This Immersion site will focus on biophysics and soft matter experiments. You will be exposed to five biophysics/soft matter experiments, but will choose one to focus on during the two days. For the one you choose, mentors will walk you through how to use the instrument and make a biological or soft matter sample for test. By the end of the two days, you should be able to use the instrument, complete experiments on your own, and teach someone else how to use the instrument. This Immersion should be great for:

·         Instructors who are interested in biophysics or soft matter, but have no background in the field

·         Instructors who have wanted to add a biophysics or soft matter experiment to an advanced lab class, but haven’t done so yet

·         Instructors that are interested in biophysics or soft matter projects with undergrads  

·         Instructors who have done biophysics or soft matter research and are interested in learning a new technique

 The experiments in this Immersion (see Figure 1) are the experiments we use in the BCBP/PHYS 333 Biophysics with Lab course for juniors at Amherst College. The experiments are:

1)      Atomic Force Microscope (AFM). This is a versatile research microscope in which a sharp tip scans along the surface with atomic resolution to produce an image. AFMs can measure everything from soft biological samples like DNA and proteins to hard ceramics. AFMs can also measure force and are useful for quantifying properties like adhesion, hardness, and friction. AJP article here.  

2)      Rheometer. This is a research instrument used in industry to measure the viscoelasticity of cosmetics, paint, gums, slurries, lotions, condiments, pastes, and many other food products. Typically, a rheometer consists of two plates, where the top plate is rotated relative to a bottom plate to produce a shear force. Shear stress (force per area) can then be plotted against a strain rate to measure viscosity or viscoelasticity. This lab is a student favorite!

3)      Texture Analyzer. This is a research instrument that applies either a tensile or compressive stress and measures a tensile or compressive strain to get the elasticity of a material. Soft matter samples like foods and cosmetics as well as biological samples of cellulose, keratin, or collagen can be measured. This lab is a student favorite!

4)      Acoustic Trap. This is a simple apparatus where a piezo applies an acoustic force to microscopic particles confining them to a particular location. Visualizing these particles with a microscope allows measurement of the trapping force and motion. AJP article here.

5)      Brownian motion experiment. This is a classic experiment where students track particle motions in water using a microscope. If there is one experiment you should add to your repertoire it is this experiment! Tracking particle motions is a great jumping off point for talking about thermal motion, the Boltzmann constant, normal diffusion vs. subdiffusion, the random walk, viscoelasticity, and much more. Here we will also do simulations along with theory to address the error in the experiment. AJP article here.

Figure 1. Instruments. A) In AFM, a sharp tip scans across a surface to take a profile in x. Many scans create an image in x-y. B) In an acoustic trap, a piezo is placed on top of a chamber. Tuning the frequency of the piezo creates a standing wave in the chamber, which traps particles. C) Brownian motion measurements require tracking of particles in a sample chamber using a microscope.

a)             Basic Physics – Biophysics is the study of the physics of biological systems. Soft matter physics is concerned with materials that are easily deformed by thermal fluctuations or external forces, such as polymers, gels, foams, and biological materials. In this immersion, we will talk about the three modules in the Biophysics with Lab course at Amherst College. These modules are on optics, random walks, and force—three topics that physicists know well! We will talk about how we introduce these topics and the laboratory experiments to both premed and physics students.

b)            Importance – Soft matter physics is one of the fastest growing fields in physics. Researchers in this field look at the physical properties of polymers, colloids, surfactants, liquid crystals, and amphiphiles. They study self assembly, non-equilibrium dynamics, material activation, wetting, tension, and viscoelasticity. However, there are very few soft matter experiments in the undergraduate laboratory. At the same time, with the advent of more computational power there has been an explosion in biophysics and a need for people to simulate the motions of molecules. Adding soft matter and biophysics experiments to an advanced lab course is a great way to get students interested in these important fields.   

 

c)             Skills that will be acquired – Participants will get a general overview of biophysics taught in the Biophysics with Lab course. Then, participants will dive into their specific experiment and learn how to use the experiment, take data, troubleshoot, and teach the physics surrounding the experiment.

 

d)            Outline the Immersion:
Day 1 (Morning) – meet everyone! Go over the material in the Biophysics with Lab course that starts by teaching topics physicists know—optics, random walk, and force. Then go over the segues into microscopy, tracking, and force measurement.
Day 1 (Afternoon) – complete the 3-hour laboratory the students in the course complete along with a mentor.
Day 2 (Morning) – spend more time on the experiment either on the biology or the equipment, whatever the participant needs. If participants bring samples they want to test, we will test it then.
Day 2 (Afternoon) – finish taking data. Walk through of all of the experiments in the Immersion.

 

e)            What to bring – Participants will benefit from bringing their own laptop computers to take notes, download software, and perform calculations, but laptops are not necessary.

 

f)              Safety considerations – General lab safety procedures will need to be followed. Clothing should be closed toed shoes, pants or long skirts, and long sleeves.

g)             Cost estimate for the equipment – 

a.       AFM – Many institutions have a microscopy center or have access to a microscopy center with an AFM, teaching AFMs are $25k, research AFMs are $100k-$500k. Will we use an Asylum Cypher and an Asylum MFP-3D.

b.       Rheometer – Simple rheometers are <$2k while research grade instruments are $25k. We will use an Anton Paar MCR 92.

c.       Texture analyzer – Simple tensile testers are <$2k while research grade instruments are $25k. We will use an XT from Texture Technologies, as well as a simple tensile tester.

d.       Acoustic trap – piezos are very cheap at $25 and the whole setup is <$2k, research grade instruments use more expensive function generators

e.       Brownian motion – setup <$2k, classroom grade or research grade microscopes are nice for this but not necessary.