1. Introduction
Methods
Conclusion
Purpose
References
Results
• Photonic crystal nanostructures are essential in
combining two important technologies: optical
tweezers and MEMS resonators to allow effective
trapping and enhanced-precision measurements
of cell mass.
• MEMS resonators measure the cell mass by
detecting the resonant frequency change of a
resonant beam [1].
• Photonic crystal optical tweezers are applied
to improve the mass sensing capability of
MEMS resonators by fixing the cell position
with low light intensity [1].
• Biological Applications include manipulation and
identification of living cells, parallel manipulation
of DNA strands and nanoparticles [2], and
identifying cell characteristics [3].
• National Science Foundation, Grant No. ECCS0335765
• National Nanotechnology Infrastructure Network
• NNIN Principal Investigator: Lih Y. Lin
• NNIN Mentors:
• Ethan Keeler
• Peifeng Jing
• Conner Ballew
• Jingda Wu
Acknowledgements
Figure 1: Preliminary Beam Resonator supporting
a channel structure
Figure 5: Optical Trapping of Yeast Cells in 3-by-3
dot formation
• Utilizing photonic crystal optical tweezers with
MEMS resonator microstructures to effectively
enhance optical trapping to determine
characteristics of differing cells.
• Changes in mass distribution on the MEMS beam
cause resonant frequency shifts [2].
• As the laser beam goes through the microscope
and fixates on cells, a separate laser beam
incidents onto the vibrating resonator and
produces an optical deflection signal (ideally
resembling a sinusoidal wave) upon hitting a split
photodiode on the detection circuit.
• This detection system serves to measure the
resonant frequency of a micro-machined
resonator.
• [1] Peifeng Jing, et al. “Optical Trapping on Two-
Dimensional Photonic Crystal and Cell Viability
Characterization” Optics in the Life Sciences, OSA
Technical Digest (online) (Optical Society of
America, 2015), paper OtT4E.4.
• [2] Pei Yu Chiou, et al. Nature, 436, 370-372, 2005
• [3] Ethan G. Keeler, et al. Bio-Optics: Design and
Application (BODA), Vancouver BC, Canada, 2015
• The enhanced detection circuit contains five
components: a voltage divider, two
transimpedence amplifiers, a difference amplifier
and a comparator.
• A brief format of the circuit components is
presented:
• The image below shows the AC coupling of the
waveforms.
• The detection circuit in Multisim simulation
produced an output signal sinusoidal wave
(cerulean color) from the difference amplifier
with a direct current (DC) voltage of five volts,
centered at 2.5 volts (shown during DC
coupling).
• As the signal output from the difference
amplifier travels through the comparator, a
square wave (magenta color) signal output is
produced.
• Time base: five microsecond per Division
• Scale for Difference Amplifier output: two
volts per Division
• Scale for Comparator output: 500 millivolts
per Division
• Using an Arduino microcontroller, the circuit is
programmed to detect resonant frequency
dependent upon the high and low values of the
square wave.
Figure 4: Detection Circuit
• With the detection of the resonant frequency, various
cells can be observed and recorded, providing
information that can identify cells and their
characteristics.
• The next step in this process is to test the detection
circuit on the optical set up to enhance the durability
and efficiency of the circuit.
• While there are issues with cell viability in terms of
optical trapping of cells, such as cell mortality, cells
sticking to the bottom of slides, etc., there is great
evidence that photonic crystal optical tweezers will
not only be able to distinguish different types of cells,
but also serve as a treatment to microscopic
procedures.
• The detection circuit originally contained three
components: two transimpedence amplifiers and a
difference amplifier.
• Original signal output at the difference amplifier:
square wave (instead of a sinusoidal wave).
• The detection circuit was enhanced during a series
of phases using the software Multisim:
• Phase 1: Original Schematic Design
• Phase 2: Changing Alternating Current (AC)
power supply to a DC power supply
• Phase 3: Adding voltage dividers, adding a low
pass filter to counteract noise
• Phase 4: Integrating two voltage dividers,
establishing unified power supply for the
transimpedence amplifiers
• Phase 5: Maintaining five volts throughout the
circuit with a voltage buffer, inserting a
comparator to change the sinusoidal waveform
into a square wave, increasing the frequency of
the AC current source from 1 kHz to 300 kHz
(split photodiode)
• Phase 6: Correcting the cut-off frequency for the
low-pass filter, lowering the gain
• Phase 7: Organizing the circuit/schematic
• An Arduino microcontroller will input the square
wave (from comparator) and count the frequency.
Figure 2: Simplified Schematic Circuit
Figure 3: Signal Outputs from Multisim
Simulation Oscilloscope