Dear Mark,

    It is useless to make the coil bigger. The coil is a composition of turns. The flux density in the center of the turn is
B = mu0 * I / 2R, where R is the radius of the turn.
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/curloo.html
    The only way to increase the flux density is to increase the current value. So I keep the coil size the same as original 5T-coil and increase the current by 40%.

    The B*dB product is -4.6. It was -14.7 for the 5T-coils located 10 cm away. So the force is only 30%.

    Time spent 1 hour.

	
	
	
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Dear Mark,

    QuickField can plot the energy density color map, that is (B*dB/mu0) =
= 8e6 * B * dB [J/m3]
    
    Form our experiments (Aug 23) we get the simple equation to compute the force acting on a 100-nm particle, that is
Force = 1.2e-15 * B * dB [N]

    Putting these two together we get the equation to compute the force from enery:
Force = 1.5e-22 * Energy [N]

    100-nm particle weight was estimated as 4.57e-17 N. Putting this value in the equation above we can estimate the required magnetic field energy density that is capable of lifting the particle:
4.57e-17 = 1.5e-22 * Energy_
Energy = 305 kJ.

    I made the color plot of the force/weight ratio. Please see attached. Should I do the same for the 5T coils? For the 200-nm particle?

    It took 0.5 hour.