MEMS Vaporizer

• US 20160007653A1
• Filed: 07/11/2014
• Published: 01/14/2016
• Est. Priority Date: 07/11/2014
• Status: Active Grant

• Current Assignee: Posita Technologies Incorporated
• Original Assignee: POSIFA Microsystems Inc.
• Inventors: Tu, Xiang Zheng
• Granted Patent: US 9,801,415 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A24F 40/10 Devices using liquid inhalable precursors
• CPC Class Codes: A24F 40/485 Valves; Apertures
• CPC Class Codes: A24F 40/70 Manufacture
• CPC Class Codes: F22B 1/282 with water or steam circulating in tubes or ducts
• CPC Class Codes: F22B 1/284 with water in reservoirs

Abstract

A MEMS vaporizer is described which can be used for electronic cigarettes. The vaporizer mainly composes: a silicon substrate, a micro-channel array, a membrane suspending over the micro-channel array and supported by the silicon substrate, a resistance heater and a resistance temperature sensor are disposed on the membrane. Since the vaporizer is a silicon-based integrated actuator which provides advantages including small size, compact structure, lower power consumption, lower cost, increased reliability, higher precision, and more environmental friendliness.

Claims

1. The MEMS vaporizer composes:

a silicon substrate, a micro-channel array created in the silicon substrate, a membrane suspending over the micro-channel array and supported by the silicon substrate, at least a resistance heater disposed on one side portion of the membrane and laterally across one end portion of the top of the micro-channel array, a resistance temperature sensor disposed on the membrane and adjacent to the resistance heater, two cavities are created in the silicon substrate and connected to the two end exits of the micro-channel array respectively, which all are integrated to be a vaporizer chip, a printed circuit board for packaging the vaporizer chip, a reservoir for inserting the printed circuit board with the vaporizer chip therein so as to dispose one cavity on its bottom and connect with one end exit of the micro-channel array, a liquid stored in the reservoir, and an air filter disposed on the top of the reservoir which allows air entering the reservoir and a same volume of the liquid in the reservoir entering the micro-channel array.

2. The MEMS vaporizer of claim 1, wherein said vaporizer is installed in an electronic cigarette for vaporizing an e-liquid usually containing a mixture of propylene glycol, vegetable glycerin, nicotine, and flavorings, while others releasing a flavored vapor without nicotine.

3. The MEMS vaporizer of claim 1, wherein said liquid contains the active ingredients of cannabis, which can be used for inhalation.

4. The MEMS vaporizer of claim 1, wherein said liquid contains an herb, oil, or wax, which can be used for inhalation.

5. The MEMS vaporizer of claim 1, wherein said liquid is driven to flow from the reservoir to the micro-channel array by capillary force that results from the interaction of cohesion of molecules of the liquid to each other and adhesion of these molecules to the constructing material of the micro-channel array.

6. The MEMS vaporizer of claim 1, wherein said resistance heater is used for allowing an electrical current to flow through therein and heat the liquid in the micro-channel array up to its boiling temperature so as to enable the phase change from the liquid to its vapor.

7. The MEMS vaporizer of claim 1, wherein said resistance temperature sensor is disposed with the resistance heater on the membrane, which allows for measuring the temperature of the resistance heater directly and accurately.

8. The MEMS vaporizer of claim 1, wherein said membrane has a sandwiched structure consisting of a bottom silicon nitride layer or the like, a central polysilicon layer, and a top silicon nitride layer or the like.

9. The MEMS vaporizer of claim 1, wherein said membrane has a sandwiched structure consisting of a bottom silicon nitride layer or the like, a central amorphous silicon layer, and a top silicon nitride layer or the like.

10. The MEMS vaporizer of claim 1, wherein said membrane has a sandwiched structure consisting of a bottom silicon nitride layer or the like, a central amorphous silicon carbide layer, and a top silicon nitride layer or the like.

11. The MEMS vaporizer of claim 1, wherein said resistance heater and resistance temperature sensor are passivated by coating a bottom silicon nitride layer or the like, and a top amorphous silicon carbide layer on their surface.

12. The MEMS vaporizer of claim 1, wherein said vaporizer is configured as:

the micro-channel array consisting of 1 to 30 micro-channels in which each micro-channel has a length ranging from 50 to 500 micron, a width ranging from 20 to 200 micron, and a height ranging from 10 to 50 micron, and two adjacent micro-channels are separated by a trapezium-shape side wall with a top width ranging from 2 to 20 micron.

13. The MEMS vaporizer of claims 1 and 8, wherein said central polysilicon layer has a thickness ranging from 2 to 5 micron, both said bottom and top layer have a thickness ranging from 1000 to 8000 angstrom.

14. The MEMS vaporizer of claims 1 and 9, wherein said central amorphous silicon layer has a thickness ranging from 2 to 5 micron, said bottom and top layer have a thickness ranging from 1000 to 8000 angstrom.

15. The MEMS vaporizer of claims 1 and 10, wherein said central amorphous silicon carbide layer has a thickness ranging from 2 to 5 micron, said bottom and top layer have a thickness ranging from 1000 to 8000 angstrom.

16. The MEMS vaporizer of claim 1, wherein said the resistance heater is made of Ta—

Al or Ni—

Cr alloy thin film, or the like which has a resistance ranging from 1 to 100 ohm.

17. The MEMS vaporizer of claim 1, wherein said the resistance temperature sensor is made of Ni metal thin film or the like which has a resistance ranging from 100 to 1000 ohm.

18. The MEMS vaporizer of claim 1, wherein said air filter is made of PTFE, regenerated cellulose, nylon, cellulose nitrate, polycarbonate, aluminum oxide, etc.

19. A method of manufacturing said MEMS vaporizer in claim 1 of the MEMS vaporizer, which comprises steps of:

Providing a silicon substrate having a resistivity ranging from 0.1 to 0.001 ohm-cm and a (100) crystal orientation;

Depositing a silicon nitride layer on the surface of the silicon substrate by LPCVD (low pressure chemical vapor deposition) which has a thickness ranging from 2000 to 3000 angstrom;

Performing a lithographic process for creating a silicon revealed rectangular array in the silicon nitride layer;

Performing an anodization process in a HF solution for converting the revealed silicon rectangular array into a porous silicon array;

Depositing a bottom silicon nitride layer or the like by LPCVD or PECVD (plasma enhance chemical vapor deposition) on the surface of the porous silicon array, which has a thickness ranging from 1000 to 8000 angstrom;

Depositing a central polysilicon layer by LPCVD, or a central amorphous silicon layer by PECVD, or a central amorphous silicon carbide layer by PECVD on the surface of the bottom silicon nitride layer or the like which has a thickness ranging from 2 to 5 micron;

Depositing a top silicon dioxide layer or the like on the surface of the central polysilicon layer, or central amorphous silicon layer, or central amorphous silicon carbide layer, which has a thickness ranging from 1000 to 8000 angstrom;

Creating at least a resistance heater on the top of the porous silicon array by sputtering and photolithography;

Creating a resistance temperature sensor, an electrical interconnection, and several bonding pads on the top of the silicon substrate including the porous silicon array by photolithography process, sputtering, and plating;

Depositing a passivation layer on the top of the resistance heater and resistance temperature sensor by PECVD, which consists of a bottom silicon nitride layer or the like with a thickness ranging from 2000 to 5000 angstrom and a top silicon carbide layer with a thickness ranging from 2000 to 5000 angstrom;

Performing a photolithography process and a dry etching process for creating two cavities recessed in the silicon substrate, and connecting to the two side end portions of the porous silicon array respectively, which have a length equal to the width of the porous silicon array and a width ranging from 200 to 400 micron;

Etching porous silicon in a dilute KOH solution for creating a micro-channel array and a membrane, which all result in a completed vaporizer chip.

20. The method of claim 19, wherein further comprises a step of installing the vaporizer chip on a printed circuit board (PCB) by mounting and wire bonding so as to connect the micro-channel array with a control circuit.

21. The method of claim 19, wherein further comprises a step of inserting the printed circuit board with the vaporizer chip into a molted plastic reservoir so that the micro-channel array of the vaporizer can be provided with a liquid stored in the reservoir.

22. The method of claim 19, wherein said HF solution for the anodization process consists of one or two parts 48 wt % HF and 1 part ethanol and an anodic current density ranging from 40 to 80 mA/cm.sup.2.

23. The method of claim 19, wherein said porous silicon array consists of 1 to 30 porous silicon rectangular regions in which each rectangular region has a length ranging from 50 to 500 micron, a width ranging from 20 to 200 micron, and a depth ranging from 10 to 50 micron, and two adjacent regions are separated by a trapezium side wall with a top width ranging from 2 to 20 micron.

24. The method of claim 19, wherein said resistance heater is made of Ta—

Al or Ni—

Cr alloy thin film, or the like and has a resistance ranging from 1 to 100 ohm.

25. The method of claim 19, wherein said resistance temperature sensor is made of Ni metal thin film or the like and has a resistance ranging from 100 to 1000 ohm.

The method of claim 19, wherein said wet etching porous silicon is performed in a diluted KOH solution which contains 1-2 volume % KOH in DI water.