Grating and waveguide plasmonic sensors

Lead Research Organisation: Aston University
Department Name: Sch of Engineering and Applied Science


Femtosecond lasers produce pulses of light which are extremely short and at the same time extremely powerful. The intensities available when light from such a laser is focussed down are capable of modifying the structure of transparent materials or even ablating material from the surface. We have developed an understanding of the interaction of fs laser pulses with optical glasses so that, depending on the pulse parameters, we can create light waveguides, couplers, bends and grating structures or even machine the surface to alter its topology on a micron scale.

In this project we wish to bring these capabilities together to create a generic plasmonic sensing technology. Surface plasmons are oscillations of the free electrons in a thin metal film and these can be generated using the energy from light travelling in a waveguide close to the metal film. Importantly, the transfer of energy from the light to the plasmon only occurs at a well defined wavelength which depends strongly on the refractive index in a micron thick region above the metal film where the electric field of the plasmon extends. By sending a broad spectrum of light though the waveguide near the metal film and noting which wavelength is absorbed by the device it is possible to measure the refractive index above the metal very accurately.

If chemical or biochemical specific coatings are applied to the metal film then the sensor can detect specific species. In this proposal we plan to investigate the use of aptamers in this regard. Aptamers are oligonucleotide sequences, which can be designed to bind to specific molecules, proteins, DNA sequences or even cells, providing a highly flexible sensing technology.

An additional application for the technology is as a means of monitoring cell movement and growth. Cells contact a surface at specific points and if a cell is placed on the plasmon supporting metal film, light will be scattered from the plasmon field at the points of contact. This light may be viewed using a microscope which will allow the movement of the cells to be tracked over time. Cells respond differently depending on surface topology and the fs laser can be used to modify the sensor surface to enable studies of the effect of different surface topologies on cell movement and growth.

Planned Impact

We are aiming to develop a generic sensing technology applicable in many areas:

- In-line measurements in chemical plants.
Beneficiaries: industry through improved efficiency and productivity

- Remote environmental sensing and monitoring of airborne and water based pollutants.
Beneficiaries: sensor manufacturers, environment agency, the public via a more healthy environment

- Multiple tests for various chemicals on one sensor, as well as the potential for multiplexed sensing arrays.
Beneficiaries: health industry and patients through more sensitive and timely analysis of biopsies, security industry and society through sensitive and timely identification of pathogenic chemical and biochemical species.

- Improved understanding of the interactions between cells and their environment for controlling the cellular status and producing biosensor-based cell assays.
Beneficiaries: Tissue engineering including stem cell research and ultimately patients

- Cellular diagnostics; automated individual cellular diagnostics for specific proteins, enzymes, carcinogens or infections by monitoring cellular metabolism along with studies of cellular properties of normal and diseased cells.
Beneficiaries: Improved information to the health care professional leading to better outcomes for patients; pharmaceutical industry through ability to quickly assess the impacts of drugs on cells and a better understanding of drug delivery at the cellular level.

Our research will of course be disseminated through the channels of international journal publications and major international conferences. In addition we will seek out potential commercial partners to exploit the technology in specific fields (for example our project partner TQ Environmental for methane detection). The photonics research group has a more than 15 year solid track record of such collaborative activity which has resulted in several spin-off companies. We will find partners through our extensive contact list and by publicising our work in more commercially focussed environments, such as via the knowledge transfer networks (this avenue has proven productive in the past) and with the assistance of the Aston University Business Partnership Unit. Further details are provided in the Pathways to Impact document.


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Description We have developed a sensor based on an optical fibre or other waveguide that of itself provides very high sensitivity to refractive index. Importantly, the geometry of the device has allowed us to attach a variety of coating materials providing a specific response to target species. Two major demonstrations involving radically different coatings have been carried out so far.

Firstly we have shown that a coating of carbon nanotubes provides a specific detection of carbon dioxide at room temperature. This is the first utilisation of the optical properties of carbon nanotubes for this purpose and importantly opens up a range of applications as carbon nanotubes can be processed to respond to different gases.

Secondly we have used a coating of aptamers, which are short nucleic acid like molecules that can be synthesised in the laboratory to respond to a huge array of chemical and biochemical species. We have shown that our devices can detect concentrations of thrombin down to the 50 attomolar level without additional enhancement techniques and reveal real time kinetic behaviour. The selectivity of the technique has also been demonstrated using sequences of DNA.

With regard to using ultra-short pulse (fs) lasers to directly write waveguides; a significant challenge encountered was to bring the waveguide close to the surface with low loss. Several approaches were investigated of which two proved to be attractive. Firstly, in order to address high bend losses in the directly written curvilinear waveguides needed to reach the sample surface, we devised a soft-annealing process, leading to 5x smaller waveguide dimensions and 1-2 order of magnitude lower bend losses than were obtained at the project start. Secondly we have used fs machining to reveal the evanescent field of buried waveguides.
Exploitation Route The sensing approach developed in this work is very generic and can be taken forward in many areas. Our current focus is on obtaining funding to develop sensors to provide real time, remote environmental monitoring of chemical and biochemical polutants.
Sectors Aerospace, Defence and Marine,Agriculture, Food and Drink,Chemicals,Communities and Social Services/Policy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

Description CUT 
Organisation Cyprus University of Technology
Country Cyprus 
Sector Academic/University 
PI Contribution Preparation of sensor devices
Collaborator Contribution Assistance in fs machining of structures and sensor analysis
Impact "Photonic gas sensors exploiting directly the optical properties of hybrid carbon nanotube localized surface plasmon structures", Light: Science & Applications, 2016 "Highly sensitive, localized surface plasmon resonance fiber device for environmental sensing, based upon a structured bi-metal array of nano-wires", Optics Letters, Vol. 39, Issue 20, pp. 5798-5801, 2014. "Physical characteristics of localized surface plasmons resulting from nano-scale structured multi-layer thin films deposited on D-shaped optical fiber," Optics Express, Vol. 21 Issue 16, pp.18765-18776, 2013. "Formation and characterisation of ultra-sensitive surface plasmon resonance sensor based upon a nano-scale corrugated multi-layered coated D-shaped optical fibre", Jn. Quantum Electronics Vol. 48, No. 3 pp.394-405, 2012. "Localized surface plasmon fiber device coated with carbon nanotubes for the specific detection of CO2", SPIE Optics+Photonics, San Diego, USA, 2015 "An ultra-sensitive localised surface plasmon resonance fibre device for environmental sensing based upon a structured bi-metal coating", OFS23, Proc. SPIE Vol. 9157, 91574M, Santander, Spain, 2-6 June 2014. "Generation and performance of localised surface plasmons utilising nano-scale structured multi-layered thin films deposited upon D-shaped optical fiber", SPIE Optics+Photonics, Nanoengineering: Fabrication, Properties, Optics, and Devices X, San Diego, California, USA, 2013.
Start Year 2013
Description Florence 
Organisation University of Florence
Country Italy 
Sector Academic/University 
PI Contribution Designing and fabricating sensing platforms to take advantage of aptamer coating provided by collaborator
Collaborator Contribution Aptamer coating to render the devices highly selective. Specific detection of thrombin demonstrated.
Impact Paper under review
Start Year 2009
Description LHS 
Organisation Aston University
Department School of Life and Health Sciences
Country United Kingdom 
Sector Academic/University 
PI Contribution Sensor device fabrication
Collaborator Contribution Assisting with experimental procedures for biochemical sensing
Impact Paper under review
Start Year 2012
Description Lincoln 
Organisation University of Lincoln
Department National Centre for Food Manufacturing (NCFM)
Country United Kingdom 
Sector Academic/University 
PI Contribution Designing sensor for possible farming and agriculture applications
Collaborator Contribution Planning of experiments aimed to support future grant proposal
Impact Still at the point of discussing experiments
Start Year 2015
Description Nottingham Molecular Imprinting 
Organisation University of Nottingham
Department Department of Electrical and Electronic Engineering
Country United Kingdom 
Sector Academic/University 
PI Contribution Designing and fabricating sensing platforms to take advantage of molecular imprinting coating provided by collaborator
Collaborator Contribution Coating our sensor platform with molecular imprinting medium
Impact Experiments currently in progress
Start Year 2014