Pump and actuator

Abstract

A first surface of a porous medium is in contact with a first space. A second surface of the porous medium is in contact with a second space. The first space is in communication with the second space via the pores of the porous medium. Light in a wavelength range where the material of the porous medium exhibits light absorption properties is applied to the first surface of the porous medium from a light source, so that energy of the applied light can be efficiently absorbed into the porous medium from its first surface, and the first surface of the porous medium can be efficiently heated. As a result, a thermal transpiration flow can be efficiently generated in the porous medium, and a pressure difference can be efficiently produced between the first space and the second space.

What is claimed is: 
     
         1 . A pump comprising:
 a porous medium which has light absorption properties in a predetermined wavelength range and which has pores; and   a heating unit which applies electromagnetic waves having a peak of radiant intensity in the predetermined wavelength range to a first surface of the porous medium to heat the first surface of the porous medium,   wherein the first surface of the porous medium is in contact with a first space,   a second surface of the porous medium different from the first surface is in contact with a second space,   the first space is in communication with the second space via the pores, and   a gas in the second space can be transferred to the first space via the communication pores.   
     
     
         2 . The pump according to  claim 1 , wherein the pores of the porous medium have a diameter equal to or less than a length that is five times the mean free path of the gas filling the first space or the second space. 
     
     
         3 . The pump according to  claim 1 , wherein the electromagnetic waves are applied to the first surface of the porous medium via a transmission window having light transmission properties in the predetermined wavelength range. 
     
     
         4 . The pump according to  claim 1 , further comprising a heat radiation device for heat radiation in the second surface of the porous medium. 
     
     
         5 . The pump according to  claim 1 , wherein the porous medium has a peak of light absorption properties for infrared light, and
 the heating unit applies electromagnetic waves having a peak of radiant intensity in an infrared light region to the first surface of the porous medium.   
     
     
         6 . The pump according to  claim 1 , wherein the porous medium has a peak of light absorption properties for visible light, and
 the heating unit applies electromagnetic waves having a peak of radiant intensity in a visible light region to the first surface of the porous medium.   
     
     
         7 . The pump according to  claim 1 , wherein the porous medium is made of silicon dioxide, and
 the predetermined wavelength range is 2.3 μm or more.   
     
     
         8 . The pump according to  claim 1 , wherein the porous medium is made of silicon dioxide, and
 the predetermined wavelength range is 2.3 to 4.0 μm.   
     
     
         9 . The pump according to  claim 1 , wherein the porous medium is made of silicon dioxide, and
 the predetermined wavelength range is 2.5 to 3.8 μm or is 4.8 μm or more.   
     
     
         10 . The pump according to  claim 1 , wherein gas molecules in the second space are transferred to the first space by a thermal transpiration flow generated in the pores. 
     
     
         11 . An actuator comprising a drive unit based on a pressure difference produced between the first space and the second space by the pump according to  claim 1 . 
     
     
         12 . The pump according to  claim 1 , wherein the first space is in communication with a third space having a liquid discharge opening,
 the pump being configured to pressurize the third space to discharge a liquid in the third space from the liquid discharge opening.   
     
     
         13 . The pump according to  claim 1 , wherein the second space is in communication with a fourth space having a liquid suction opening,
 the pump being configured to depressurize the fourth space to suck a liquid into the fourth space from the liquid suction opening.   
     
     
         14 . The pump according to  claim 1 , further comprising:
 a first valve which permits or cuts off the communication between a fifth space having a liquid transfer opening and the first space; and   a second valve which permits or cuts off the communication between the fifth space and the second space,   the pump having a discharge unit to discharge a liquid in the fifth space from the liquid transfer opening by using the first valve to permit the communication between the fifth space and the first space and using the second valve to cut off the communication between the fifth space and the second space, and   a suction unit to suck a liquid into the fifth space from the liquid transfer opening by using the first valve to cut off the communication between the fifth space and the first space and using the second valve to permit the communication between the fifth space and the second space.   
     
     
         15 . A pump comprising:
 a porous medium having pores; and   a device which brings the temperature of a first surface of the porous medium to a temperature higher than the temperature of a second surface of the porous medium different from the first surface,   wherein the first surface of the porous medium is in contact with a first space,   the second surface of the porous medium different from the first surface is in contact with a second space,   the first space is in communication with the second space via the pores,   a gas in the second space can be transferred to the first space via the communication pores,   the first space is in communication with a third space having a liquid discharge opening, and   a liquid in the third space can be discharged from the liquid discharge opening by the pressurization of the third space.   
     
     
         16 . A pump comprising:
 a porous medium having pores, and   a device which brings the temperature of a first surface of the porous medium to a temperature higher than the temperature of a second surface of the porous medium different from the first surface,   wherein the first surface of the porous medium is in contact with a first space,   the second surface of the porous medium different from the first surface is in contact with a second space,   the first space is in communication with the second space via the pores,   a gas in the second space can be transferred to the first space via the communication pores,   the second space is in communication with a fourth space having a liquid suction opening, and   a liquid can be sucked into the fourth space from the liquid suction opening by the depressurization of the fourth space.   
     
     
         17 . An electricity generating equipment configured to generate electricity by using the pump according to  claim 1 . 
     
     
         18 . An electricity generating equipment configured to generate electricity by using the pump according to  claim 15 . 
     
     
         19 . An electricity generating equipment configured to generate electricity by using the pump according to  claim 16 . 
     
     
         20 . The pump according to  claim 1 , wherein the first surface is one main surface of the porous medium, and
 the second surface is a surface of the porous medium opposite to the one main surface.   
     
     
         21 . The pump according to  claim 15 , wherein the first surface is one main surface of the porous medium, and
 the second surface is a surface of the porous medium opposite to the one main surface.   
     
     
         22 . The pump according to  claim 16 , wherein the first surface is one main surface of the porous medium, and
 the second surface is a surface of the porous medium opposite to the one main surface.