Silicon three-dimensional phononic crystal based on cantilever beam structure

Abstract

The invention discloses a silicon three-dimensional phononic crystal based on a cantilever beam structure, which is composed of phononic crystal primitive cells in a periodic array, the primitive cells are formed by connecting a single material silicon with a mass unit as a center and a single-point or multi-point cantilever beam structure, and a cantilever beam spirally surrounds the mass unit with the same gap. The silicon three-dimensional phononic crystal provided by the invention can be used as a phononic crystal primitive cell periodic array to form an outer frame to be arranged around devices such as an MEMS (Micro Electro Mechanical System) micromechanical gyroscope, an accelerometer and the like, and the external vibration frequency is absorbed through a local resonance principle to perform vibration isolation. The defects that a traditional three-dimensional photonic crystal needs various materials, is complex in structure, large in size and the like are overcome, the low-frequency band gap of 10 kHz and below can be achieved, the structure is simple and changeable, the band gap range is easy to adjust and control, and therefore the wide application prospect is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of micro-electromechanical systems (MEMS) phononic crystals, and in particular relates to a silicon three-dimensional phononic crystal based on a cantilever beam structure. Background Art

[0002] Phononic crystals are artificial composite materials formed by the periodic arrangement of different materials. The essence of structural vibration is the propagation of elastic waves. When elastic waves propagate in phononic crystals, they are affected by their internal periodic structure and can suppress the propagation of elastic waves within a specific frequency range. This frequency range is called the "bandgap frequency". In theory, the propagation of elastic waves within the bandgap frequency range will be suppressed, and only elastic waves in other frequency ranges can continue to propagate through phononic crystals. Therefore, this characteristic can be applied to the field of vibration isolation. By designing the material properties and geometric structure parameters of phononic crystal primitive cells, adjusting the bandgap frequency range in the energy band structure, and then arranging the periodic array of phononic crystal primitive cells as an external frame around MEMS micromechanical gyroscopes, accelerometers and other devices, it is possible to effectively achieve the purpose of controlling noise and vibration and improve their test performance and reliability.

[0003] One-dimensional and two-dimensional phononic crystals are based on the Bragg reflection mechanism, while three-dimensional phononic crystals are based on the principle of local resonance. For phononic crystals based on Bragg scattering, the lattice size is at the same order of magnitude as the half-wavelength of the elastic wave, and the vibration frequency of the phononic crystal is f=Nv / 2a, where N is a positive integer, v is the elastic wave velocity, and a is the lattice size of the phononic crystal. According to the above relationship, to achieve a band gap in the kHz range, the lattice size of the phononic crystal must be on the order of several meters, which is far beyond the scope of feasibility. The band gap frequency of the local resonance type phononic crystal is two orders of magnitude smaller than that of the Bragg type phononic crystal of the same size, and a low-frequency band gap can be achieved. The principle is that the local resonance type phononic crystal has a strong response to vibrations within a specific frequency range. Elastic waves of a specific frequency will excite the local unit of the phononic crystal to resonate, and the propagated energy will be absorbed by the phononic crystal, thereby achieving a vibration isolation effect.

[0004] As a new type of vibration isolation material, local resonance phononic crystals have the characteristics of elastic wave band gap in the low frequency band and have great potential in the field of micro-electromechanical system (MEMS) vibration isolation. Traditional local resonance phononic crystals are mainly composed of soft rubber and epoxy resin, and the properties of the two materials are very different. It uses the difference in the intrinsic properties between these materials to achieve local resonance, thereby obtaining a low-frequency band gap. In addition, traditional local resonance phononic crystals generally have a complex structure, so the preparation process is cumbersome and not conducive to assembly and application. Summary of the invention

[0005] The purpose of the present invention is to provide a silicon three-dimensional phononic crystal based on a cantilever beam structure, which adopts a single material silicon, a mass unit of the same thickness and a cantilever beam structure, thereby overcoming the cumbersome materials and processes for preparing three-dimensional local resonance type phononic crystals; the silicon three-dimensional phononic crystal provided by the present invention is used as a periodic array of phononic crystal primitives to form an outer frame arranged around MEMS micromechanical gyroscopes, accelerometers and other devices, absorbs the vibration frequency transmitted from the outside, suppresses the influence of external vibration on the accuracy of micromechanical (MEMS) devices, and improves their anti-vibration performance; the silicon three-dimensional phononic crystal provided by the present invention has a simple and changeable structure, the frequency band gap range is easy to adjust, and the applicability is strong.

[0006] The implementation scheme of the present invention is:

[0007] A silicon three-dimensional phononic crystal based on a cantilever beam structure is composed of a periodic array of phononic crystal primitive cells. The primitive cells are made of a single material, silicon, and are centered on a mass unit. The cantilever beam structure is connected at a single point or multiple points. The cantilever beam spirally surrounds the mass unit with the same gap.

[0008] Compared with the prior art, the present invention has the following significant advantages:

[0009] The present invention provides a silicon three-dimensional phononic crystal based on a cantilever beam structure, which adopts a single material silicon, a single thickness, a variable and simple structure, strong designability, and is suitable for MEMS processing technology and various MEMS devices; the present invention adopts a method of connecting the cantilever beam at a single point or multiple points with a mass unit as the center to realize a three-dimensional phononic crystal structure, has a lower natural frequency, and thus can realize a low-frequency band gap; the present invention has the advantage of adjusting the frequency band gap range by modifying relevant dimensional parameters, and is suitable for isolating vibrations of different frequencies. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Schematic diagram of the two-dimensional structure of the silicon three-dimensional phononic crystal unit cell according to Example 1 of the present invention;

[0011] Figure 2 Schematic diagram of the three-dimensional structure of the silicon three-dimensional phononic crystal unit cell according to Example 1 of the present invention;

[0012] Figure 3 Schematic diagram of the two-dimensional structure of a silicon three-dimensional phononic crystal unit cell according to Example 2 of the present invention;

[0013] Figure 4 Schematic diagram of the three-dimensional structure of a silicon three-dimensional phononic crystal unit cell according to Example 2 of the present invention;

[0014] Figure 5 Schematic diagram of the two-dimensional structure of the silicon three-dimensional phononic crystal unit cell according to Example 3 of the present invention;

[0015] Figure 6Schematic diagram of the three-dimensional structure of a silicon three-dimensional phononic crystal unit cell according to Example 3 of the present invention;

[0016] Figure 7 Schematic diagram of the two-dimensional structure of a silicon three-dimensional phononic crystal unit cell according to Example 4 of the present invention;

[0017] Figure 8 Schematic diagram of the three-dimensional structure of the silicon three-dimensional phononic crystal unit cell according to Example 4 of the present invention;

[0018] Fig. 9 The energy band structure diagram of the silicon three-dimensional phononic crystal unit cell of Example 1 of the present invention at 4.66-8.01 kHz;

[0019] Fig.10 The energy band structure diagram of the silicon three-dimensional phononic crystal unit cell of Example 2 of the present invention at 9.58-14.31 kHz;

[0020] Fig.11 The energy band structure diagram of the silicon three-dimensional phononic crystal unit cell of Example 3 of the present invention at 8.39-11.46 kHz;

[0021] Fig.12 The energy band structure diagram of the silicon three-dimensional phononic crystal unit cell of Example 4 of the present invention at 7.92-11.20 kHz;

[0022] Fig.13 This is a planar structural dimension diagram of a silicon three-dimensional phononic crystal unit cell according to Example 3 of the present invention;

[0023] Fig.14 The energy band structure diagram of the silicon three-dimensional phononic crystal unit cell of Example 3 of the present invention at 9.91-15.12 kHz;

[0024] Fig.15 This is a diagram of the energy band structure of the silicon three-dimensional phononic crystal unit cell of Example 3 of the present invention at 5.85 to 8.77 kHz. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0026] Example 1

[0027] A silicon three-dimensional phononic crystal based on a cantilever beam structure in this embodiment, such as Figure 1 As shown, it includes a centrally arranged mass unit (101) and a surrounding cantilever beam (201), one end of which is connected to a vertex of the mass unit and spirally surrounds the mass unit with the same gap. The schematic diagram of its three-dimensional structure is shown in Figure 2 shown.

[0028] Example 2

[0029] A silicon three-dimensional phononic crystal based on a cantilever beam structure in this embodiment, such as Figure 3 As shown, it includes a centrally arranged mass unit (102) and four surrounding cantilever beam structures (202, 203, 204, 205), one end of each of the four surrounding cantilever beams (202, 203, 204, 205) is connected to the four vertices of the mass unit, and spirally surrounds the mass unit with the same gap in sequence. The schematic diagram of its three-dimensional structure is shown in Figure 4 shown.

[0030] Example 3

[0031] On the basis of Example 2, the cantilever beam of this embodiment further includes four folding cantilever beams, such as Figure 5 As shown, the four folding cantilever beams (301, 302, 303, 304) are respectively arranged in four directions of the mass unit (103); one end of the four folding cantilever beams (301, 302, 303, 304) is respectively connected to the four vertices of the mass unit; the other end of the four folding cantilever beams (301, 302, 303, 304) is connected to the four surrounding cantilever beams (206, 207, 208, 209). The four folding cantilever beams (301, 302, 303, 304) and the four surrounding cantilever beams (206, 207, 208, 209) spirally surround the mass unit with the same gap. Its three-dimensional structure schematic diagram is as follows Figure 6 shown.

[0032] Example 4

[0033] A silicon three-dimensional phononic crystal based on a cantilever beam structure in this embodiment, such as Figure 7 As shown, it includes a centrally arranged mass unit (104), two surrounding cantilever beams (210, 211) and four folding cantilever beams (305, 306, 307, 308), one end of the two surrounding cantilever beams (210, 211) are respectively connected to the diagonal of the mass unit (104), and spirally surround the mass unit (104) layer by layer with the same gap; one end of the four folding cantilever beams (305, 306, 307, 308) is connected to the outermost layer of the two surrounding cantilever beams (210, 211); the four folding cantilever beams (305, 306, 307, 308) are respectively arranged in four directions of up, down, left and right.

[0034] The three-dimensional phononic crystal preparation material described in the present invention is silicon, and its material parameters include but are not limited to density ρ=2330kg / m3, Young's modulus E=1.69e11Pa, Poisson's ratio ν=0.28;

[0035] Fig. 9 is a diagram of the energy band structure in Example 1 of the present invention; Fig.10 is an energy band structure diagram in Example 2 of the present invention; Fig.11 is a diagram of the energy band structure in Example 3 of the present invention; Fig.12 4 is a diagram of the energy band structure in Example 4 of the present invention. It can be seen that the band gap frequency range of the silicon three-dimensional phononic crystal unit cell that suppresses elastic wave propagation.

[0036] Further, the method for adjusting the band gap frequency range of the silicon three-dimensional phononic crystal in the embodiment is: taking the silicon three-dimensional phononic crystal structure in Example 3 as an example, the band gap frequency range is adjusted by modifying the geometric parameters; the planar structure size diagram is as shown in Fig.13 As shown: the length and width are both the side length a, the beam width b, the length and width of the middle mass block are both the side length c, the gap between the beams d, and the thickness h.

[0037] The method of modifying the geometric parameters includes but is not limited to: 1. Modifying the gap d between the cantilever beams to adjust the band gap frequency. By reducing the gap d of the silicon three-dimensional phononic crystal in Example 3, the band gap frequency range can be adjusted from 8.39 to 11.46 kHz to 9.91 to 15.12 kHz. Fig.14 Second, the band gap frequency can be adjusted by adjusting the number of surrounding layers of the cantilever beam structure: this is equivalent to only increasing the side length a, and the frequency range can be adjusted from 8.39 to 11.46 kHz to 5.85 to 8.77 kHz, as shown in Figure 2. Fig.15 shown.

[0038] In summary, the phononic crystals in the embodiments have the characteristic of easily adjustable band gap frequency range, and can be arranged in an array of phononic crystal cells around MEMS gyroscopes, accelerometers, or other micro-components susceptible to vibration interference, thereby suppressing parasitic interference caused by external vibrations within their operating frequency range, thereby isolating the influence of external vibrations and improving their anti-vibration performance and detection accuracy.

[0039] In an embodiment of the present invention, the three-dimensional phononic crystal structure of the present invention is realized by connecting the cantilever beam at a single point or multiple points with the mass unit as the center, and has a lower natural frequency. Therefore, a low-frequency band gap of 10kHz and below can be realized through the principle of local resonance, and the band gap range is easy to control, which can be applicable to the silicon operating frequency;

[0040] The three-dimensional phononic crystal structure adopts a single-layer structure as a whole, the mass unit and the cantilever beam structure are made of the same material and have the same thickness, and are manufactured in one step using the MEMS process, thus overcoming the shortcomings of the local resonance type three-dimensional phononic crystal structure being complex and cumbersome to manufacture.

Claims

1. A silicon three-dimensional phononic crystal based on a cantilever beam structure, consisting of a periodic array of phononic crystal primitive cells, It is characterized in that The primitive cell is made of a single material, silicon, with a mass unit as the center, and is constructed in a single-point or multi-point connected cantilever beam structure, and the cantilever beam spirally surrounds the mass unit with the same gap.

2. The silicon three-dimensional phononic crystal based on the cantilever beam structure according to claim 1, It is characterized in that The cantilever beam comprises four surrounding cantilever beams, one end of each of which is connected to four vertex corners of the mass unit respectively and spirally surrounds the mass unit.

3. The silicon three-dimensional phononic crystal based on the cantilever beam structure according to claim 2, It is characterized in that The cantilever beam also includes four folded cantilever beams, which are respectively arranged in four directions of the mass unit; one end of the four surrounding cantilever beams is respectively connected to the four top corners of the mass unit through a folded cantilever beam, spirally surrounding the mass unit.

4. The silicon three-dimensional phononic crystal based on the cantilever beam structure according to claim 1, It is characterized in that The cantilever beam includes two wraparound cantilever beams and four folding cantilever beams, one end of the two wraparound cantilever beams are respectively connected to the diagonals of the mass unit, spirally wrapping around the mass unit layer by layer; one end of the four folding cantilever beams is connected to the outermost layer of the two wraparound cantilever beams; the four folding cantilever beams are respectively arranged in four directions of up, down, left and right.

5. The silicon three-dimensional phononic crystal based on the cantilever beam structure according to claim 1, It is characterized in that The bandgap frequency can be tuned by adjusting the gap of the cantilever beam, the number of surrounding layers, and the size of the mass unit.

6. The silicon three-dimensional phononic crystal based on the cantilever beam structure according to claim 1, It is characterized in that It is arranged around the device using MEMS technology.

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