Dielectrophersis Control of InAs based Nanowires for bio sensing

Lead Research Organisation: University of Liverpool
Department Name: Electrical Engineering and Electronics

Abstract

Semiconductor devices are increasingly being utilized in healthcare based sensor applications due their excellent ability to detect minute changes in their surroundings due via alterations in their electrical and optical properties. Recently there has been much interest in semiconductor nanowires, these wires are grown vertically upwards from a semiconductor surface, with nanowires having been demonstrated from a range of compound semiconductors including, Gallium Arsenide, Gallium Phosphide, Indium Arsenide and Indium Antimony. Growth of these wires is initiated either by initially depositing tiny metal droplets on the surface or by forming nanoscale holes in an oxide mask. The resultant nanowires can have lengths in excess of 1um and diameters below 100nm.

These nanowires are of particular interest for bio-sensing and healthcare applications for a number of reasons, firstly their small size makes them ideal to integrate molecules and other optical and electrical components. Secondly due to the cylindrical shape of the wires the majority of the charge resides on the surface making them especially sensitive to changes in their environment, for example arising from the presence of differing bio-markers.
However the vertical nature of the growth and resultant device geometry severely limits the exploitation of these nanowires as the nanowires are routinely planarised and encapsulated under a polymer layer. This results in a relatively large final device and also supresses much of the surface charge.

The proposed work here offers a step-change in the development of nanowire based sensors and devices by utilizing the process of dielectrophoresis. This is a process whereby the application of a non-uniform electric field results in a force upon a charged particle. By appropriately controlling the electric field it is possible to utilize this process to accurately move and position particles. To achieve this the nanowires will be removed from their native growth substrate and then dispersed in solvent before undergoing dielectrophoresis to position the wires at pre determined positions. This offers an attractive route to undertake nanowire bio-sensing and monitoring due to the ability to integrate the nanowires directly with microfluidics and other optical or electrical systems thus exploiting the accurate and reliable positioning offered by this technique.

A further advantage is that nanowire devices formed via this technique can be achieved in a horizontal rather than vertical configuration. This will make integration with other components much more straightforward and also enable the whole surface of the nanowire to interact with its environment, greatly enhancing the sensitivity of the wires to any changes in their environment. These potential benefits offer the possibility to greatly enhance the performance of nanowire based sensors and devices as well as enabling to be fabricated more efficiently and at a reduced cost.

Specifically this project aims to fabricate nanowire devices via dielectrophoresis, establishing relationships between the process parameters and the final devices electrical, optical and physical characteristics, opening a route for predictable device fabrication. Finally nanowire devices will be integrated with microfluidic systems to demonstrate an ionic flow sensor, allowing both the concentration and flow rate of liquids to be monitored in a compact lab on a chip device.

Planned Impact

The semiconductor photonics industry is a critical area of the UK and EU economy which is estimated to reach over 600 billion Euros by 2020 and currently employs over 300,000 people directly, with a total impact of around 30 million jobs (figures for the EU). The EU has a number of world leading companies with global market share in some areas as high as 40%. Photonics is at the heart of solutions for a number of key societal challenges including healthcare, digital security, energy generation, energy efficiency, and climate change. Maintaining the competitiveness of the UK and EU semiconductor industry requires the continuous development of new materials, structures and devices with much of the fundamental research occurring in universities. Exemplary immediate impacts that we aim to generate include:

Training: There is an urgent need to train over 100,000 engineers and scientists each year to power the UK economy. This project provides ideal career development opportunities for the PDRAs and the students. The benefits will include enhancing their research methodologies, PhD completion for the students and communication of results at international conferences and appropriate high impact international journals. A number of students pursuing Bachelor and Master degrees will also benefit directly from this project by working on smaller scale research projects.

Economic: The worldwide semiconductor market was worth $335 billion in 2015 and is expected to grow to $390 billion by 2019. Semiconductor sensors currently account for $9 billion of the market and is expected to be one of the strongest growing sectors of the market over the coming years with growth predictions of around 4% per annum over this time frame. Similarly bio sensors is a rapid growing market with a large number of major companies investing in and developing new technologies especially for rapid diagnosis and point of care health based applications (for example Philips Healthcare, Roche, and Abbott). The applicant has undertaken some initial discussions with these companies to begin to raise interest and awareness of the potential of III-V nanowire based devices for bio sensors. To further develop and formalize these discussions it is intended to organize and hold a workshop towards the end of the project to fully disseminate the results and facilitate discussions to further commercialize and exploit the research.

Societal: The long term aims of this proposal have the potential to realize a new generation of biological and medical sensors that can be utilized in low cost, compact and highly efficient lab-on-a-chip systems for rapid and remote diagnosis. The research developed through this proposal will also have the potential to influence a range of other fields through the development of new semiconductor devices, for example telecommunications, defence and environmental monitoring. As such the results generated will be of direct benefit to developing a healthy, resilient and connected nation and therefore industry, government and the public will all have a strong interest in the work. The Semiconductor group at Liverpool has a number of formal and informal collaborations with major research institutions worldwide, the university also has extensive expertise in the health sciences and the associated development of biosensors, again with well-established partnerships with research groups worldwide and NHS institutions. The applicant intends to utilize these networks and contacts to enable interaction and dialogue with interested parties and to develop new collaborations. The University of Liverpool has also recently launched a new research to business incubator named Sensor City, which will provide a hub for small and medium sized companies to interact with university research in the area of sensor technologies.
 
Description The principle of dielectrophoresis can be utilized to control and accurately position semiconductor nanowires, formed from a range of compound semiconductor alloys. The dielectrophoresis process is influenced by the semiconductor alloy and the medium that the nanowires are dispersed in, a key requirement is to ensure the nanowires do not cluster within the dispersion liquid. This can be avoided by selecting dispersing mediums with appropriate electrical charge. This work and project are still ongoing (project has not yet ended). The results from this have been used to demonstrate the potential to use NW based devices as a low cost rapid detection method for COVID-19
Exploitation Route The dielectrophersis process is relativley simple to undertake so others can utilize these findings to fabricate nanowire based devices for a range of end electrical and photonic applications.
The results from this have been used to demonstrate the potential to use NW based devices as a low cost rapid detection method for COVID-19
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Electronics,Healthcare

 
Description Cardiff University 
Organisation Cardiff University
Country United Kingdom 
Sector Academic/University 
PI Contribution Development of GaN Nanowire and nanostructured bio and gas sensors. Device functionalisation and characterisation
Collaborator Contribution Development of GaN nanostructures, and the epitixal growth of them
Impact na
Start Year 2020
 
Description Fraunhofer 
Organisation Fraunhofer Society
Department Fraunhofer Institute for Applied Optics and Precision Engineering
Country Germany 
Sector Academic/University 
PI Contribution Additional measurements and simulations on new materials
Collaborator Contribution New materials to work with
Impact Too early in partnership
Start Year 2019
 
Description National Tsing Hua University 
Organisation National Tsing Hua University (Taiwan)
Country Taiwan, Province of China 
Sector Academic/University 
PI Contribution Have been sent novel NW samples by National Tsing Hua University for analysis and device fabrication. Have performed Electron Micrscope Analysis of Samples and undertaken device fabrication using DEP. Currently analysing results with publication and potential proposal expected as outcomes.
Collaborator Contribution Have been sent novel NW samples by National Tsing Hua University for analysis and device fabrication.
Impact None Yet. But publications expected this year
Start Year 2021
 
Description Pint of Science Talk and Demo 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Pint of Science, talk discussing applications of nanowire based bio sensors
Year(s) Of Engagement Activity 2019
URL https://news.liverpool.ac.uk/2019/04/08/grab-a-pint-of-science-with-liverpool-researchers/
 
Description School Visit Liverpool 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact A talk to GCSE science pupils (approx. 150) about the research and possible impacts, followed by Q and A
Year(s) Of Engagement Activity 2018
 
Description Skype a Scientist Event 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Schools
Results and Impact A series of skype talks to school children and the general public about my research and more generally about being a scientist/engineer. Largely under a Q and A format with intention of widening diversity in the field.
Year(s) Of Engagement Activity 2017,2018
 
Description Talk at education confrence for science teachers 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact A talk outlining the research aims, objectives and findings from this project to a group of science teachers at an annual education conference. There was discussion afterwards and several invitations to come into schools to talk directly with pupils on the research and its potential impact.
Year(s) Of Engagement Activity 2017