Resonant-cantilever bio/chemical sensors with an integrated heater for both resonance exciting optimization and sensing repeatability enhancement

Abstract

With an integrated resonance exciting heater and a self-sensing piezoresistor, resonant micro-cantilever bio/chemical sensors are optimally designed and fabricated by micromachining techniques. This study is emphasized on the optimization of the integrated heating resistor. Previous research has put the heater at either the cantilever clamp end, the midpoint or the free end. Aiming at sufficiently high and stable resonant amplitude, our research indicates that the optimized location of the thermal-electric exciting resistor is the clamp end instead of other positions. By both theoretical analysis and resonance experiments where three heating resistors are placed at the three locations of the fabricated cantilever, it is clarified that the clamp end heating provides the most efficient resonance excitation in terms of resonant amplitude, Q-factor and resonance stability. Besides, the optimized combination of dc bias and ac voltage is determined by both analysis and experimental verification. With the optimized heating excitation, the resonant cantilever is used for biotin–avidin-specific detection, resulting in a ±0.1 Hz ultra-low noise floor of the frequency signal and a 130 fg mass resolution. In addition to resonance excitation, the heater is used to heat up the cantilever for speed-up desorption after detection that helps rapid and repeated sensing to chemical vapor. The clamp end is determined (by simulation) as the optimal heating location for uniform temperature distribution on the cantilever. Using the resonant cantilever, a rapid and repeated sensing experiment on dimethyl methylphosphonate (DMMP) vapor shows that a short-period heating at the detection interval significantly quickens the signal recovery and enhances the sensing repeatability.

Handheld personal airborne nanoparticle detector based on microelectromechanical silicon resonant cantilever

“…where V DC , V AC , and x AC are the DC voltage, amplitude, and angular frequency (i.e., x AC = 2pf AC ) of the AC voltage, respectively [24][25][26][27].…”

Functionalized Mesoporous Silica for Microgravimetric Sensing of Trace Chemical Vapors

“…The design and fabrication details of the resonant microcantilevers used in this research have been given elsewhere. 17 In order to effectively suppress the interference signal from nonspecific adsorption of environmental moisture or organic molecules, the SiO 2 surface of the microcantilever is pretreated and passivated by self-assembling the molecules of FAS-17 (heptadecafluorodecyltrimethoxysilane, Gelest Inc.) that feature ultralow surface energy. Such a superhydrophobic and oleophobic reagent can effectively mask the silanol groups at the SiO 2 cantilever surface.…”

Hyper-branch sensing polymer batch self-assembled on resonant micro-cantilevers with a coupling-reaction route

“…The resonant micro-cantilevers are fabricated by using a standard silicon micromachining technology as we previously described in literatures [17][18][19].…”

“…Among various types of gas sensors, resonant micro-cantilevers are advantageous in ultra-high sensitivity, miniaturized size and facile integration with signalacquisition circuit [10][11][12][13][14][15][16][17][18][19]. For chemical sensing functionalization, sensing material with high specific surface area should be integrated onto the micro-gravimetric transducer of the resonant micro-cantilever.…”

“…Currently, the sensing materials in most researches are manually coated onto the desired micro-region of the cantilever in the way of one-by-one loading. Although some special coating techniques like ink-jet spotting and tiny-capillary incubation under optical microscope have been used, manual loading is really a difficult task to secure uniform sensing performance within a whole run of fabricated sensors [13,[19][20][21][22]. In our lab, a commercially available micro-manipulator equipped with a labmade capillary is employed to load the sensing material onto the desired micro-region of the cantilever [23][24][25][26][27][28][29].…”