A Caltech Library Service

On-Chip Integrated Label-Free Optical Biosensing


Sendowski, Jacob Benjamin (2013) On-Chip Integrated Label-Free Optical Biosensing. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/2H9Y-AB63.


This thesis investigates the design and implementation of a label-free optical biosensing system utilizing a robust on-chip integrated platform. The goal has been to transition optical micro-resonator based label-free biosensing from a laborious and delicate laboratory demonstration to a tool for the analytical life scientist. This has been pursued along four avenues: (1) the design and fabrication of high-$Q$ integrated planar microdisk optical resonators in silicon nitride on silica, (2) the demonstration of a high speed optoelectronic swept frequency laser source, (3) the development and integration of a microfluidic analyte delivery system, and (4) the introduction of a novel differential measurement technique for the reduction of environmental noise.

The optical part of this system combines the results of two major recent developments in the field of optical and laser physics: the high-$Q$ optical resonator and the phase-locked electronically controlled swept-frequency semiconductor laser. The laser operates at a wavelength relevant for aqueous sensing, and replaces expensive and fragile mechanically-tuned laser sources whose frequency sweeps have limited speed, accuracy and reliability. The high-$Q$ optical resonator is part of a monolithic unit with an integrated optical waveguide, and is fabricated using standard semiconductor lithography methods. Monolithic integration makes the system significantly more robust and flexible compared to current, fragile embodiments that rely on the precarious coupling of fragile optical fibers to resonators. The silicon nitride on silica material system allows for future manifestations at shorter wavelengths. The sensor also includes an integrated microfluidic flow cell for precise and low volume delivery of analytes to the resonator surface. We demonstrate the refractive index sensing action of the system as well as the specific and nonspecific adsorption of proteins onto the resonator surface with high sensitivity. Measurement challenges due to environmental noise that hamper system performance are discussed and a differential sensing measurement is proposed, implemented, and demonstrated resulting in the restoration of a high performance sensing measurement.

The instrument developed in this work represents an adaptable and cost-effective platform capable of various sensitive, label-free measurements relevant to the study of biophysics, biomolecular interactions, cell signaling, and a wide range of other life science fields. Further development is necessary for it to be capable of binding assays, or thermodynamic and kinetics measurements; however, this work has laid the foundation for the demonstration of these applications.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:sensing;biosensing;optical microresonators;swept frequency laser sources;
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Yariv, Amnon
Thesis Committee:
  • Yariv, Amnon (chair)
  • Yang, Changhuei
  • Flagan, Richard C.
  • Scherer, Axel
  • Crosignani, Bruno
Defense Date:28 May 2013
Funding AgencyGrant Number
National Science Foundation1152623
Record Number:CaltechTHESIS:05312013-213433052
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7812
Deposited By: Jacob Sendowski
Deposited On:06 Jun 2013 23:45
Last Modified:04 Oct 2019 00:01

Thesis Files

PDF - Final Version
See Usage Policy.


Repository Staff Only: item control page