Laser machined poles:

1. Pole Plate Fabrication for the 3DFM CISMM: Computer Integrated Systems for Microscopy and Manipulation Background Review of pole plate fabrication techniques Laser machined poles: The combination of a small laser spot (10 to 20 microns in diameter) and intense short laser pulses allows this process to generate cuts with accuracy up to ±5 microns. We have begun testing a variety of pole configurations (3 pole, 6 pole, comb structure) made using this technique with materials of various thickness and magnetic properties. These poles are then plated on cover-slips for use in the 3DFM. Materials currently being tested are below: The 3DFM requires pole pieces with high permeability, high saturation moment, low hysteresis moment and small thickness for the limited spaces. Based on different geometry designs, we use thin film permalloy (Ni:Fe=80:20) making 3DFM pole plates for varied applications like single bead moving or multi-bead magnetic separation. Photolithography patterned, electrodeposited poles: A B C E D Poles design for 3DFM Starting from glass cover slice, A: thermal deposit 40 nm Cu; B: spin-coat 2 layer of AZP*4620; C: UV photolithography; D: electrodeposit 20-30 μm permalloy; E: etch away AZP and Cu, to get poles. Left: 3DFM diagram of objective with pole plates. Below: Drawing of pole plates with different applications. We use thick photoresist AZP 4620 as a template then do the electrodeposit inside this template area. By controlling how many coulombs run through the electrode, the chemistry in the plating bath, and plating parameters, we can fabricate poles with specific alloy components and thicknesses. Techniques based on Su-8 photoresist are also available. *AZP 4620 is a commercial available positive photoresist. We also use some negative photoresist like Su 8 to do the relatively same process. Normally this method can support depth as high as 100 micron pole pieces. Poles Flow cell Top,design for multi-beads control; bottom, tip end area Poles combined with flow-cell for magnetic separation Drawing of laser machined pole plate Poles measurements and characterization Photolithography patterned, electrodeposited poles: Laser machined poles: The soft magnetic properties of the pole materials are important for manipulating particles through complex magnetic fields. Permalloys with Ni:Fe = 80:20 are yield high field gradients for nano-scaled particle manipulation. Based on the poles fabricated by both electrodeposition and laser machining, we plan to systematically study how the poles’ geometry effects our manipulation ability. The different designs will be used for diverse applications ranging from rheology study to bio-separation. Preliminary data shows we can get 900 pN from a 4.5 micron bead using poles made by plating. While some of the laser machined poles can get over 5 nN under the same situation. Three pole design Four pole design 200 um 100 um 1000 um Laser machined 3 pole configuration. Element Line Weight% K-Ratio Cnts/s Atomic% --------------------------------------------------------- Fe Ka 20.76 0.2407 149.70 21.60 Ni Ka 79.24 0.7809 307.55 78.40 Total 100.00 500 um EDX data of the plated material which is permalloy with Composition Ni:Fe = 80:20. SQUID Magnetometer data (high saturation moment 0.84 T, hysteresis moment near 100 G). A typical soft-magnetic material. Laser machined comb structure http://cs.unc.edu/Research/nano/cismm/3d/index.html Collaborators:Collaborators: Dr.Brian Stoner (MCNC) Project Lead: Dr. Richard Superfine Investigators: Jing Hao, Jay K Fisher, Leandra Vicci, Deborah Sill 11,21,2003