Auxiliary Electrode Field Control for Silicon Sensor Recombination
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Solution Overview
Problem
Existing biosensors for protein sensing are limited by ease of use, availability of low-cost tests, and reliability, and none meet all market needs simultaneously, particularly due to high recombination rates at unpassivated or weakly passivated silicon surfaces which reduce photocurrent generation.
Innovation Solution
A silicon p-n junction biosensor is enhanced by applying an external electric field through an auxiliary electrode, which repels minority carriers and increases photocurrent by altering surface passivation, using a linker to bind proteins and create an electric field, and utilizing silicon nanowires for high sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the silicon surface is unpassivated or weakly passivated to allow protein binding, then the surface can effectively detect analytes through charge effects, but the recombination rate increases and photocurrent is reduced
Solution Approach 1:
The patent applies different passivation qualities to different regions of the silicon surface. The binding region remains unpassivated or weakly passivated to allow protein analyte detection through charge effects, while other regions receive enhanced passivation to reduce recombination and maintain photocurrent generation. This spatial differentiation resolves the contradiction between detection sensitivity and energy loss.
Solution Approach 2:
The patent introduces an intermediary layer or structure that mediates between the unpassivated binding surface and the passivated regions. This intermediary enables the coexistence of high recombination activity at the binding interface (for analyte detection) and low recombination elsewhere (for photocurrent generation), thus resolving the contradiction.
2Measurement precision
If an auxiliary electrode is added to apply external electric field, then photocurrent signal is enhanced, but device complexity increases
Solution Approach 1:
The auxiliary electrode is designed to serve multiple functions: it applies the external electric field to enhance photocurrent, provides a reference potential, and can potentially serve as a protective electrode. By making this single component multi-functional, the patent reduces the need for additional separate components, thereby limiting the increase in device complexity while achieving signal enhancement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances photocurrent signal and sensitivity, allowing for more accurate and reproducible protein detection, with a lower detection threshold of 10 ng/ml to 1 fg/ml, suitable for medical diagnostics and biomanufacturing applications.
Implementation Method 1
A promising sensing modality is using photocurrent generated by a photovoltaic device and the change in photocurrent generated by the photovoltaic device when solutions with an antigen of interest are present
Implementation Method 2
The electrical charge that is now bound to the surface of the silicon through the linker will create an electric field inside the silicon and repel like charges
Implementation Method 3
An unpassivated or weakly passivated surface of a photovoltaic device, also referred to as a solar cell herein, serves as a very effective recombination site for photocarriers. The high recombination rate in the vicinity of a surface depletes this region of minority carriers.
Implementation Method 4
When light is incident onto the silicon surface, it creates electron-hole pairs. If those electron-hole pairs separate and are collected out of the contacts of the device, they create photocurrent.
Data Source
AI summary
Provided is a biosensor with an auxiliary electrode that can increase the photocurrent signal of the biosensor due to the presence of analytes of interest.