swimmers
Collaborator Contribution Provided access to lithographic facilities to make patterned substrates to further demonstrate the phenomena. Performed zeta potential experiments to ascertain the role of electrostatic interactions in the phenomenons mechanism.
Impact DOI:10.1038/ncomms9999 Disciplines: Engineering and Chemstry
Start Year 2014
 
Description Ensemble simulation 
Organisation Robert Gordon University
Country United Kingdom 
Sector Academic/University 
PI Contribution Brought a potential simulation scenario to the attention of an interested researcher, and shared experimental data to inform model development
Collaborator Contribution Ran simulations for an ensemble of swimming devices that are currently hard to perform experiments for
Impact Synthetic running and tumbling: an autonomous navigation strategy for catalytic nanoswimmers Stephen J. Ebbens, Gavin A. Buxton, Alexander Alexeev, Alireza Sadeghi and Jonathan R. Howse SOFT MATTER Volume: 8 Issue: 11 Pages: 3077-3082 DOI: 10.1039/c2sm07283a Published: 2012
Start Year 2011
 
Description Mechanistic Janus Swimmer Research 
Organisation University of Oxford
Department Department of Physics
Country United Kingdom 
Sector Academic/University 
PI Contribution Provided a wide range of experimental data to inform theoretical and mechanistic insights
Collaborator Contribution Theoretical analysis of our results and guidance on future research directions
Impact A series of joint papers: Size dependence of the propulsion velocity for catalytic Janus-sphere swimmers Stephen Ebbens Mei-Hsien Tu,Jonathan R. Howse, and Ramin Golestanian Phys. Rev. E 85, 020401(R) (2012) Electrokinetic effects in catalytic platinum-insulator Janus swimmers. Ebbens, S. J., Gregory, D. A., Dunderdale, G., Howse, J. R., Ibrahim, Y., Liverpool, T. B., & Golestanian, R. European Physical Letters, 106(5), 58003 2014 Boundaries can steer active Janus spheres Das, S., Garg, A., Campbell, A. I., Howse, J. R., Sen, A., Velegol, D, Golestaninan, R, Ebbens, S. J. NATURE COMMUNICATIONS Volume 6 Article Number 8999 DOI:10.1038/ncomms9999 Published 2nd December 2015
Start Year 2009
 
Title Image Analysis Software 
Description Software that can analyse videos to determine properties of objects moving within fluids. 
Type Of Technology Software 
Year Produced 2014 
Impact Acknowledged use in other publications e.g: Micromotors Powered by Enzyme Catalysis Krishna Kanti Dey, Xi Zhao, Benjamin M. Tansi, Wilfredo J. Méndez- Ortiz, Ubaldo M. Córdova-Figueroa, Ramin Golestanian, and Ayusman Sen Nano Lett., Just Accepted Manuscript • DOI: 10.1021/acs.nanolett.5b03935 • Publication Date (Web): 20 Nov 2015 
 
Description Interview with BBC world service 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Gave interview to BBC world service news hour program about a new method to steer swimming devices
Year(s) Of Engagement Activity 2015
 
Description Talk at Sheffield Festival of Science and Engineering 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact 60 members of the general public attended a lecture. Several questions followed which indicated a high level of engagement in the audience
Year(s) Of Engagement Activity 2015