A blog about anything nanotech

Carbon nanotubes not doing it, try graphene

System Administrator Sunday 23 of May, 2010
Graphene was discovered by Andre Geim. This new material has the following properties:
  • Monolayer of a single carbon atoms forming a 2D structure (think chick wire in shape) but this is the thinnest material imaginable.
  • Strongest material ever measured
  • Stiffest material
  • Stretchiest crystal material
  • Highest thermal conductivity
  • Highest intrinsic mobility
  • Ballistic electrical conductivity
  • Longest mean free path at room temperature
  • Most impermeable (ever to hydrogen)

Physical Reference data

System Administrator Sunday 23 of May, 2010
The constants and SI unit data is just the tip of the data treasure trove at NIST. NIST also has databases of physical reference data on any element or molecule you might imagine from properties of elements to spectra to nuclear data, oh my.

Cancer and theoretical sciences

System Administrator Saturday 17 of April, 2010
I'm stunned to find out how little we know about cancer after attending the Understanding Cancer via the Theoretical Sciences at Princeton University on Thursday. The list of things we don't know about cancer appears to be fundamental and includes
  • Basic material properties of biomaterials
  • Ability to measure basic properties and forces over various length scales
  • Understand the energy budget associated with cancer
  • Understand the physics of the disease
  • Understand the emergent behavior of cancer
The complexity of cancer is challenging to understand and the statistics are grim
  • 1 in 3 people will get cancer
  • 2009 spending on health care was $2.5T or 18% of the US economy
  • Health care spending projected to be $4.4T by 2020
  • 10.3 million people projected to die from cancer by 2020
  • 2.3 million people/year projected to be diagnosed with cancer in 2030; That's 17 million people/year world wide
  • The type of cancer you get depends where you live with the US having some of the highest rates
  • Cancer depends on your genome and epigenome
    • people in other countries that move to the US have the same cancer rates after one generation
We understand parts of the this complex system but not the parts that allow us to control the disease. The National Cancer Institute has be some new and promising initiatives to help understand the disease with the goal of developing techniques to control the disease. Some of these initiatives include
  • Better imaging techniques to measure across many length scales from the cell to the organ.
  • Cancer Genome Atlas
  • Using Physics to model the biology
  • Nanotechnology Alliance for Cancer
The thought is that Physics + Nanotechnology + Imaging will lead to a better understanding of cancer that can be used to develop more effective treatments to control cancer.

Nanophotonics and the Lorentz Oscillator Model

System Administrator Thursday 08 of April, 2010
The behavior of an nanophotonic material can be analyzed using the simple Lorentz oscillator model of an electron bound to the nucleus of an atom by a spring1 . The spring is defined by its spring constant (C) which describes the restorative force associated with the spring (Hooks Law) and the damping factor the spring exhibits. In the figure below, the electron is a radius r from the nucleus and a dipole moment exists between the electron and nucleus that is equal to the charge of the electron times the radius. The electric field of the photon excites the system causing it to oscillate. F=ma is used to describe the system. The properties of the material will determine the susceptibility of the system to the e-field and determine the spring and damping constants.

Lorentz Osc Model

1 Figure and description adapted from the course ECE 695s Nanophotonics taught by Vladimir M. Shalaev.

Energy cost per kWh

System Administrator Thursday 08 of April, 2010
Using last months gas and electric bills, I've calculated that at an average kWh for March 2010 costs
  • $0.046/kWh from natural gas, and
  • $0.176/kWh from the electric company.
I was thinking that it would cool to replace my existing furnace with a Solid Oxide Fuel Cell (SOFC) like the one based on Bloom Energy but the waste heat could be used to heat hot water in an indirect hot water heater, and provide base board hot water heat. The Bloom system appears to be 51.6% efficient so that would make the electricity costs around $0.092/kWh. The system would need to provide about 20 kW of output power.

Work, work, work

System Administrator Saturday 03 of April, 2010
It's all come down to work and what is becoming our favorite measure of work, the Joule. Work is defined as force times distance or how much energy it takes to move a object a certain distance1 . It has units of Newton*Meters or Joules. We define volt as the amount of work it takes to move a charge through an electric field. Thus, 1 Volt = 1 Joule/Coulomb2 . Power is defined as the rate of work of over time3 . Power has units of Watts or Joules per second.

I did not think much about this until I got this nifty little energy harvester module. A look at last months electric bill showed that we average about 17 kWH per day. That's 61.2 Million Joules! This does not include the gas furnace that consumes 809.8 Million Joules on average per day. Yikes. My energy harvester module comes in two version: Model EH300 at 4.6 milliJoules and EH300A at 30 mJ. There are like nine orders of magnitude between my daily electricity consumption and the storage capability of my energy harvesting module. That's a factor of a billion!

I looked at the battery in my cell phone which is rated at 820 mAh or 3 WH. This translates to 10.9 kiloJoules. 5 orders of magnitude more than my energy harvester. D'oh. This seems to indicate that designing nanostructures to harvest meaningful amounts of energy will be challenging and the electronics associated with such systems will need to be rethought to use far far less energy than they do today. To see more about the modules, check out my Electronics blog Energy harvesting modules.

Work Diagram

1 Physics by Halliday & Resnick, ©1978, p117.
2 Physics by Halliday & Resnick, ©1978, p622.
3 Physics by Halliday & Resnick, ©1978, p127.

Nanosensor system architecture

System Administrator Sunday 28 of March, 2010
I've been thinking about building a nanosensor system based on the architecture shown below. Nanosensors or nanobiosensors are designed and selected for a particular application to detect the pesence and amount of a variety of substances that could include:
  • Biotoxins like salmonella or E.coli
  • Biomarkers like PSA and similar proteins associated with breast, lung, and ovarian cancer
  • Chemicals
  • Explosives
  • Humans and animals for search and rescue
This could be individual nanosensors or arrays of sensors. The nanobiosensors would have a bioreceptor that is attached to a transducer by a linker molecule. The transducer could be a SAW, nanowires, microbalance, cantilever, or FET to name a few. These transducers all have different electrical interfaces an require a unique analog interface and analog signal processing. Once the output of the transducer is conditioned, digital signal processing can be applied to provide response times that are not possible with a low power microprocessor. The microprocessor provides overall control and communication of the nanosensor system.

This system could be attached to a robotic platform to allow the nanosensor system to be mobile. Armies of the robotic nanosensor systems could be unleashed for search and rescue,to locate toxins, or to locate resources (molecules with possible medical benefits in a jungle perhaps). With wireless communication the robotic nanosensor system could be relay data across all sensors to form a quantitative picture of the toxins in a region. GPS could be included in the system to provide accurate position information.

Nano Sensor System Diag

Even at the nanoscale we wonder if our wires are making good contact

System Administrator Tuesday 23 of March, 2010
Making good electrical connections to devices has always been important but may be even more important with organic semiconductors. The high simplified figure below shows a hypothetical single organic molecule (polyacetylene) based FET with metal contacts at each end. According the the article Molecular electronics with single molecules in solid-state devices by Kasper Moth-Poulsen & Thomas Bjørnholm, the molecular-electrode coupling strength strongly effects the electronic state of the entire device. The conduction of the electrons through the device can range from hopping to tunneling as the molecule-electrode contact goes from weak to strong.

Polyacetylene Contacts