Fast Detection of Biomolecules in Diffusion-Limited Regime Using Micromechanical Pillars

Abstract

We have developed a micromechanical sensor based on vertically oriented oscillating beams, in which contrary to what is normally done (for example with oscillating cantilevers) the sensitive area is located at the free end of the oscillator. In the micropillar geometry used here, analyte adsorption is confined only to the tip of the micropillar, thus reducing the volume from which the analyte molecules must diffuse to saturate the surface to a sphere of radius more than 2 orders of magnitude smaller than the corresponding linear distance valid for adsorption on a macroscopic surface. Hence the absorption rate is 3 orders of magnitude faster than on a typical 200 × 20 square micrometer cantilever. Pillar oscillations are detected by means of an optical lever method, but the geometry is suitable for multiplexing with compact integrated detection. We demonstrate our technology by investigating the formation of a single-strand DNA self-assembled monolayer (SAM) consisting of less than 10(6) DNA molecules and by measuring their hybridization efficiency. We show that the binding rate is 1000 times faster than on a "macroscopic" surface. We also show that the hybridization of a SAM of maximum density DNA is 40% or 4 times the value reported in the literature. These results suggest that the lower values previously reported in the literature can be attributed to incomplete saturation of the surface due to the slower adsorption rate on the "macroscopic" surfaces used.

Biosensors based on nanomechanical systems

“…The vibration plane is parallel to the liquid/air interface and the beam is resonating in air thus the quality factor is not degraded by viscous damping and drag of the fluid on the largest section of the resonator. See references [131][132] Micropillar resonators. Contrarily to the widespread fabrication of the nanomechanical resonators parallel to substrate or chip, micropillars are vertically oriented [131][132] .…”

“…See references [131][132] Micropillar resonators. Contrarily to the widespread fabrication of the nanomechanical resonators parallel to substrate or chip, micropillars are vertically oriented [131][132] . Tailoring the arrangement of micropillar arrays the surface can be transformed in superhydrophobic with large contact angles of up to 150 degrees.…”

“…Since the vibration plane is parallel to the liquid-air interface, as it occurs with quartz crystal microbalance, the micropillar exhibits high quality factors of 500 in liquid. DNA hybridization has been followed in real-time with micropillar resonators without the need of labels at 10 nM target concentration 132 .…”

High Performance Three‐Dimensional Chemical Sensor Platform Using Reduced Graphene Oxide Formed on High Aspect‐Ratio Micro‐Pillars

“…However, emission of harmful byproducts and pollutants, such as nitrogen oxides (NO x ), carbon oxides (CO x ), sulfur oxides (SO x ), ammonia (NH 3 ) and so on, have also increased signifi cantly and endangered our health and environment over the long term. To monitor chemical materials exhibited many interesting advantages, such as increasing surface-to-volume ratio, mass transport, reactive site density over a specifi c device area, [ 26,27 ] for supercapacitor [ 28,29 ] and other electrochemical applications.…”

Role of Nanotechnology in Cancer Diagnostics

“…A forerunner is the glucose biosensor that has been widely used to measure glucose at home in diabetic patients. Mass sensitive transducer quartz crystal microbalances have also been applied for cancer biomarker detection and a very recent pillar technology is developing with the promise of being a rapid test with a very high sensitivity [12]. In the near future, we will be able to measure biomarker concentrations on a device such as a smart phone as is exemplified in the lab-onchip SmartBioPhone device, which can be used in four point of care applications: environmental, food, cancer, and drug monitoring [13].…”