Well, that's a first. I don't usually answer questions here on Clarity.fm with my electrical engineer hat on.

Shielding materials vary depending on the frequency distribution of EM waves emanating from the source. The same medium will have a greater or lesser attenuating effect for high and low frequencies – e.g. microwaves and radio waves. Also, energy will dissipate across distance even in a vacuum.

The government uses more robust computers that are insulated against electromagnetic leakage, since keyboard signals can be externally tapped, giving away passwords.

Plastics are used. So is copper mesh for RF shielding – though not for microwave frequencies. The range of suitable materials is actually quite extensive, and multiple substances may need to be utilized in combination, depending on the frequency distribution. Thickness is a factor as well, obviously.

Hire an electrical engineering student to evaluate the frequency spectrum emanating from your target devices. The student ought to be able to suggest materials and design shielding to reduce energy levels below any desired threshold.

One of my professors was involved with mathematical simulations of EM penetration into child brains during the early days of cell phones. (Kids have less shielding, since their ears and skull are smaller. SWell, that's a first. I don't usually answer questions here on Clarity.fm with my electrical engineer hat on.

Shielding materials vary depending on the frequency distribution of EM waves emanating from the source. The same medium will have a greater or lesser attenuating effect for high and low frequencies – e.g. microwaves and radio waves. Also, energy will dissipate across distance even in a vacuum.

The government uses more robust computers that are insulated against electromagnetic leakage, since keyboard signals can be externally tapped, giving away passwords.

Plastics are used. So is copper mesh for RF shielding – though not for microwave frequencies. The range of suitable materials is actually quite extensive, and multiple substances may need to be utilized in combination, depending on the frequency distribution. Thickness is a factor as well, obviously.

Hire an electrical engineering student to evaluate the frequency spectrum emanating from your target devices. The student ought to be able to suggest materials and design shielding to reduce energy levels below any desired threshold.

One of my professors was involved with mathematical simulations of EM penetration into child brains during the early days of cell phones. (Kids have less shielding, since their ears and skull are smaller. So the industry standards are based on such small heads as the limiting case.)

thanks a million for your answer. I am not an expert in the field so I think I didn't understand it totally or maybe the question is bad formulated. I am asking specifically for the waves emited by laptops and/or smartphones, not microwaves or radio.
I want to know if specific materials such as copper, nickel and silver are right shields for that kind of EMR.

A Faraday Cage (http://en.wikipedia.org/wiki/Faraday_cage) blocks electromagnetic waves from passing through it. A Microwave uses this concept (to stop said micro waves from hitting the user), and aluminium foil has also been used as a shield (hence the gag with conspiracy theorists wearing them as helmets). I have a background in robotics and mechatronics engineering and can go into greater detail or assist you in designing a product which could incorporate such a shield if you would like to give me a call. A while ago, I was researching the difficulty of extracting data from RFID cards and found it incredibly easy. Thus, I think such a shield could have quite a few valuable applications.

Please search "Electromagnetic shielding" on Wikipedia. This should help you get started.

Best of luck,
Jim