Silicon-based pH sensor for biological and environmental applications

Gorti, Tejaswi

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https://hdl.handle.net/2142/34249 Copy

Description

Title

Silicon-based pH sensor for biological and environmental applications

Author(s)

Gorti, Tejaswi

Issue Date

2012-09-18T21:07:52Z

Director of Research (if dissertation) or Advisor (if thesis)

Liu, Gang Logan

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Silicon
• semiconductor
• fabrication
• solid state
• device physics
• biosensors
• nanotechnology
• microfluidics
• pH
• carrier transport
• Metal-Oxide-Silicon (MOS) capacitor

Abstract

In biological and environmental applications, it is desirable to be able to measure hydrogen and hydroxyl ion concentrations (pH levels). Conventionally, the measurement processes take a considerable amount of time involving several calibration steps and handling of fragile electrodes. Here we propose a new, more robust and theoretically reliable way of sensing pH. Following a similar approach to Dr. Qingjun Liu’s work on the light-addressable potentiometric sensor (LAPS) from the Zhejiang University in China, we fabricated a silicon pH sensor, with polydimethylsiloxane (PDMS) fluidic channels for solution delivery and testing. Particularly for biological and environmental applications, the range of pH sensing is confined to 6 to 8. The fabricated device used n-type silicon, so only five acidic solutions between pH 5 and pH 7 were tested. Device test results proved to be somewhat problematic. We were not able to obtain consistent capacitance measurements for a particular pH solution. For some solutions we had extremely large variances in capacitance, yielding “noisy” measurements. However, in retrospect, there are many improvements that could be made to our device and testing procedure in order to obtain more consistent capacitance readings, closer to the theoretical performance. Such changes include modifying the geometry of the electrode which supplies an AC signal for capacitance measurements, and ensuring airtight (PDMS) bonding with the device substrate, guaranteeing seamless solution delivery to the test chamber. It is our hope that future students are able to build upon these results and create a better, more reliable device.

Graduation Semester

2012-08

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http://hdl.handle.net/2142/34249

Copyright and License Information

Copyright 2012 Tejaswi Gorti

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