Micromachined high-Q fused silica bell resonator with complex profile curvature realized using 3D micro blowtorch molding

Abstract

We present a high level of control over complex profile curvature in micro fused silica shell resonators achieved through a blowtorch molding process. The graphite mold geometry is imparted on the shell without transferring the texture, preserving the 2.4 Å surface roughness of the reflowed fused silica. A variety of shapes are possible using this technique, including a bell shape with a height-to-radius ratio of 1.2. The shell will gently curve around sharp corners but can also follow a curvature prescribed by a rounded or conical sidewall. We offer an explanation for the mechanism that enables this process. We also discuss simulation results on anchor loss and thermoelastic damping and measure ring-down times of 6.7 seconds at ~12.9 kHz for both n = 2 wineglass modes of a bell resonator.

Recent Advances in MEMS-Based 3D Hemispherical Resonator Gyroscope (HRG)—A Sensor of Choice

“…In contrast to micro-scale high-temperature glassblowing inside a furnace, another process based on thermos-forming of fused silica involves using a blow-torch technique. Cho et al [ 50 , 69 , 82 , 98 , 99 , 100 ], Shiari et al [ 101 ], Nagourney et al [ 102 , 103 ], Woo et al [ 104 ], and Singh et al [ 52 ] fabricated a microscale shell gyroscope using a blow-torching process assembled on an electrode substrate called the birdbath resonator gyroscope (BRG) ( Figure 13 ). This is another type of wineglass design where the stem is located outside of the hemisphere.…”

“…The size and position of the anchor (stem) of the HRG has a great influence on the Q-factor [ 108 ]. Cho and Najafi [ 109 ] used the same method of fabrication process discussed in [ 82 , 85 , 98 , 99 , 100 , 101 , 102 ] to build an HRG with a solid stem, which had the advantages of low anchor loss due to the large stem length/stiffness ratio and small shell rim thickness. At <10 μTorr vacuum, the n = 2 wineglass mode had a frequency of 22.6 kHz and Q = 2.55 million [ 109 ].…”

“…Li et al [ 110 ] used a combination of a blow-torching process and a highly precise mold to fabricate FS HRGs with the same method as [ 69 , 82 , 98 , 99 , 100 , 101 , 102 , 103 , 104 ]. Using a high-precision machining process, upper and lower graphite molds were fabricated.…”

Theoretical prediction of soft-forming micro-hemispherical shells from fused silica substrates in reclining mold

“…In recent years, to obtain highly symmetric micro-hemispherical resonators, methods for the preparation of high-quality micro-hemispherical resonators have attracted considerable attention. Various preparation methods have been introduced for obtaining micro-hemispherical resonators, including isotropic etching and deposition [5][6][7][8], chemical foaming [9][10][11][12], and high-temperature glass blowing [13][14][15][16][17][18]. Among them, one isotropic etching method is used to etch polycrystalline diamond, polycrystalline silicon, and alumina to fabricate micro-hemispherical shells [6][7][8].…”