3. REQUIREMENTS AND CRITERIA FOR OPTICAL TWEEZERS
3.1 – Existing Optical Tweezers Experiment, its Limitations, and Requirements Development
(WHY WE CHOSE THIS EXP) – is it a mandatory course?
The existing optical tweezers apparatus, Optical Trapping Kit by Thorlabs, is a new lab within the
Department of Physics that has been designed for use in an advanced teaching laboratory. The equipment
has been tested, however, there is currently no provision for laser safety. The optical tweezers employ a
980nm trap laser with a maximum power output of 330mW. According to the manufacturer, the laser
beam is predominantly encased by lens tubes, is not operated at the maximum power, and an exposed
beam diverges after encountering the sample. As such, the system is considered to be a Class 1 laser when
fully assembled and functioning appropriately [H2]. A Class 1 laser is enclosed to prevent contact
between a person and the exposed laser beam [H1]. High-powered lasers are also included in this
classification, so long as the enclosure prevents exposure and cannot be opened without turning off the
laser. If the trap is not completely assembled or the laser beam is exposed, the system is classified as a
Class 3B laser (power is 5-500mW) and is considered hazardous. This may be the case while a user
performs beam alignment. Thus, this system requires a set-up that is safe for undergraduate student use
and can be classified as a Class 1 laser.
Furthermore, a protocol for the optical tweezers experiment was developed by ______ [name of summer
student], an ____(undergrad?) summer student. This experiment will be utilized by the Department of
Physics for the 3rd/4th year Advanced Physics Laboratories (course code) upon achieving a laser safe setup. Thus, the existing protocol must be tested and revised to include safety precautions and appropriate
details.
Which course will it be used for? [H3]
PHY327/427/428/429 (Engineering)
PHY424/426/428/429 (A&S)
*interlock from being on when exposed
3.2 – Optical Tweezers Equipment Constraints
The following are technical constraints for the optical tweezers apparatus, developed in consultation with
Professor Bailey, Sandu Sonoc and Professor Ryu:
A1
A2
A3
 The Optical Tweezers experiment must be made safe for undergraduate students who have
not taken the full day laser safety course and should be classified as a Class 1 laser.
 The optical tweezers employ a 980nm laser with a maximum power output of
330mW. If the laser is exposed, it is considered a Class 3B laser. Appropriate
measures must be taken to enclose the optical path of the beam. If the enclosure is
opened for beam alignment, the laser power output must be reduced to 5mW (Class
1).

 The light path where the beam is exposed to air should be enclosed.
 The fibre optic should be enclosed. It would be helpful to be able to observe the fibre optic
under the enclosure.
A4
A5
A6
A7
 The beam enclosures are to be locked or sealed with security screws as the beam will be
pre-aligned.
 The reflected beam should not leak out from the sample stage, and the user must be able to
move the sample stage using the knobs.
 There are x, y, and z knobs for sample stage movement. These must be accessible
when the beam is on.
 Budgetary constraints: Additional components added onto the existing apparatus should not
exceed CDN $1000.
 You will want to think about what silly things students might do. The one that immediately
came to mind is that if something wasn't working, some student might start disassembling
things to see what is wrong, e.g. remove the top camera mount and look down. Your design
needs to prevent (i.e. make difficult) such things, while allowing students to do what they
need to do with as little hindrance as is consistent with safety.
3.3 – Experimental Constraints
The optical tweezers experiment is designed for use by students in the Undergraduate Advanced Physics
Laboratories (APL). The goals for the APL include presenting the student with the “opportunity to work
on interesting and challenging experiments, deepen their understanding of the underlying Physics, and to
further develop laboratory, analysis and communication skills.” [H3]. As well, the “experiments in this
course are designed to form a bridge to current experimental research. A wide range of experiments are
available using contemporary techniques and equipment. Many of the experiments can be carried out with
a focus on instrumentation.” [H5]. As such, the following development of constraints that constitute a
“good laboratory experiment” ranging from experimental constraints, to the experimental protocol and
method of evaluation will reflect the objectives of the APL as well as approaches considered in
educational journals.
Experiment Constraints:
B1
B2
B3
B4
B5
B6
B7
 The experimental procedure should be within 18 hours over the course of 3 weeks.
 Advanced Physics Laboratory structure.
 The room door must be closed and locked with a temporary “Laser Work in Progress” sign
placed outside the room door.
 This sign can be provided by Sandu Sonoc, the Senior Radiation Safety Officer.
 Appropriate laser safety glasses must be worn at all times when using the equipment.
 The beam will be pre-aligned prior to the student commencing the lab.
 The beam should be turned off when changing samples.
 Changing the sample involves moving somewhat reflective material in and out of
the beam path. The beam must be turned off when this occurs. Normally, no light
should reflect out when changing the sample, but there is a chance that if someone
sticks something in (eg. A pen to indicate the beam position), then inserting an
object may cause the beam to reflect wildly.
 The laser power supply key should be kept by the technologist.
 The experiment should be carried out individually.
 In accordance with APL structure.
Student Assessment:
C1
C2
C3
C4
 The mark composition for the laboratory should not be completely data-driven, and should
include a combination of data analysis within the student’s lab notebook as well as more
general questions pertaining to the lab that assess the student’s understanding. It should also
include a discussion with the TA/Professor regarding the results obtained.
 This is in accordance with APL structure, and the consultation with the
TA/Professor would enhance oral and written communicability of technical
material [H6].
 Adequate time must be provided to the student for completion of the lab write-up.
 Pre-lab??? Or shouldn’t include this?
 The write-up should include a brief discussion of a research paper that utilizes Optical
Tweezers to bridge the experiment to current experimental research [H5].
Experimental Protocol:
D1
D2
D3
D4
D5
D6
D7
 Clear and succinct safety instructions must be given to the students through the
experimental write-up, from the instructor, and displayed on the wall near the equipment.
 The experiment should present a challenge in figuring out the instrumentation and include
more general instructions rather than a detailed procedure so as to be more engaging.
 This is in accordance with the APL structure.
 Learning style??
 The entire experiment should be divided into sections or a series of experiments that
investigate different concepts.
 The experiment should not be repetitive or tedious.
 A more detailed experimental protocol should be provided to the TA/Professor to enable
them to assist the students when necessary. This should detail the potential pitfalls that may
be encountered [H4].
 The protocol should include the background and theory pertaining to the lab, as well as
clearly detailed schematics of the apparatus. [H4]
 A list of relevant websites that will aid the student in understanding the laboratory concepts
or equipment should be included.
 The experiment should incorporate a variety of skills and techniques [H4].
Training:
E1
E2
E3
 The TA/Professor present during the laboratory session should be well acquainted with the
experimental procedure and apparatus and should be available for assistance.
 The student must require minimal initial training in order to execute the lab.
 An introduction to the lab should be given by the TA/Professor to acquaint the student with
the lab concepts, the equipment, expectations and clearly stated safety instructions.
Appendix:
Figure #: Optical trapping kit by Thorlabs, including ITC-510 controller [H2].
Figure #: Schematic diagram of Optical Trapping kit Optical trapping kit by Thorlabs, including
ITC-510 controller [H2].
7.5 – Team Qualifications (CV statements and courses taken)
Courses completed:
ESC101, MAT194, PHY180, ECE159, ESC102, ECE352, AER201, ESC202, ECE360,
BME340, BME496, <<ADD everyone else’s – optics, Shannon>>.
Technical competencies and other relevant experience:
- Hasmita:
o Electromechanical member of design team for AER201
o Use of iterative approach for system development
o Experience with Cellular and Molecular Bioengineering lab protocols and
designing a protocol for engineering nanoparticles with specific properties
o Teaching Assistant at UofT’s da Vinci Engineering Enrichment Program (DEEP)
for Medical, Bio-medical and Chemistry courses for students in grades 9-12
o Assistant teacher at Xincon College – developed course material and lectures
o Tutored several middle-school students in Math, English, Social Studies and
French
- Laura:
o Laser Safety training
o Electromechanical member of design team for AER201
o
- Shannon:
o Responsible for creation of circuitry for AER201
- Maryam:
o Electromechanical member of design team for AER201
o
Overall Abilities:
- Strong leadership abilities and organizational skills
- Ability to carry out tasks logically and systematically through research and incorporation
of client feedback
- Experience working efficiently in a multidisciplinary team
- Experienced with development of technical documentation for design projects and
presentations to client
- Excellent oral communication and interpersonal skills
- Proficiency in: MS Office 2007, MATLAB, <<programming, circuits, etc.>>, Labview?
References:
[H1] http://www.lasermet.com/resources/classification_overview.php
[H2] http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=3959
[H3] http://www2.physics.utoronto.ca/~phy326/
[H4] E. Bell, “Laboratory Exercises”, Biochemistry and Molecular Biology Education, vol.
29, no. 3, 2001. [Online]. Available: http://onlinelibrary.wiley.com/doi/10.1111/j.15393429.2001.tb00086.x/pdf. Accessed Sept 26, 2010.
[H5] Engineering Academic Calendar 2010 – 2011
http://www.undergrad.engineering.utoronto.ca/Assets/UndergradEng+Digital+Assets/calenda
r1011/Chapter+8.pdf
[H6] Panel on Undergraduate Engineering Education, Committee on the Education and
Utilization of the Engineer, Commission on Education and Technical Systems, National
Research Council. Engineering Undergraduate Education. Washington, DC: National
Academy
Press,
1986,
pp.82.
[Online].
Available:
http://www.nap.edu/openbook.php?record_id=589&page=82. Accessed Sept 26, 2010.