Ceramic piezo disks array construction - materials and methods

[akis]

I have constructed an array of 9 ceramic disks in 3 groups of 3 and on an area of about 100mm x 65mm. I have attached a picture of how they are arranged. The surrounding rectangle is the size of the whole pad around 130mm x 90mm.

The array will be placed on a curved surface, the curvature varying from application to application so the array is semi-flexible.

Currently the 9 disks are held together by silk tape and on top another fixing tape. The glue present on the silk tape holds the disks in place relative to each other. The fixing tape then secures the whole array onto the target surface.

Because the target surface is curved and because the arrays are washed in water after each application, the assembly loses a bit of its shape, but most importantly the glue leaks and the whole thing becomes rigid with glue and not very supple anymore. Therefore after a few use-wash-dry cycles, the assembly must be taken apart, the silk and other tapes discarded, and the ceramic tiles then reused.

I was thinking of providing a better construction using a thin plastic holder/template to glue the ceramic disks permanently onto it, so that they could be washed in water without losing their shape. I could cut the plastic template out of some plastic sheet. I was thinking maybe 1mm thickness, must be flexible but also strong. I attach another picture of what the plastic holder might look like.

So what remains is (a) identification of the correct plastic and (b) cutting it perfectly - cannot imagine trying to cut this template out of a plastic sheet with plain old sciscors.

Any ideas greatly appreciated. I have attached a picture of the proposed plastic holder.

[moffy]

Polyethylene or Mylar, both very tough and tear resistant. The Mylar might be hard to cut though, and expensive, also hard to glue to. Not sure how you would cut them, maybe a hot wire and use a paper template?
Where did you get your piezo disks from? I would love to get some flat piezo material and maybe experiment with piezo transformers, but so far the prices I've seen seem excessive.

[akis]

I spoke to a plastics company and the lady suggested HDPE Natural, Polypropylene, and Nylon 6. I have ordered sheets of 1mm, 1.5mm and 2mm thickness to cut out rough templates and try for flex and retaining shape.

Actually for the properties I need, I am thinking, a thin sheet of steel would do the job, thin enough to flex over a football and strong enough to maintain its structural shape and flex back when removed from the football. Maybe 0.2 thickness? Maybe less. But how would I find such a sheet and who would cut the shapes for me?

[moffy]

I spoke to a plastics company and the lady suggested HDPE Natural, Polypropylene, and Nylon 6. I have ordered sheets of 1mm, 1.5mm and 2mm thickness to cut out rough templates and try for flex and retaining shape.

Actually for the properties I need, I am thinking, a thin sheet of steel would do the job, thin enough to flex over a football and strong enough to maintain its structural shape and flex back when removed from the football. Maybe 0.2 thickness? Maybe less. But how would I find such a sheet and who would cut the shapes for me?

The pcb manufacturers make stainless steel templates if you desire.

[akis]

I am afraid I made a mistake ordering all those plastic sheet samples at 1mm and 2mm thickness, this is too thick. We will see.

In the mean time what would you think of mica as used for heatsink insulators? It is 0.1mm thin and I think unless you try to flex it something silly it would not crack and at 0.1mm it is already quite rigid but still can be cut with home tools if needed, unlike steel. Who would be selling mica sheets for me to try...

[akis]

Many thanks for the comment.

In terms of choosing an appropriate material, the "thinner plastics" (like disposal or carrier bags) are not rigid to maintain a pattern's shape and relative structure. They are hardly more rigid than a piece of thin cloth.

A (thin) aluminium or copper foil (thicker than "kitchen foil" of course) does not flex but bends and never goes back to its original shape.

Maybe a foil of brass might be strong and flexible.

I have the plastic samples arrived today, for sure the 1.5mm and 2mm are way too thick to be of use. Will try the thinner ones and let you know.

[akis]

I have received sample plastics HDPE, Nylon 6 and Polypropylene - the thinner sheet is 1.0mm. Unfortunately 1mm is way too thick to be of any use. I will ask them today if they can do thinner.

[ruffy91]

Try inkjet transparencies. You can print the template to it and the rough side is good to glue on. Also they're about 0.125mm thick, flexible but retaining their shape.

[akis]

I think I need something slightly, ever so, tougher than a transparency. But I could use 3-4 sheets together somehow.