The Business Case #1: Entering a New Market

1. Whenever a company wants to enter a new market, the company needs to have a cogent reason to do so.  So the first responsibility as a consultant, is to clearly understand this reason.

2. Generally, entering a new market always comes down to increasing profits—as should the majority of business decisions.  Thus, if we expect this new market to equal more money for us, we need to do a good market analysis, to determine whether or not it is attractive.  In this market analysis we should be looking for:

• The size of the market
• The growth rate
• The stage of development
• Who the market serves (customers)
• Average margins

3. Then once we have determined the overall attractiveness of the market, we want to know whether or not the market is attractive to us.  This will involve a competitor analysis and an assessment of how this new venture will affect our current operations.  Look for the following:

• competitor analysis
  • list of competitors
  • their products
  • their market shares
• barriers to entry?
• barriers to exit?
• how do we price/differentiate our product?

4.  If we do decide to enter the market, then we have 3 choices as to how to enter the market:

• develop the business in house
• Acquisition
• Joint Venture

 

Summary

1. Why does the company want to enter this market
2. General Market Analysis
3. How this market makes sense to the company
4. How to enter the market

The Business Minded Bioengineer

I am a bioengineer, indeed.  But I don't think like one.  My brain doesn’t tick like one, and my heart doesn’t flutter at the notion of fluid dynamics and calculating the recycling rate of a drug in the body. 

I’m sure that there are a lot of others out there like me, and that’s why I’m writing this.

I care more about the application of science into life, than the discovery of knowledge for it’s sheer ingenuity.  I would rather take a drug to market, than settle the long standing debate about Pluto being a planet or not.

It might be short-sighted on my part—part of my childish need to seek instant gratification.  Maybe it’s just because I’m shallow, and materialistic and find that business is a much more lucrative path than academia.

Whatever it may be, there is definitely a need for someone translate what is learn into what can be utilized.  That’s part of what being an engineer is anyways.  Engineers were always more application oriented than theoretical.  Engineers take equations derived previously and use them to create tangible products.  And the business minded engineers take those tangible products and help them achieve adoption in society.

The basics for any type of business strategy, believe it or not, can be tackled with the ever famous case-interview.  For those not familiar with consulting, a case-interview is when job-candidates are presented with a mock business case to solve within the span of 30min-1hour.

The types of cases can be broken down into the following.  And we will be going over each.

1. Entering a New Market
2. Industry Analysis
3. Mergers and Acquistions
4. Developing a New Product
5. Pricing Strategies
6. Growth Strategies
7. Starting a New Business
8. Competitive Reponse
9. Increasing Sales
10. Reducing Costs
11. Increasing Profits
12. Turnarounds

Biomaterials: Phase Diagrams

I remember mentioning before something about the stress-strain curve being the single most important thing you need to understand in material science.  Well, add phase diagrams to the list of single most important won’t ya?  (Trust me, I get that you can’t have two single most anythings)

When materials are made of two types of elements they form either a solution or a mixture.  Often times the two are related as in the following phase diagram.

 

A Solution is when the two materials are maintained in a single phase.

There will be a breaking point where either there is too much concentration of the solute or the temperature is too low, and the solution will split into two phases.

A mixture is when materials are combined, but more than one phase is observed.

That point of transition is called the solubility limit.  On the phase diagram above, the solubility limit at temperature = 20 degrees celsius is marked.  We see that at 20 degrees Celsius, any ratio of more than 65% sugar by weight, will take the single phase syrup into a liquid + sugar mixture.

Just some simple terminology to get out of the way

• components: the elements or compounds which are present in the mixture
• phases: the physically and chemically distinct regions

 

Types of Phase Diagrams

This is a Binary phase diagram.  There are only two components: 1 solid and 1 liquid.

This is a Binary Eutectic phase diagram.  There is 1 liquid and 2 solids.  The eutectic point is the point where the liquid phase transitions directly to the solid phase.  ( Hint: it’s the bottom of the v shape, or if you prefer, the flying birdy)

Other types of phase diagrams are Eutectoid and Peritectic.  I apologize as I do not have diagrams for those two right now. 

A eutectoid phase diagram is characterized by 1 solid phase in equilibrium with 2 other solid phases.  So in this case the 1 solid phase will transition immediately into 2 solid phases.

A Peritectic reaction is where (1 solid + 1 liquid) are in equilibrium with another solid.  So (1 solid + 1 liquid) –> totally different solid.

 

The Lever Rule

The lever rule and the tie line are used to determine the phase composition of any point in the phase diagram

In the above diagram we are concentrating on point B (in the center).  Say we want to figure out what the phase composition is at point B.

The first thing that you want to notice when you look at the diagram is that this is a binary phase diagram, with 1 liquid phase and 1 solid phase.  Point B is in the middle biphasic region.  To figure out the percent composition we draw a tie line.

A tie line is an isothermal line connecting the compositions of two phases in a two phase field.  Looking at the tie line, we can see that Point B is disproportionately closer to the liquid phase than the solid phase.  If you can imagine the tie line as a lever and Point B as the pivot, then the liquid phase is totally winning this game of see-saw.

So the weight of the liquid phase can be calculated by:

And the weight of the solid phase can be calculated with:

 

And that should be all you need to know to understand Phase Diagrams!

Biomaterials: An Introduction to Materials Science – Material Defects

Material defects can be due to one of two causes: Chemical Impurities, or Physical imperfections.  Physical imperfections can be further broken down into the following

• Point Defects
  • Vacancy atoms
  • Interstitial atoms
  • Substitutional atoms
• Line Defects
  • Dislocations
• Area Defects
  • Grain Boundaries

Area Defects

When we talk about materials, we are generally referring exclusively to solids.  As engineers, we are expected to create these solids in specific shapes for specific applications.  To be able to mold and control the shape of the solids, engineers will solidify a molten material.  This happens in three steps.

1. nuclei form
2. crystals grow from the nuclei
3. the crystals grow until they meet each other; forming the grain structure

Grain structures can become problematic at grain boundaries.  A grain is defined as a domain of matter that has the same structure as a single crystal. 

Grain boundaries are where crystals of different orientations meet.  Note that grain boundaries are still single phase interfaces because the only difference between the two crystals are the orientations.

An example of an area defect is seen below:

 

We can see that each grain contains the same overall pattern and crystal structure.  However, they each meet at a different angle and orientation, thus causing gaps in the structure.

Line Defects

Line defects are the result of dislocations.  Dislocations are exactly as they sound, and are the result of atoms in the crystal structure being dislocated, from their (wait for it….) original location.

The classic analogy is: Imagine a stack of papers.  Now insert a half sheet of paper.  The resulting stack is dislocated from the point of insertion and half of the stack will be higher than the other half.

There are two types of dislocations: edge and screw.

Edge Dislocation

The classic analogy I described to you earlier (stack of paper) was actually an example of an edge dislocation.  It’s really self explanatory

Screw Dislocation

A screw dislocation will result in a screw formation of the planes of atoms.  It’s a lot harder to visualize, but the best way I can explain it is to imagine a slinky.  When the slinky is completely compressed, we can think of it as a simple cylinder.  If you stretch it a little, then all planes in the slinky will dislocate a little bit in a circular manner causing a spiral staircase, screw like thing.

So in the image above, a boundary of the material is “cut” and pushed downward.  That downward pushing causes a spiral just like in the slinky.  The point of “cut” is referred to as the screw dislocation.

Dislocation Density: the total dislocation length / unit volume.

Dislocation deformations whether from screw or edge result in slip.  Slip is any sort of plastic deformation corresponding to the motion of a dislocation in response to a shear stress.

The slip plane is the plane of dislocation.  In the diagram above the slip plane is the middle of the tetris block.  The slip direction is the direction of movement that results from the dislocation. 

Point Defects

Point defects can be any one of the following:

• vacancy atoms
• interstitial atoms
• substitutional atoms

Vacancy Atoms

Vacancy atom point defects are due to a missing atom.  The planes of atoms surrounding the vacancy deform due to things like creating the lowest entropy.

Interstitial Atoms

Interstitial atoms point defects are when an atom inserts itself into the crystal structure of a material, and disrupts the structure.

Substitutional Atoms

A substituational point defect is due to an atom of a crystal structure being replaced by a completely different type of atom.  Thus there is an impurity in the material.  This different composition may result in a completely different structure.

Biomaterials: An Introduction to Materials Science – Material Properties

Hello again everyone.  Isn’t this fun?  Isn’t this just spectacularly magnificent?  Nope.  Memorizing all of this is boring, but we have to do it to get to the fun stuff.  Trust me when I say that it’s a lot easier for you to read all this than for me to type all this.

Anyways.

We are going to go over some important material properties.  They are:

• viscosity
• viscoelasticity
• creep
• stress relaxation
• brittleness
• ductility
• resilience
• hardness
• toughness

 

Viscosity:

the resistance of a fluid to deformation under shear stress

A simpler way of understanding viscosity is that the higher the viscosity, the “thicker” it is, and the less easily it will flow.

 

The above equation relates the shear stress to the shear strain wile taking into account a viscosity n.  When n < 1, the fluid is a pseudoplastic and we observe shear thinning.  When n > 1, the fluid is dilatent and we observe shear thickening.  If n=1 the fluid is referred to as a Newtonian fluid.  An example of a Newtonian fluid is water.

Looking at the equation, we see that there is no direct proportionality between the stress or shear and the viscosity. Rather, viscosity is directly proportional to the shear rate.

For a pseudoplastic, I mentioned that we observe shear thinning.  The phrase itself describes a situation where the fluid thins out with an increasing shear force.  As the shear rate increases, the viscosity decreases, because n<1 and thus the fluid appears “thinner” and easier to flow through a volume.

The opposite is true for dilatent fluids.  With shear thickening, we can see that as we increase the shear rate, the viscosity becomes exponentially higher.  This ultimately increases the entire right side of the equation and causes the need for greater increases in shear stress to deform the fluid and get it to flow.

The higher the viscosity, the more resistant a fluid is to flow, and vice versa.

Viscoelasticity

the property of a material to demonstrate both viscous and elastic behavior while undergoing deformation

The figure above contrasts an elastic response to a viscous response to deformation.  The viscous response differs in that the shear stress will be applied, and then once removed the permanent deformation continues to occur.  What happens is that the shear stress will induce flow. So even after the stress is removed, flow continues.

The elastic response is reversible.  And thus, once the stress is removed, the strain reverts back to its original state as well.

Creep

time dependent permanent deformation to relieve stress under a constant load

 

Creep is the technical term to describe the physical phenomenon of getting “stretched out”.  For example, imagine a 5lb weight is being held by some sort of bar.  Initially, the extra force of the weight will pull down the bar and create an elastic response.  In this situation, the load changed from 0-5lbs. But after the bar has time to elastically adjust, there is still a deformation due to the constant 5lb load.  This deformation which is essentially “stretching” the bar out, is termed creep.

Stress Relaxation

the time decay of stress after a sudden deformation due to strain.

Whereas creep described the aftermath of strain on a material, stress relaxation describes the aftermath of stress  (well that’s an easy one!).  Note: stress relaxation refers specifically to viscoelastic materials.

If a material were elastic and followed Hooke’s Law then under a constant strain, the stress would stay constant as well.  But in viscoelastic materials, if a material is under a constant strain, the force required to maintain the deformation decreases with time and thus the stress decreases with time.

 

Brittleness

Brittle materials experience little or no plastic deformation.  They fracture quickly.

Ductility

a measure of the degree of plastic deformation upon fracture

Resilience

capacity to absorb and release energy during elastic deformation

The above shows us how to calculate the modulus of resilience.  Sigma is the stress and epsilon is the strain.  Essentially it is the area under the stress strain curve during elastic deformation.  Recall that

Toughness

capacity to absorb and release energy prior to fracture

Biomaterials: An Introduction to Materials Science – Stress vs. Strain

Two of the biggest concepts that one must intimately understand to understand materials science are stress and strain.

Stress is the normalized load applied to a material.  Stress is expressed as σ = F_n / A.  Stress is the force/area applied.

σ = F_n / A         (1)

where

σ = normal stress ((Pa) N/m², psi)

F_n = normal component force (N, lb_f)

A = area (m², in²)

Strain, similarly, is the normalized deformation that results due to a certain stress.

ε = dl / l_o = σ / E         (3)

where

dl = change of length (m, in)

l_o = initial length (m, in)

ε = unitless measure of engineering strain

E = Young's modulus (Modulus of Elasticity) (Pa, psi)

There are 3 types of principal loads: tension, compression, and shear.

 Tension/Compression involve situations where the area of the load is perpendicular to the loading direction and the change in length of the material is parallel to the original length.  Or put more simply, when the tensile stress is perpendicular to the length and the tensile strain is parallel we are dealing with either tension or compression.

Tensile stress will try to stretch the material whereas compressive stress will try to compress the material.

Shear Stress is a special type of stress that involves the applied load being parallel to the load area.  The strain will be in the same direction as the applied load.

The formula to calculate a shear stress is:

where

τ = the shear stress

F = the force applied

A = the cross sectional area

An example of shear stress is seen below:

 

Deformation

I’ve been using the term deformation to describe strain, but have yet to properly explain it.  Deformation is the change that results in the material after the application of a stress.  There are two types of deformation: plastic and elastic.  The difference is that elastic deformation is recoverable, while plastic deformation is permanent.  Think a rubber band stretching (elastic) vs. a glass breaking (plastic).

Stress Strain Curve

The most important diagram to understand the macroscopic properties of a material is probably the stress strain curve.  This is literally a graph of the stress on a material vs. the strain that results in the material.

So we see in the figure that stress is charted on the y-axis and strain is charted on the x-axis.  In my opinion, it’s rather odd because intuitively I would think the stress is the independent variable and the strain is the dependent variable.  But whatever.  Scientists way smarter than I set this up, so I will go with it.  (BTW, if you happen to know why the axes are as they are, do let me know in the comments!)

In this graph, 2 is the point where the material breaks.  And we can see that this will occur at a stress of 1.  1 is referred to as the tensile strength.  2 is referred to as the yield.

Stress vs. Strain Vocabulary

• Tensile Strength: the stress at which a material breaks or permanently deforms.  There are 3 types of tensile strength:
  • Yield strength: The stress at which a material changes from elastic to plastic deformation
  • Ultimate strength: The maximum stress a material can withstand. (max Y on the stress-strain curve)
  • Breaking strength: The stress coordinate on the strain-strain curve at the point of rupture (breaking)

In the figure above, point 4 is the tensile strength, 1 = ultimate strength, and either 2 0r 3 can be considered the yield strength.  The graph above is the stress strain curve for aluminum.  We see 2 general regions: a straight line region, and a curved line region.  The straight line region is the area under which the material is undergoing elastic (reversible) deformation.  The curved line region is representative of plastic deformation.

To be more “rigorous” (as a Professor of mine would love to say), point 2 is the offset yield strength.  This is due to a offset strain that is seen as the dotted line from point 5 to point 2.  Point 3 is then referred to as the Proportionality limit yield strength. All this bullocks is because yield strength can be defined in several ways.

• 1 = True elastic limit – the lowest stress at which dislocations in the material move.  This value is rarely used in engineering applications, but does provide some sort of chemical information
• 2 = Proportionality limit – up to this point, stress and strain are related by Hooke’s Law (defined below)
• 3 = Elastic limit – up to this point, the material only undergoes elastic deformation, past this is all plastic
• 4 = Offset Yield Strength – usually a value of 0.2% offset from the zero point.  Sometimes materials don’t even have a linear region, and the offset becomes very handy there.  It is helpful in making the stress-strain curves of different materials comparable

Hooke’s Law

Hooke’s Law is used to relate stress and strain through the Young’s Modulus.  If you didn’t notice, the “Hooke’s Law” title is gigantic. Yup, I did it on purpose.  Everyone note that Hooke’s Law is simultaneously important and fundamental and simple.

Most physics students first encounter Hooke’s Law through the equation F = – kx.  In words: the force equals the spring constant times the distance the spring is stretched or compressed.  The negative sign simply means that it is a “restorative” force.  So when you pull the spring and make the change in x positive, then the force is negative to pull it on the opposite direction.

So if we can describe elastic deformation with a force law used to describe springs then how should we visualize elastic deformation?  Like a spring, duh.  Silly.

There are two analogs to Hooke’s law for springs.  One for tension/compression and one for shear.

σ = Eε

The equation for Hooke’s Law for tension/compression.  Sigma equals the tensile stress.  E is Young’s Modulus (the analog to the spring constant) and epsilon is the tensile strain.

τ = G γ

The equation for Hooke’s Law for shear stress.  In words: Shear stress equals the shear strain times the shear modulus.

Young’s and Shear Modulus

The basic idea behind these two moduli is that the higher the modulus, the more resistive the material will be to the stress.  The higher the modulus, the higher the slope, thus there will be less of a strain for a given stress.

The Young’s and Shear Moduli are inherent macroscopic properties of a material.  Thus, they are often used to compare one material to another.

Poisson’s Ratio

Poisson’s Ratio is another thing that you just have to get familiar with before we dive into biomaterials.  Sorry y’all.

Poisson’s Ratio is the ratio of the lateral to the axial strain.

In the figure above, is the transverse strain, which is the same as the lateral strain.

Poisson’s Ratio is important because it relates the deformation in one plane to the deformation in another plan.  When you take a rubber band and stretch it, you should notice that the more you stretch it length wise, the thinner it becomes width wise.  It’s a very intuitive relationship.

Most materials will have a positive Poisson’s Ratio, meaning that an expansion in one direction will result in a compression in another.  The reason is that most materials will resist a change in volume more than they resist a change in shape. ( The Bulk Modulus K is generally higher than the Shear Modulus G)

And yes, in the rare case that the Poisson Ratio is negative, that implies that the material will actually get larger when stretched.  Some wine corks operate in this manner.  Therefore, when the cork needs to be reinserted into the bottle, when it is compressed (pushed in) the cork will become thinner allowing it to slide into the opening.  Once the compressive force is gone, then the cork should expand to complete close the opening.

Biomaterials: An Introduction to Materials Science – Classes of Materials

This is the ceremonious first post to The Bioengineer.  I’m going to get straight to the heart/purpose of this blog, which is trying to bestow upon you, all that I know as a Bioengineer.

As is clear by the title of this post, the first lesson is going to be about Biomaterials.  In these first few weeks we will be covering biomaterials, and various biological systems and how engineers are interacting with them.

What are biomaterials?

Essentially, biomaterials are materials that are constructed in order to interact with biology, and natural cells and tissues.  It should be clear why biomaterials are important.  The body has a very limited ability to self-generate.  We humans aren’t like eartworms.  Our cells are highly, highly differentiated and specialized.  Simple example: if we lose an arm, that baby is gone.

We can think of biomaterials as a special class and subset of the more inclusive category of “materials”.  Thus, before we start to understand the nuances of biomaterials in particular, we need to develop a broad-based understanding of materials science.

Introduction to Materials Science

There are 4 general classes of materials: metals, ceramics, polymers and composites.

1. Metals – large numbers of non-localized electrons; good conductors, non-transparent, strong but deformable.
2. Ceramics – oxides, nitrides, carbides; clay, cement, glass; insulating; often hard and brittle
3. Polymers – long-chain molecules; synthetic and natural; range of properties
4. Composites – combinations of materials; filler in matrix

The distinctly different properties of each class can largely be attributed to the differences in bonding.  Ceramics are composed of atoms connected through ionic and covalent bonding; Metals through metallic bonding; and Polymers through covalent & secondary bonding.

To understand the effects of bonding we have to get through some terminology first.  Ionic bonding is described as one atom donating a valence electron to another atom.  Through this process 2 neutral atoms become 2 oppositely charged ions.  These ions are then attracted to each other due to their opposite charge, and this attraction creates an ionic bond.

Covalent bonding is when two atoms share electrons. 

Metallic bonding is a special type of bonding.  There is no such thing as a metallic bond (the singular is reserved for ionic, covalent, and hydrogen).  Metals are unique in that they have so many electron shells that their valence electrons are very loosely held down by their nuclei.  The electrons are free to move from one atom to another.  Thus, when we have slab of metal, we can visualize it on a microscopic level as who knows how many metal ions floating in a sea of electrons.

There are also a couple of “properties of bonding” that we need to familiarize ourselves with to quantitatively describe the different types of bonds:

• Bond length: describes the length of the bond, usually in angstrums
• Bond energy: the energy required to homolytically cleave the bond so that each atom gets half the elextrons; or the energy of the intermolecular force (for secondary bonding)
• Melting temperature: The temperature at which a compound will transition from a solid to a liquid ( or from a crystalline to an amorphous state)
  • Essentially, the larger the bond energy the higher the melting temperature.  This is because temperature is related to thermal energy.
• Coefficient of Thermal Expansion: the fractional change in length per degree of temperature change
  • The logic: as a material increases in temperature, this energy is stored in the intermolecular bonds, causing the length of the bonds to increase.  So materials will generally expand in response to an increase in thermal energy.  Hence the name.
  • Alpha = coefficient of thermal expansion.  L=length of material.  L0 = orignal length of the material.  T = temperature.

Now that we understand various properties of bonding, let’s related them to the four classes of materials. (What are they again?) Don’t worry, I already forgot also.  But after having looked them up, the four classes of materials are: ceramics, metals, polymers and composites.  In this exercise we won’t consider composites, because the properties of composites are highly variable.  They can be composed of any mixture of the other three materials.

Ceramics

• High melting temperature
• large bonding energy
• small coefficient of thermal expansion
• moderate density

Ceramics are generally characterized by ionic and covalent bonding.  These types of bonds have high bond energies and melting points.  Thus, we see a high bond energy and melting temperature in ceramics.  Ceramics have a moderate density as their ions often have special requirements for bonding (fourfold coordination for covalent bonds and charge neutrality for ionic solids)

Metals

• moderate melting temperature
• moderate bonding energy
• moderate coefficient of thermal expansion
• high density

Metals are often the densest packed of the three due to the metallic bonding and the minimal restrictions.  Also, metals are generally composed of atoms later on in the periodic table, with large atomic masses. 

Polymers

• low melting temperature
• small bonding energy
• large coefficient of thermal expansion
• low density

Polymers have the lowest density of the three classes.  Although single polymer chains are composed of several covalent bonds, these chains are held together to form the polymer solid through secondary bonds.  Secondary bonds are the weakest interactions, and thus have the lowest bond energy and melting temperature.

A general rule of thumb is that the weaker the intermolecular interaction, the longer the length of that interaction.  For example, a triple-bond is much shorter than a single-bond.  And accordingly, the polymer chains are kept at a further distance from each other by these secondary bonds than atoms are in metals and ceramics.