Mass-Fabrication Scheme of Highly Sensitive Wireless Electrodeless MEMS QCM Biosensor with Antennas on Inner Walls of Microchannel

Abstract

Quartz-crystal-microbalance (QCM) biosensor is a typical label-free biosensor, and its sensitivity can be greatly improved by removing electrodes and wires that would be otherwise attached to the surfaces of the quartz resonator. The wireless-electrodeless QCM biosensor was then developed using a microelectro-mechanical systems (MEMS) process, although challenges remain in the sensitivity, the coupling efficiency, and the miniaturization (or mass production). In this study, we establish a MEMS process to obtain a large number of identical ultrasensitive and highly efficient sensor chips with dimensions of 6 mm square. The fundamental shear resonance frequency of the thinned AT-cut quartz resonator packaged in the microchannel exceeds 160 MHz, which is excited by antennas deposited on inner walls of the microchannel, significantly improving the electro-mechanical coupling efficiency in the wireless operation. The high sensitivity of the developed MEMS QCM biosensors is confirmed by the immunoglobulin G (IgG) detection using protein A and ZZ-tag displaying a bionanocapsule (ZZ-BNC), where we find that the ZZ-BNC can provide more effective binding sites and higher affinity to the target molecules, indicating a further enhancement in the sensitivity of the MEMS QCM biosensor. We then perform the label-free C-reactive protein (CRP) detection using the ZZ-BNC-functionalized MEMS QCM biosensor, which achieves a detection limit of 1 ng mL–1 or less even with direct detection.

GHz surface-wave phononic crystal biosensor using a Fano resonance at the bandgap edge

“…[36][37][38] For example, the widely studied quartz-crystal microbalance (QCM) biosensor can be used for the real-time, label-free detection of biomolecules by measuring changes in resonant frequency. [39][40][41] The PnC in this study can also be used as a biosensor by attaching biomolecules on the pillar surfaces, but with a much higher working freqeuncy than that of QCM. We propose a SAW biosensor design based on the Fano resonance of the pillar-type PnC studied here, operating with picosecond ultrasonics (see the supplementary material for details).…”

Ultrasensitive wireless quartz crystal microbalance bio/gas sensors

“…36) The instrument for QCM experiments can be a commercially available network analyzer. 30,31,40) Decay-curve measurement has also been used for measuring the decay curve after the excitation of the resonator, 41) which allows evaluation of the dissipation of the resonator vibration. 42) In the case of wireless experiments, a higher power pulse excitation is needed, and this is analogically achieved by combining a high-power gated amplifier and a superheterodyne spectrometer.…”

“…Recently, a breakthrough technology has been developed that dramatically improves the excitation efficiency. 35) Its structure is shown in Fig. 22.…”

“…Then, by introducing MEMS processes, the resonator can be made even thinner and the sensor chips can be mass-produced. [28][29][30][31][32][33][34][35] The thinner resonator increases the measurement frequency, achieving battery-free wireless experiments at distances of 10 m or more. 36) This paper outlines the mechanisms of WE-QCM sensors and their recent applications.…”

“…This MEMS process consists of four processes: (i) a glass-wafer process for fabricating the upper and bottom glass wafers with microchannels and inner and outer antennas; (ii) a silicon-on-insulator wafer process for making the middle Si layer as the bonding layer; (iii) a quartz-wafer process for patterning the isolated thin quartz resonators; and (iv) the packaging process. (Reprinted with permission from Ref 35…”