7 research outputs found
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Effect of carbon nanotube alignment on nanocomposite sensing performance
Abstract
The objective of this study is to derive a numerical model of carbon nanotube (CNT)-based thin films that accurately reflect their electrical and electromechanical performance as observed through experimental tests. Although nanocomposites based on CNTs dispersed in polymer matrices have been studied extensively, their nanocomposite properties vary depending on CNT orientations. This study aimed to explain how differences in nanocomposite behavior could be revealed by numerical models considering different CNT alignment conditions. First, a percolation-based thin film model was generated by randomly dispersing CNT elements in a predefined two-dimensional domain. The degree of CNT alignment in the film was controlled by limiting the CNT elementsโ maximum angle they make with respect to the filmโs longitudinal axis. Then, numerical simulations on CNT-based film models were conducted. Second, multi-walled carbon nanotube (MWCNT)-epoxy films were prepared via drop casting. Alternating current was applied to the MWCNT-epoxy mixture before curing to prepare films with different degrees of CNT alignment. The electrical and electromechanical properties of these specimens were characterized, and the results were compared with simulations. Good agreement between experiments and simulations was observed
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Nanofabrication via directed assembly: a computational study of dynamics, design & limits
Three early-stage techniques, for the fabrication of metallic nanostructures, creation of controlled topography in polymer films and precise deposition of nanowires are studied. Mathematical models and computational simulations clarify how interplay of multiple physical processes drives dynamics, provide a rational approach to selecting process parameters targeting specific structures efficiently and identify limits of throughput and resolution for each technique.
A topographically patterned membrane resting on a film of nanoparticles suspended in a solvent promotes non-uniform evaporation, driving convection which accumulates particles in regions where the template is thin. Left behind is a deposit of particles the dimensions of which can be controlled through template thickness and topography as well as film thickness and concentration. Particle distribution is shown to be a competition between convection and diffusion represented by the Peclet number. Analytical models yield predictive expressions for bounds within which deposit dimensions and drying time lie. Ambient evaporation is shown to drive convection strong enough to accumulate particles 10 nm in diameter. Features up to 1 ยตm high with 10 nm residual layers can be deposited in < 3 minutes, making this a promising approach for continuous, single-step deposition of metallic nanostructures on flexible substrates.
Selective exposure of a polystyrene film to UV radiation has been shown to result in non-uniform surface energy which drives convection on thermal annealing, forming topography. Film dynamics are shown to be a product of interplay between Marangoni convection, capillary dissipation and diffusion. At short times, secondary peaks form at double the pattern density of the mask, while at long times pattern periodicity follows the mask. Increased temperature, larger surface tension differentials and thick films result in faster dynamics and larger features.
Electric fields in conjunction with fluid flow can be used to position semi-conducting nanowires or nanotubes at precise locations on a substrate. Nanowires are captured successfully if they arrive within a region next to the substrate where dielectrophoresis dominates hydrodynamics. Successful assembly is predicated upon a favorable balance of hydrodynamics, dielectrophoresis and diffusion, represented by two dimensionless groups. Nanowires down to 20 nm in length can be assembled successfully.Chemical Engineerin
Electric Field Guided Assembly of One-Dimensional Nanostructures for High Performance Sensors
Various nanowire or nanotube-based devices have been demonstrated to fulfill the anticipated future demands on sensors. To fabricate such devices, electric field-based methods have demonstrated a great potential to integrate one-dimensional nanostructures into various forms. This review paper discusses theoretical and experimental aspects of the working principles, the assembled structures, and the unique functions associated with electric field-based assembly. The challenges and opportunities of the assembly methods are addressed in conjunction with future directions toward high performance sensors
Retinal Neural Stimulation Method Using Silicon Nanowire-based Photodetection Circuits for the Realization of High Resolution Retinal Prosthesis
ํ์๋
ผ๋ฌธ (๋ฐ์ฌ)-- ์์ธ๋ํ๊ต ๋ํ์ : ์ ๊ธฐยท์ปดํจํฐ๊ณตํ๋ถ, 2015. 8. ์กฐ๋์ผ.์ธ๊ฐ์ ๋์ ๋ค์ด์จ ๋น ์ ๋ณด๋ ๋ง๋ง์์ ์ ๊ธฐ์ ํธ๋ก ๋ณํ๋์ด ์์ ๊ฒฝ์ ํตํด ๋๋ก ์ ๋ฌ๋์ด ์์์ ์ธ์ํ๊ฒ ๋๋ค. ๊ทธ๋ฌ๋ ์์ธํฌ๊ฐ ์์๋ ๊ฒฝ์ฐ์๋ ๋ค๋ฅธ ์ ๊ฒฝ์ธํฌ๋ค์ ๊ธฐ๋ฅ์ด ๋จ์์๋๋ผ๋ ๋น์ ์ธ์งํ ์ ์์ด ๊ฒฐ๊ตญ ๋ณผ ์ ์๊ฒ ๋๋ค. ์ธ๊ณต ๋ง๋ง ์์คํ
(retinal prosthetic system)์ ์ด๋ฌํ ๋ง๋ง ์์์ผ๋ก ์ธํด ์๊ฐ ์ฅ์ ๋ฅผ ๊ฒช๊ณ ์๋ ์ฅ์ ์ธ์ ์๋ ฅ ํ๋ณต์ ์ํด ๋ง๋ง ์ธํฌ ๋ด์ ์ธ์์ ์ผ๋ก ๋ฏธ์ธ ์ ๊ทน ์ด๋ ์ด(micro electrode array, MEA)๊ฐ ์ง์ ๋ ๋ง๋ง ์๊ทน๊ธฐ๋ฅผ ์ด์ํ๊ณ ์ฌ๊ธฐ์ ์ ๊ธฐ ์๊ทน ์ ํธ๋ฅผ ์ธ๊ฐํ์ฌ ๋ง๋ง ์ธํฌ์ ์ธ์์ ์ธ ์ ๊ธฐ ์๊ทน์ ์ ๋ฐ์ํด์ผ๋ก์จ ๋ง๋ง ์์ธํฌ ์์์ผ๋ก ์๋ ฅ์ ์์ ์ฌ๋์๊ฒ ์์์ ์ธ์ํ ์ ์๋๋ก ํด์ฃผ๋ ์ฅ์น์ด๋ค.
๋ณธ ๋
ผ๋ฌธ์์๋ ์์์ธ์์ ์ํ ๊ด ๊ฒ์ถ๊ธฐ๊ฐ ๋ด์ฅ๋ ์์ ํ ์๊ตฌ ์ด์ํ์ ๊ณ ํด์๋ ์ธ๊ณต ๋ง๋ง ์์คํ
๊ตฌํ์ ์ํด ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ธฐ๋ฐ์ ๊ด ๊ฒ์ถ ๋ฐ ์๊ทน ์ ํธ ๋ณ์กฐํ๋ก์ ๋ฏธ์ธ ์ ๊ทน ์ด๋ ์ด๊ฐ ์ง์ ๋ ๊ณ ํด์๋ ๋ง๋ง ์๊ทน๊ธฐ์ ๊ด ๊ฒ์ถ ๊ธฐ๋ฐ์ ๋ง๋ง ์ ๊ฒฝ ์๊ทน ๊ธฐ๋ฒ์ ์ ์ํ๋ค. ์ ์ํ๋ ๋ง๋ง ์๊ทน๊ธฐ๋ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ธฐ๋ฐ์ ๊ด ๊ฒ์ถ ๋ฐ ์๊ทน ์ ํธ ๋ณ์กฐํ๋ก์ ๋ฏธ์ธ ์ ๊ทน ์ด๋ ์ด๊ฐ NรN matrix ํํ๋ก ์ง์ ๋์ด ์์ผ๋ฉฐ, ๋ง๋ง ์ธํฌ์ ์ด์์ด ์ฉ์ดํ๋๋ก ์ ์ฐํ ํํ๋ก ์ ์๋๋ค. ๊ฐ ํฝ์
์๋ 1๊ฐ์ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ด ๊ฒ์ถ๊ธฐ์ 2๊ฐ์ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด FET(field effect transistor)๋ก ๊ตฌ์ฑ๋๋ ๊ด ๊ฒ์ถ ๋ฐ ์๊ทน ์ ํธ ๋ณ์กฐ ํ๋ก๋ฅผ ๋ด์ฅํ๊ณ ์์ผ๋ฉฐ, ์ ํธ์ฒ๋ฆฌ ์นฉ์์ ์์ฑ๋ ํ์ค ํํ์ ๊ธฐ์ค ์๊ทน ์ ํธ(reference stimulation signal)๊ฐ ๊ฐ ํฝ์
์ ์ ๋ฌ๋๊ณ , ๊ฐ ํฝ์
์์๋ ๊ธฐ์ค ์๊ทน ์ ํธ๋ฅผ ๋น์ ์ธ๊ธฐ์ ๋น๋กํ๋ ์งํญ์ ๊ฐ์ง๋ ์๊ทน ์ ํธ๋ก ๋ณ์กฐํ์ฌ ๋ฏธ์ธ ์ ๊ทน์ ์ ๋ฌํ์ฌ ๋ง๋ง ์ ๊ฒฝ์ ์๊ทนํ๋ค.
์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ธฐ๋ฐ์ ๊ด ๊ฒ์ถ ๋ฐ ์๊ทน ์ ํธ ๋ณ์กฐ ํ๋ก๋ฅผ ๊ตฌ์ฑํ๋ ์ ์ ๋ถ๋ฐฐ๊ธฐ ๋ฐ ์ ๋ฅ ๊ตฌ๋๊ธฐ ํ๋ก๋ฅผ ์ ์ํ๊ธฐ ์ํ ๊ธฐ๋ณธ ์์๋ก์ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ด ๊ฒ์ถ๊ธฐ์ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด FET, ๊ทธ๋ฆฌ๊ณ ๋ฏธ์ธ ์ ๊ทน์ ์ ์ํ์ฌ ํน์ฑ์ ํ๊ฐํ์๋ค. ์ ์๋ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ด ๊ฒ์ถ๊ธฐ๋ ๋น์ ๋ํ ๊ฐ๋๊ฐ ์ต๋ 1,936์ ์ด๋ฅด๊ณ , ์๋ต๋์ ๊ฒฝ์ฐ 400 nm ~ 800 nm์ ํ์ฅ ๋ฒ์์์ 104 ~ 105 A/W์ ์ด๋ฅผ ์ ๋๋ก ๋งค์ฐ ์ฐ์ํ ๊ดํ์ ์ฑ๋ฅ์ ๋ณด์๋ค. ๊ทธ๋ฆฌ๊ณ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด FET๋ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด์ ๊ฐ์, ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด์ ๊ธธ์ด, ๊ทธ๋ฆฌ๊ณ FET ๊ตฌ๋ ์ ์์ ์ค๊ณ ํ๋ผ๋ฏธํฐ๋ก ํ์ฌ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด FET์ ํน์ฑ์ ์กฐ์ฌํ์์ผ๋ฉฐ, 103 ์ด์์ on-off ratio์ 5 V ๊ตฌ๋์ ์์์ ์ต๋ 225 ฮผA์ ์ ๋ฅ ๋ ๋ฒจ์ ๋ณด์๋ค. ๊ณ ๋ฐ๋ํ์ ๋ฐ๋ฅธ ์ ๊ทน์ ์ํํ์๋ ๋ถ๊ตฌํ๊ณ ์ถฉ๋ถํ ์ ๋ฅ ์ฃผ์
์ฉ๋์ ํ๋ณดํ๊ธฐ ์ํ ๋ฐฉ๋ฒ์ผ๋ก ์ํตํ์ Au ์ ๊ทน์ ํ๋ฉด์ ์ ์ฃผ๋๊ธ๊ณต์ ์ผ๋ก 5,000 โซ ๋๊ป์ nano-porousํ Pt-black์ธต์ ํ์ฑํจ์ผ๋ก์จ ๋์ ํ๋ฉด์ ์ ๊ฐ์ง ๊ณ ๋ฐ๋ ๋ฏธ์ธ ์ ๊ทน ์ ์์ด ๊ฐ๋ฅํ ๋๋
ธ 3D ๋ฏธ์ธ ์ ๊ทน์ ์ ์ํ์๋ค.
์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ด ๊ฒ์ถ๊ธฐ์ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด FET ์์๋ฅผ ์ ์ํ์ฌ ๋ง๋ง ์๊ทน๊ธฐ์ ์ ์ ๋ถ๋ฐฐ๊ธฐ ๋ฐ ์ ๋ฅ ๊ตฌ๋๊ธฐ ํ๋ก๋ฅผ ๊ตฌ์ฑํ๊ณ ๊ฐ๊ฐ์ ํ๋ก์ ๋์์ ์กฐ์ฌํจ์ผ๋ก์จ ๋ณธ ๋
ผ๋ฌธ์์ ์ ์ํ๋ ๊ด ๊ฒ์ถ ๋ฐ ์๊ทน ์ ํธ ๋ณ์กฐ์ ์๋ฆฌ๊ฐ ์ ์ ์ฉ๋จ์ ํ์ธํ์๋ค. ์ ์ํ๋ ๋ง๋ง ์๊ทน๊ธฐ์ ๊ณ ํด์๋ ๋ง๋ง ์์คํ
์ผ๋ก์ ์ ์ฉ ๊ฐ๋ฅ์ฑ ๊ฒํ ๋ฅผ ์ํด 32ร32์ ๊ณ ํด์๋ ๋ง๋ง ์๊ทน๊ธฐ๋ฅผ ์ค๊ณ, ์ ์ํ์๋ค. ์ ์๋ ๋ง๋ง ์๊ทน๊ธฐ์๋ ์ฝ 40 ฮผm ๋๊ป์ ๋งค์ฐ ์์ flexibleํ ํด๋ฆฌ์ด๋ฏธ๋ ํ๋ฆ ๋ด์ ๋จ์ ํฝ์
์ ํฌ๊ธฐ๊ฐ 110 ฮผm ร 110 ฮผm์ธ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ธฐ๋ฐ์ ๊ด ๊ฒ์ถ ๋ฐ ์๊ทน ์ ํธ ๋ณ์กฐ ํ๋ก๊ฐ ์ง์ ๋์๋ค.
์ ์ํ๋ ๋ง๋ง ์๊ทน๊ธฐ ๋ฐ ๋ง๋ง ์ ๊ฒฝ ์๊ทน ๊ธฐ๋ฒ์ ์ ํจ์ฑ์ ํ๊ฐํ๊ธฐ ์ํด in-vitro ๋๋ฌผ ์คํ์ ์ค์ํ์๋ค. In-vitro ๋๋ฌผ์คํ์์๋ ๋น์ ์ธ๊ธฐ์ ๋ฐ๋ฅธ ์๊ทน ์ ํธ์ ๋ณ์กฐ๋ฅผ ํตํด ๋ง๋ง ์ ๊ฒฝ์ผ๋ก ์ ์ฃผ์
์ ํ๋์ ์กฐ์ ์ด ๊ฐ๋ฅํ๋ฉฐ, ์คํ ๊ฒฐ๊ณผ ์ฝ 10 nC ์ด์์ ์ฃผ์
์ ํ๋์์ ๋ง๋ง ์ ๊ฒฝ์ ์ ํจ ์๊ทน์ด ์ผ์ด๋จ์ ๊ด์ฐฐํ ์ ์์์ผ๋ฉฐ, ์ด๋ฅผ ํตํด ๋น์ ๊ฒ์ถ ๋ฐ ์๊ทน ์ ํธ ๋ณ์กฐ๋ฅผ ํตํ ๋ง๋ง ์ ๊ฒฝ์ ์๊ทน์ด ํจ๊ณผ์ ์ผ๋ก ์ ์ด๋ฃจ์ด์ง์ ํ์ธํ ์ ์์๋ค.์ 1 ์ฅ ์๋ก
์ 1 ์ ์ฐ๊ตฌ ๋ฐฐ๊ฒฝ
์ 2 ์ ๊ณ ํด์๋ ์ธ๊ณต๋ง๋ง ์์คํ
์ ๊ตฌํ
์ 3 ์ ์ฐ๊ตฌ ๋๊ธฐ
์ 4 ์ ๋
ผ๋ฌธ ๋ด์ฉ ์์ฝ ๋ฐ ๋
ผ๋ฌธ์ ๊ตฌ์ฑ
์ 2 ์ฅ ๋ณธ๋ก
์ 1 ์ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ด ๊ฒ์ถ๊ธฐ๊ฐ ๋ด์ฅ๋ ๊ณ ํด์๋ ๋ง๋ง ์๊ทน๊ธฐ
1. ๊ด ๊ฒ์ถ๊ธฐ๊ฐ ๋ด์ฅ๋ ๊ณ ํด์๋ ์ธ๊ณต ๋ง๋ง ์์คํ
์ ๊ตฌ์ฑ
2. ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ธฐ๋ฐ์ ๊ด ๊ฒ์ถ ๋ฐ ์๊ทน ์ ํธ ๋ณ์กฐ ํ๋ก์ ๋์ ์๋ฆฌ ๋ฐ ๋ง๋ง ์ ๊ฒฝ ์๊ทน ๊ธฐ๋ฒ
์ 2 ์ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ธฐ๋ฐ์ ๊ด ๊ฒ์ถ ํ๋ก๊ฐ ๋ด์ฅ๋ ๋ง๋ง ์๊ทน๊ธฐ์ ์ค๊ณ
1. ๋ด๋ถ ๊ด ๊ฒ์ถ๊ธฐ๋ฅผ ์ด์ฉํ๋ ๋ฐฉ์์ ๋ง๋ง ์๊ทน๊ธฐ์ ์ค๊ณ
2. ๋ด๋ถ ๊ด ๊ฒ์ถ๊ธฐ์ ์ธ๋ถ ์นด๋ฉ๋ผ๋ฅผ ์ ํ์ ์ผ๋ก ์ด์ฉํ ์ ์๋ ๋ฐฉ์์ ๋ง๋ง ์๊ทน๊ธฐ์ ์ค๊ณ
์ 3 ์ ๋ง๋ง ์๊ทน๊ธฐ ๊ฐ ๊ตฌ์ฑ ์์๋ณ ์์ ์ ์ ๋ฐ ํน์ฑ ํ๊ฐ
1. ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด์ ์ ์
2. ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ด ๊ฒ์ถ๊ธฐ ์ ์ ๋ฐ ํน์ฑ ํ๊ฐ
3. ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด FET ์ ์ ๋ฐ ํน์ฑ ํ๊ฐ
4. ๊ณ ๋ฐ๋ ๋ฏธ์ธ ์ ๊ทน์ ์ํ ๋๋
ธ 3D ์ ๊ทน ์ ์
์ 4 ์ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ธฐ๋ฐ์ ๊ด ๊ฒ์ถ ๋ฐ ์๊ทน ์ ํธ ๋ณ์กฐ ํ๋ก ์ ์ ๋ฐ ํน์ฑ ํ๊ฐ
1. ์ ์ ๋ถ๋ฐฐ๊ธฐ ๋์ ์ํ
2. ์ ๋ฅ ๊ตฌ๋๊ธฐ ๋์ ์ํ
์ 5 ์ ์ค๋ฆฌ์ฝ ๋๋
ธ์์ด์ด ๊ด ๊ฒ์ถ๊ธฐ๊ฐ ๋ด์ฅ๋ 32ร32 ๊ณ ํด์๋ ๋ง๋ง ์๊ทน๊ธฐ์ ์ค๊ณ ๋ฐ ์ ์
1. 32x32 ๊ณ ํด์๋ ๋ง๋ง ์๊ทน๊ธฐ์ ์ค๊ณ
2. 32x32 ๊ณ ํด์๋ ๋ง๋ง ์๊ทน๊ธฐ์ ์ ์
์ 6 ์ In-vitro ๋๋ฌผ ์คํ์ ํตํ ๋ง๋ง ์๊ทน๊ธฐ์ ์ ํจ์ฑ ํ๊ฐ
1. In-vitro ๋๋ฌผ ์คํ ์ฅ์น ์
์
๋ฐ ๋ง๋ง ์ ๊ฒฝ ์๊ทน ์คํ
2. ์๊ทน ์ ํธ์ ๋ถ์ ๋ฐ ๋ง๋ง ์๊ทน์ ์ ํจ์ฑ ํ๊ฐ
์ 3 ์ฅ ๊ฒฐ๋ก
์ 1 ์ ๊ฒฐ๊ณผ ์์ฝ
์ 2 ์ ํฅํ ๊ณํ
์ฐธ๊ณ ๋ฌธํ
AbstractDocto
Dielectrophoresis Control of Semiconductor Nanowires for Sensing Technology
Semiconductor nanowires (NWs) synthesis successes have given keys to unprecedented nano-scale sensitivity opening up new opportunities in device applications. NWsโ potential relies upon the possibility of engineering and modifying properties such as sensitivity and carrier transport, by tailoring the NWsโ morphology and conductivity. New challenges have taken place with the downscaling of electronics for NWs integration and assembly techniques. Amongst a large variety of integration techniques, dielectrophoresis (DEP) is a powerful tool for the precise manipulation of NWs of different compositions and sizes. However, experimental implementation and analysis with DEP often lack depth regarding the optimisation of the technique and the effects of the parameters on the performances of the final devices, which is crucial for the understanding of NWsโ electric transport properties and technology improvement.
Consequently, this thesis presents a comprehensive study of the experimental implementation of DEP which is of paramount importance to obtaining optimum conditions for NWs alignment. With this aim in mind, the presented work demonstrates a detailed investigation of the electrical and optical properties of germanium (Ge) and gallium-arsenide-bismuth (GaAsBi) NWs-based devices by DEP as a function of the collection frequency. The Ge and GaAsBi NWs were obtained by MOVPE and MBE respectively as a collaborative work with the Institute of Material for Electronic and Magnet (Italy) for the Ge NWs, and with the research team of Dr Robert Richard at the University of Sheffield (Department of Electrical Engineering and Electronics) for the GaAsBi NWs.
Firstly, to maximise NWs alignment precision, optimum DEP parameters are for the first time thoroughly extracted by testing the effects of different mediums (chemical inertia, volatility and contact angle) and electrode designs (gradients and electric field).
Secondly, fabricated with a DEP frequency range of 500 kHz to 10 MHz the devices were electrically characterised using voltage-current response. An asymmetric diode-like behaviour was found to be originating from heterostructured Ge NWs specifically orientated by electrophoresis combined with DEP. This result is particularly promising for orientation control demonstrated for the first time, tuning and altering current response from chemically heterostructured nanowires.
A particular focus was given to the effect of increasing frequency on the device performances such as carrier transport. Despite a decrease of aligned NWs corroborating theoretical analysis, increasing frequency collected higher conductivity Ge NWs with carrier mobility improving from 2ฮธ at 500 kHz to 4.38ฮธ at 10 MHz demonstrated using Mott-Gurney, and GaAsBi NWs with carrier mobility increasing from 5.29 ยฑ 0.027 to 100 ยฑ 0.70 cm2 Vโ1.sโ1 at 500 kHz and 10 MHz demonstrated using the Fermi-velocity law. Such selectivity is of great potential to improve sensing technology transduction.
Using optimum parameters previously found, a low-cost and simple voltage divider system joined to DEP is demonstrated for the first time to improve the alignment technique of a single Ge nanowire. The resulting spectral response was consistent with optical characterisations found in the literature for a single Ge nanowire and demonstrated high sensitivity near-infrared and communication wavelength as confirmed with a high responsivity of 6.2 x 105 A/W at 1550 nm. Such high resistivity is amongst the highest ever obtained for NWs.
Furthermore, a NWs-based biosensor for the spike protein of the SARS-CoV-2 was fabricated by multilayered surface functionalisation evidenced by Raman spectroscopy. Upon exposure to increasing concentration of the protein, the biosensors transduced increasing current response with a working range of at least 1 aM to 100 fM. Selectivity to the spike protein was testified using bovine serum albumin as a negative control reference.
The GaAsBi NWs were for the first time fully characterised and implemented as devices by DEP. The NWs surface roughness showcased the importance of surface properties that influenced DEP collection and carrier transport. Spectral responses from the devices brought to light the different bismuth content at the origin of reduced band-gap energy shown by the cut-off energies of the spectrum. With a Bi content increase of roughly 1% in GaAs the photodetectors presented high responsivity from 1.3 x 104 A/W to 5.6 x 104 A/W.
Effective NWs-based biosensors and photodetectors were proof of concept devices that corroborate NWs and dielectrophoresis functionality paving the way to future nanotechnology improvement