MLINE for Control Channel Routing

After installing AutoCAD 2012 today I came across the MLINE command. It is an easy way to draw a set of parallel lines that follow a path.  Steps:

1. MLINE at the command prompt
2. Enter J to choose justification - Zero seems most appropriate: centers the path taken between the lines drawn.
3. Default scale is 1, which is 1:1 with the current drawing units.  Set this to be the width of your control channel.
4. Start tracing a path point by point.
5. When finished hit ESC.

Voila! A neatly drawn channel without "rectangle madness".  So that it will print you'll need to convert the MLINE to a PLINE.  For that you can:

1. EXPLODE the MLINE you've just drawn
2. Use PEDIT to Join all the resultant line segments

This could get quite laborious for a long channel with multiple turns.  So instead you can use a great AutoLISP script created by Lee Mac over at CADTutor:

(defun c:m2p (/ vlst ovar ent ss elast)
  (setq vlst '("CMDECHO" "PEDITACCEPT")
    ovar (mapcar 'getvar vlst))
  (if (and (setq ent (car (entsel "\nSelect Multi-Line...")))
       (eq "MLINE" (cdadr (entget ent))))
    (progn
      (mapcar 'setvar vlst '(0 1))
      (command "_explode" ent) (setq ss (ssadd))
      (mapcar '(lambda (x) (ssadd x ss)) (Ent_List_to_End ent))
      (setq elast (entlast))
      (command "_pedit" "_M" ent ss elast "" "_J" "" ""))
    (princ "\n No Multi-Line Selected "))
  (mapcar 'setvar vlst ovar)
  (princ))

(defun Ent_List_to_End(ent / a)
  (reverse
    (if(setq a(entnext ent))
       (cons ent(Ent_List_to_End a)))))

Breathing moisture barrier film and bottom-less plates

(More stuff out of my "ideas" Google Doc)

ACLAR film:
Typically used for embedding histology sections.  Fluorcarbon based, clear as glass, flexible, and easy to cut - I'm assuming doesn't produce shards. According to the specs, it has a high O2 permeability, but low to nill moisture transmission.

Potentially useful for a number of things:

• a way to get around special rehydration channels or fluorinert in valve lines in PDMS based microfluidics
• top
• thick casting for structural support
• aclar film
• control layer (thin)
• flow layer (thin)
• glass slide/coverslip
• bottom
• a lid for microplate readers - I wonder if they make the stuff with adhesive backing.

Greiner Bio-One makes bottom less plates now!

These would be useful if the LED tray experiments get started again - no need to custom manufacture the base plate.

These might also be useful for more standardized microfluidic assembly - e.g. select a large bottomless well plate (6-well). Glue a chip (glass and all) to one of the wells from the bottom.

Milli (Vanilli) Fluidics - Part 2

4% agarose in PBS (200 g/L salinity, pH 7.2)

The idea has been refined:

• Make two adjacent channels with a weir in between
• Cells get caught in the weir as flow moves in from one channel, over the weir, and out the other channel
• Same flow path is used for adding stimulant

Making grooves
Attempt 1
Used two fine gauge wires covered in tape.  Found some wire in the common tool area, from the looks of it, it was 30awg.  The wires provided the depth for the channels while the tape smoothed out the profile and made the weir in between the wires/channels.

The wires were positioned so that neither channel extended completely across the pad region, but with a small (~5-10mm) of overlapping region for the weir.

Wire+tape 'mold' was assembled on a regular office grade transparency sheet to make release of the mold from the agarose pad easier.

Result
Channels made this way were really really deep.  The pad patterned was also too small.  so channels went all the way across.  Didn't test loading with cells.  Regular Scotch tape (matte finish) produced a lot of observable roughness in the resultant patterned pad.  Prefer it to be smooth.

Attempt 2
Instead of wire, used strips of tape, covered in tape.  Much easier to position.  Used clear packing tape as the 'smoothing' layer.

Result
Grooves pattern probably caused by scratches from tweezers used to smooth out air bubbles.  Cells get caught in these grooves.  Cells dropped onto the pad (5uL) before coverslip.  Trapping in the weir doesn't seem robust.

Attempt 3 
Discontinuous single channel patterned using wires heavily smoothed with tape.

Result
Attempted cell loading via channel.  Appears that there is enough non-uniformity (non-flatness) in the pad that promotes bulk capillary action across the entire pad.

Attempt 4
Fine grit sand paper roughened packing tape.  Sandpaper drawn over surface once with moderate pressure, to create deep parallel grooves (will result in channel walls on pad).

Result
The pattern was evident when the pad was dry, but once wetted, it was not observable.  Only 2uL of cells spotted (small pad).  Cells in center popped - probably from over pressure of coverslip.

Todo: Attempt 5
PDMS 'mold box'.  Put a small transparency film roughened with sandpaper on a flat surface.  Outline the film with tape, approx 2-5mm from the film edge.  Cast PDMS over the top of this.

The PDMS will be come a small molding box to create a pad the size of the transparancy film with grooves from the sandpaper roughened area.  Drop this box over a spot of molten agarose on a glass slide.  Cool the assembly and peel away (hopefully with the agarose portion still stuck to the glass slide).

Milli (Vanilli) Fluidics

I'm working on some experiments with algae (while we rush to publication - lest we get scooped - ugh!) that require quickly isolating a few and stimulating them with a grab bag of chemicals.  I have microfluidic devices specifically designed for other purposes, but shoe horning them into this experiment will probably be a project in and of itself.

I've made "poorman's" microfluidics by cutting pieces of scotch tape on glass slides and casting PDMS against it. However, the cells I'm working with are small and motile enough to make anything created this way totally inadequate.  Besides, I'm a bit worried that the random organics in PDMS (and Scotch tape adhesive) can throw off my cellular response.

So here's what I want to test - an agar/agarose pad with a groove patterned it in connected to a Laplace pressure pump.  More specifics:

• I can make a dozen of these pads (at least ones without a groove) in about an hour
• To make the groove I need to pattern the slide I use to 'flatten' the pad
• The Laplace pump will be made with a coverslip with a tiny hole in it that:
• I place a drop of stimulant over
• will be far away from where I image cells
• needs to be aligned to the groove in the pad

Will this work?  Off to the drawing board!