Patent ID: 7210843

Claim:
A method for mixing a fluid sample, comprising the steps of: (a) providing a multidirectional shaker comprising a base; a first wall extending upwardly from said base; a first electromagnetic drive unit lacking a permanent magnet and comprising a first housing affixed to said first wall, a first core assembly within said first housing, a first coil surrounding said first core assembly, and a first armature assembly adjacent said first core assembly and configured for displacement toward and away from said first core assembly, said first armature assembly operatively engaging a first support platform so as to move said first support platform in a first substantially horizontal direction; at least one first spring member between said first wall and said first support platform positioned to move said first support platform in a second direction opposite said first direction; a second wall extending upwardly from said first support platform; a second electromagnetic drive unit lacking a permanent magnet and comprising a second housing affixed to said second wall, a second core assembly within said second housing, a second coil surrounding said second core assembly, and a second armature assembly adjacent said second core assembly and configured for displacement toward and away from said second core assembly, said second armature assembly operatively engaging a second support platform so as to move said second support platform in a third direction; and at least one second spring member between said first support platform and said second support platform positioned to move said second support platform in a fourth direction opposite said third direction; (b) connecting said multidirectional shaker to a power supply supplying a drive signal at a fixed drive signal frequency, wherein said at least one first spring member and said at least one second spring member further comprise spring members having spring constants that cause a natural frequency of said multidirectional shaker to approximate said fixed drive signal frequency; (c) positioning a fluid sample on said second support platform; (d) supplying said drive signal to said first and second coils to respectively magnetize said first and second core assemblies to respectively attract said first and second armature assemblies to said first and second core assemblies, and to respectively move said first and second support platforms in said first and third directions; (e) terminating said drive signal to cause said at least one first spring member and said at least one second spring member to respectively move said first and second support platforms in said second and fourth directions; and (f) repeating steps d and e to mix said fluid sample.