Deterministic ratchet for sub-micrometer bioparticle separation

A method for separating sub-micrometer sized bioparticles, the method comprising:

• depositing a fluidic sample in a microfluidic channel, wherein a plurality of micro-posts are disposed within the microfluidic channel;
• and
• applying an electric field gradient to the fluidic sample to induce transport of sub-micrometer sized bioparticles in the fluidic sample by
• applying a first waveform to the fluidic sample in the microfluidic channel, wherein the first waveform is a square wave having an amplitude, a frequency, and a DC offset voltage, and
• applying a second waveform superimposed on the first waveform only during one selected from a group consisting of a high period of the first waveform and a low period of the first waveform, wherein the second waveform is a sinusoidal wave with a higher frequency than the first waveform, and wherein application of the second waveform superimposed on the first waveform causes the sub-micrometer sized bioparticles to separate by size.

A method of separating sub-micrometer bioparticles by size utilizing ratchet migration using a system including

• a microfluidic channel,
• a structure configured within the microfluidic channel, the structure comprising an array with rows, the array including posts arranged in the rows, wherein some rows in the array are shifted in a lateral direction relative to other rows in the array,
• a reservoir disposed at each of two opposite ends of the microfluidic channel, and
• an electrode positioned in each of the reservoirs,
• the method comprising:
• introducing a fluid into the microfluidic channel, the fluid containing the sub-micrometer bioparticles, wherein the introduced fluid immerses the electrodes;
• and
• applying a biased alternating electrical potential via the electrodes in each of the reservoirs, the biased alternating electrical potential comprising
• a first waveform with a first frequency that induces electro-kinetic flow of sub-micrometer bioparticles in the microfluidic channel alternatingly in a first direction during a high period of the first waveform and in a second direction during a low period of the first waveform, and
• a second waveform with a second higher frequency superimposed on the first waveform only during one selected from a group consisting of the high period of the first waveform and the low period of the first waveform, wherein the second waveform selectively induces a dielectrophoretic trapping force to selectively restrict migration of larger sized bioparticles during application of the second waveform,
• wherein applying the biased alternating electrical potential causes bioparticles of a first size to migrate towards a first reservoir at a first end of the microfluidic channel and causes bioparticles of a second larger size to migrate towards a second reservoir at a second opposite end of the microfluidic channel.