Affinity -Advanced Micro-Electro-Mechanical Systems (MEMS)
Utilizing advanced micro-electro-mechanical systems (MEMS) fabrication methods, a fluidic microchannel is embedded inside the silicon resonator. Figure 1. By suspending the silicon lever in vacuum and embedding the micro-fluidic channel within it, LifeScale is able to exploit the high Q of a vacuum system whilst at the same time allowing microbes suspended in fluid to pass through the resonator. In this way biological samples, such as living microbes, can be measured under physiological conditions. To measure a microbe, the change in resonant frequency of the sensor is monitored as the microbe passes along the micro-channel resonator from position 1 to 3, Figure 1.
As the microbe enters the channel, position 1, the effect of the added mass can be seen in the frequency data. The maximum frequency shift occurs when the microbe is at the tip of the resonator, position 2, and is proportional to the microbe’s buoyant mass, i.e. the mass of the microbe over that of the fluid it displaces. As the microbe leaves the channel, the measured frequency returns to that of the baseline resonant frequency, position 3.
By measuring the duration of the excursion from the resonance frequency, position 1 to 3, it is possible to calculate the microbe’s transit time through the sensor, Figure 2. As the geometry of the sensor is precisely known, the transit time of individual microbes can be used to determine the total volume of inoculate passing through the sensor in a given time. By simply counting individual microbes as they pass through the sensor and calculating their velocity, an accurate measure of the microbe concentration in counts per ml is obtained.