Patent Publication Number: US-2021189310-A1

Title: Semiconductor cell culture device and a system for three-dimensional cell culture

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is based on priority claimed on European Patent Application No. 19218559.3, filed on Dec. 20, 2019, the contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present inventive concept relates to a semiconductor cell culture device, which may or may not be used for analysis and/or actuation of a three-dimensional cell culture. 
     BACKGROUND 
     Culturing of three-dimensional cell constructs is of high interest, since it may enable studying of three-dimensional structures that mimic structures found in living organisms, such as mimicking brain structures. This may be useful e.g. for neuroscience research. 
     However, three-dimensional cell and tissue constructs may not allow for making measurements, such as recording electrical signals or potentials, in interior parts within the three-dimensional structure. Further, some constructs may also require nutrient delivery throughout the construct, and this may be difficult to provide. 
     SUMMARY 
     It is an object of the present inventive concept to provide a cell culture device which may facilitate culturing of three-dimensional cell cultures. It is a particular object of the present inventive concept to provide a cell culture device which may allow for making measurements interior to a three-dimensional cell culture. 
     These and other objects of the invention are at least partly met by the invention as defined in the independent claims. Preferred embodiments are set out in the dependent claims. 
     According to a first aspect, there is provided a semiconductor cell culture device for three-dimensional cell culture, said device comprising: a semiconductor material layer in which a cell culture portion of semiconductor material is defined, wherein the cell culture portion defines an area within the semiconductor material layer surrounded by semiconductor material, wherein the cell culture portion comprises a mesh structure having island structures being interconnected by bridge structures and defining through-pores between the island structures allowing for selective transport of cell constructs, cellular components, proteins or other large molecules through the semiconductor material layer and on opposite sides of the cell culture portion in the semiconductor material layer, and a supporting structure connected to the cell culture portion. 
     Thanks to the through-pores being provided in the mesh structure, a through flow is provided through the mesh structure. This through flow may allow cell constructs to be formed to extend through the mesh structure and, thus, be arranged on opposite sides of the cell culture portion. Hence, the island structures and bridge structures may be formed within a cell culture and extend into the interior of a three-dimensional cell culture. This may be used for analysis of interior portions of the three-dimensional cell culture. However, the semiconductor cell culture device need not necessarily be used for analysis of the three-dimensional cell culture. Even though a semiconductor structure is suitable for providing electronic circuitry thereon, the semiconductor cell culture device can be used merely to define a structure for cell culture. The semiconductor structure may be used for defining a geometry that may stimulate a particular cell culture for controlling the cell culture. For instance, the size of through-pores may control the cell culture. The semiconductor cell structure device may also in some embodiments be configured such that the mesh structure assumes a desired shape in three dimensions, which may stimulate forming of a desired three-dimensional shape of a cell construct. In this case, it is possible to utilize strains within the mesh structure that may be created in the island structures and bridge structures, such that the strains may force a planar semiconductor material layer in which the mesh structure is created to transform into a desired shape. 
     Thanks to the use of a semiconductor material, such as silicon, the forming of the mesh structure may be easily controlled for defining a small structure with desired geometry. Using conventional semiconductor manufacturing technology, it is possible to define minute structures in a very accurate manner. Thus, the cell culture portion being formed in a semiconductor material layer enables accurate manufacture of desired shapes and sizes of structures within the cell culture portion. The size and shape of parts of the mesh structure may thus be accurately controlled by the mesh structure being formed in a semiconductor material layer. 
     The through flow may allow for selective transport of cell constructs, cellular components, proteins or other large molecules through the semiconductor material layer. Thus, a size of the through-pores may control the selective transport. The through-pores may be sufficiently large to allow cell bodies to pass therethrough. However, in some embodiments, the through-pores may have a size of approximately 5 μm or approximately 2.5 μm or therebetween, which may allow neurites to pass through the through-pores but prevent cell bodies to pass therethrough. In such case, the through-pores may be used for allowing transport of components through the mesh structure so as to facilitate nutrient delivery through the mesh structure even though cell constructs may not necessarily be grown through the mesh structure. 
     The cell culture portion may be defined in a semiconductor material layer. This implies that the cell culture portion may, during manufacture, be formed in a planar layer. For instance, the cell culture portion may be formed in a semiconductor substrate, such as a silicon wafer. The cell culture portion may thus extend in a plane. However, the cell culture portion need not necessarily extend in a plane in the semiconductor cell culture device. Rather, the semiconductor material layer may assume a three-dimensional shape such that the cell culture portion extends in three dimensions, e.g. a helical shape, which may be useful in controlling a desired shape of a cell construct. 
     The cell culture portion defines an area in the semiconductor material layer. Thus, the cell culture portion is surrounded by semiconductor material. Hence, the cell culture portion may define through-pores as the only connections between opposite sides of the cell culture portion. This is advantageous in controlling culture of cell constructs on opposite sides and/or through the cell culture portion. 
     The supporting structure may be configured to provide support on opposite sides of the area of the cell culture portion, i.e. at opposite sides of a periphery of the cell culture portion in the semiconductor material layer. This may be useful when the cell culture portion is extending in a plane, whereby the supporting structure may provide stability to ensure that the cell culture portion is maintained in the plane. Also, the supporting structure may be thicker than the cell culture portion, which may be used for creating a space between the cell culture portion and another structure, for example another cell culture portion on another semiconductor cell culture device when such devices are stacked. 
     However, it should be realized that the supporting structure may alternatively be provided on only one side of the area of the cell culture portion. For instance, a portion of the semiconductor material layer with the cell culture portion may extend as a cantilever structure from the supporting structure. 
     The supporting structure may be formed in the semiconductor material layer for being connected to the cell culture portion. For instance, the supporting structure may be a portion of the semiconductor material layer that may or may not have a larger thickness than the cell culture portion in the semiconductor material layer. Alternatively or additionally, the supporting structure may comprise a structure that is attached to a portion of the semiconductor material layer for connecting the supporting structure to the cell culture portion. 
     The semiconductor cell culture device may be used for probing into a three-dimensional cell culture. For instance, the supporting structure may be arranged external to the cell culture with the cell culture portion extending from the supporting structure in a cantilever-type arrangement. The cell culture may then extend on opposite sides of the cell culture portion and may further extend around an end of the semiconductor material layer in which the cell culture portion is defined. 
     The semiconductor cell culture device may alternatively be arranged with supporting structures on opposite sides of a three-dimensional cell culture. This may be particularly useful if the semiconductor cell culture device is to be stacked so as to provide two or more cell culture portions extending e.g. in parallel planes through a cell culture. 
     As used herein, a “cell construct” should be understood as any cell or combination of cells that may form a three-dimensional shape. 
     It should be realized that the cell culture portion being defined in the semiconductor material layer may also extend in one or more additional layers above or below the semiconductor material layer. Thus, for instance if an electronic circuitry is defined in the mesh structure, additional dielectric layer(s) may be provided on the semiconductor material layer for providing e.g. metal structures on the dielectric layer(s). Thus, the through-pores may extend through both the semiconductor material layer as well as other layers. 
     According to an embodiment, the semiconductor cell culture device further comprises a plurality of sensors for analysis of a cell construct, wherein each of the plurality of sensors is arranged on an island structure and wherein sensor connections to the plurality of sensors are arranged on the bridge structures. 
     The semiconductor cell culture device provides island structures which are able to extend into the interior of a three-dimensional cell culture. By having sensors arranged on the island structures, the semiconductor cell culture device enables performing measurements and thereby analyzing the interior of a cell construct. 
     Thanks to the use of a semiconductor material layer in forming the cell culture portion, the cell culture device facilitates arranging sensors on island structures and providing connections to such sensors for control and read-out of measurements. 
     According to an embodiment, the plurality of sensors comprises at least one of: an electrode for detecting an electrical signal, a photosensitive area for detecting light or a piezoelectric sensor. 
     Sensors may be used in various ways for detecting different properties of a cell construct. The semiconductor cell culture device may comprise sensors of one or more types. Having sensors of different types may enable acquiring of various information relating to the cell construct. Having sensors of only a single type may reduce complexity of circuitry in the semiconductor cell culture device. 
     The sensors may include electrodes for detecting electrical signals. Thus, electrical signals propagating in the three-dimensional cell culture, spontaneously or as a response to stimulation, may be recorded. 
     The sensors may include photosensitive areas. This may be used for imaging an interior of the cell construct. 
     The sensors may include a piezoelectric sensor. This may be used for detecting e.g. changes in pressure, temperature or strain within the cell construct. 
     According to an embodiment, the semiconductor cell culture device further comprises a plurality of actuators for affecting a cell construct, wherein each of the plurality of actuators is arranged on an island structure and wherein actuator connections to the plurality of actuators are arranged on the bridge structures. 
     Actuators may be used for affecting the cell construct, such as for triggering a response from the cell construct that may be measured. Thus, actuators may for example include electrodes for providing a stimulation signal to the cell construct, whereby a response to the stimulation signal may be recorded. 
     The actuators may alternatively comprise light-emitting diodes or other light sources for illuminating the cell construct e.g. for imaging and/or for providing excitation light that may induce emission of light from the cell construct. A light source may be provided on an island structure. However, according to an alternative, the light source may be external to the cell culture portion and light may be guided through waveguides to the island structures, wherein light is emitted towards the cell construct. 
     The actuators may alternatively comprise a transducer for emitting a surface acoustic wave into the cell construct. This may be used for sensing mass and mechanical properties of the cell construct. 
     The actuators may alternatively comprise electrodes for electroporation of cells. Thus, cell permeability may be allowed and selective introduction of molecular payloads may be provided. 
     The actuators need not necessarily be used in combination with sensing or measuring of a response from the cell construct. Rather, the actuators may affect, such as mechanically affect, the cell construct, e.g. for controlling culturing of cells, without a response being measured. Thus, the semiconductor cell culture device may comprise actuators in combination with sensors, but the semiconductor cell culture device may alternatively only comprise actuators or only comprise sensors. 
     When actuators and sensors are provided, actuators and sensors may be arranged on common island structures or may be arranged on separate island structures. 
     According to an embodiment, the mesh structure has a regular pattern forming an array of island structures and an array of through-pores. 
     Such a mesh structure may be easy to manufacture as identical structures are to be formed in a pattern. The regular pattern may be suitable for a three-dimensional cell culture as through-pores which may be needed for the cell culture may be evenly distributed over an entire cell culture portion. 
     Further, the regular pattern may ensure that sensors and/or actuators may be arranged in a regular pattern to provide an even distribution of sensors and/or actuators. This enables the semiconductor cell culture device to provide sensing/actuation throughout a cell culture at the cell culture portion. 
     According to an embodiment, the island structures may have a maximum dimension of at least 5 μm, wherein the bridge structures may have a width of at least 5 μm and a length of at least 10 μm, wherein the area of the cell culture portion has a maximum dimension of at least 500 μm, wherein a thickness of the cell culture portion is at least 1 μm and wherein a thickness of the supporting structure is at least 1 μm. 
     Island structures may have varying geometric shapes, e.g. circular, rectangular, polygonal, or arbitrarily shaped. The island structures within a cell culture device may have identical or varying geometric shape. A dimension of an island structure may be defined as a largest distance between two positions on sides of the island structure (e.g. length of rectangle, diameter of circle, maximum axis of arbitrary shape). 
     According to an embodiment, the island structures may have a maximum dimension of at least 5 μm, 10 μm, 25 μm, 50 μm, 100 μm or 200 μm. The maximum dimension of the island structures may be selected based on a size of e.g. sensors and/or actuators to be arranged on the island structures. Also, the maximum dimension of the island structures may be selected based on desired flexibility and stability of the mesh structure. 
     Neighboring island structures may be connected by bridge structures. Bridge structures may also have varying geometric shapes, e.g. to follow differently shaped paths, which may be identical or varying within a cell culture device. Typically, a bridge structure may comprise a constant width (size in the plane of the semiconductor material layer perpendicular to a path along the bridge structure between two island structures). The bridge structure may extend along a straight path between two island structures, but may alternatively for example extend along a circular spiral path or a serpentine path. The bridge structure may be defined by the width and the length of the bridge structure between the two island structures. 
     According to an embodiment, the bridge structures may have a width of at least 5 μm, 10 μm, 15 μm, or 25 μm. The width of the bridge structures may be selected based on ensuring that wires for connections to sensors and/or actuators on the island structures may be arranged on the bridge structures. Also, the width of the bridge structures may be selected based on desired flexibility and stability of the mesh structure. 
     According to an embodiment, the bridge structures may have a length at least corresponding to a distance between two island structures. The length of the bridge structures may be at least 10 μm, 50 μm, 100 μm or 200 μm. The length of the bridge structures may be selected based on a distance between two island structures. The length of the bridge structures may also be selected based on desired flexibility and stability of the mesh structure, e.g. if a serpentine path of the bridge structure is used. 
     Through-pores may be defined as a spacing surrounded by a plurality of island structures and a plurality of bridge structures interconnecting the island structures. A through-pore may have varying geometric shapes, e.g. circular, square, polygonal or arbitrarily shaped. The through-pores within a cell culture device may have identical or varying geometric shape. A dimension of a through-pore may be defined as a largest distance between two positions on structures surrounding the through-pore (e.g. diameter of circle, side of square, maximum axis of arbitrary shape). 
     According to an embodiment, the through-pores may have a maximum dimension of less than 1 μm, 5 μm, 10 μm, 50 μm, 90 μm. The maximum dimension of the through-pores may be selected for controlling transport through the through-pores, such as to select a desired permeability of the cell culture portion. For example, the through-pores may have a maximum dimension of no more than 10 μm, such that cell soma are unable to pass but cell media and/or cellular neurites may pass the through-pores. According to an embodiment, the through-pores may have a maximum dimension of approximately 80 μm or in a range of 80-100 μm. This may be advantageous in enabling three-dimensional growth of neuronal cell constructs. The dimensions of the through-pores may also be selected based on desired flexibility and stability of the mesh structure. 
     An area of the cell culture portion may define an overall size of the cell culture portion for the three-dimensional cell culture. A maximum dimension of the cell culture portion may be defined as a largest distance between two positions on periphery of the cell culture portion (e.g. length of rectangle, diameter of circle, maximum axis of arbitrary shape). 
     According to an embodiment, the cell culture portion may have a maximum dimension of at least and/or no more than 500 μm, 1 mm, 2 mm, 3 mm, 5 mm, 10 mm or 100 mm. The dimension of the cell culture portion may be selected based on a desired area in which sensing and/or actuation of the three-dimensional cell culture is desired. The dimension of the cell culture portion may also be selected based on desired flexibility and stability of the mesh structure. 
     A thickness of the cell culture portion may define a thickness of the semiconductor material layer in the area of the cell culture portion. The thickness may be constant or varying in the cell culture portion. 
     According to an embodiment, the thickness of the cell culture portion is at least and/or no more than 1 μm, 5 μm, 10 μm, 15 μm, 17 μm, or 25 μm. The thickness of the cell culture portion may be selected based on function of transport of cell constructs, cellular components, proteins or other large molecules through the cell culture portion. The thickness of the cell culture portion may also be selected based on desired flexibility and stability of the mesh structure. 
     A thickness of the supporting structure may define a thickness of the semiconductor material layer and/or a structure attached to the semiconductor material layer. The supporting structure may be solid in a relatively large area, such that the supporting structure may provide support to the cell culture portion, even though the supporting structure need not necessarily be thicker than the cell culture portion. The thickness of the supporting structure may thus be smaller than, equal to, or larger than the thickness of the cell culture portion. 
     According to an embodiment, the thickness of the supporting structure is at least 1 μm, 10 μm, 50 μm, 100 μm, 300 μm, 400 μm, 500 μm, or 725 μm. The thickness of the supporting structure may be selected so as to provide stability to the semiconductor cell culture device. The thickness of the supporting structure may also be selected in order to provide a desired compactness of the semiconductor cell culture device. The thickness of the supporting structure may also be selected to provide a desired distance between the cell culture portion and another structure, such as another cell culture portion of another semiconductor cell culture device in a stack of cell culture devices. 
     According to an embodiment, the supporting structure is configured to surround the area of the cell culture portion. 
     Hence, a support may be provided surrounding the cell culture portion, which may be useful in ensuring a stability of the cell culture portion in the entire area of the cell culture portion. 
     According to an embodiment, a thickness of the supporting structure is larger than a thickness of the cell culture portion. 
     This implies that the supporting structure may provide a stable support to the cell culture portion. The thickness of the supporting structure may also define a distance between the cell culture portion and another structure. 
     According to an embodiment, grooves extending perpendicularly to a plane defined by the semiconductor material layer are arranged on sidewalls of island structures and/or sidewalls of bridge structures. 
     Growth of cells may be stimulated along the grooves. Thus, by arranging grooves on sidewalls of island structures and/or sidewalls of bridge structures, growth of cells extending along the through-pores may be stimulated. The grooves may further facilitate alignment of cells along the through-pores. 
     According to an embodiment, the semiconductor cell culture device further comprises at least one aperture through the semiconductor material layer adjacent to the cell culture portion for allowing forming of a wall of a culture space through the semiconductor material layer to form the wall around the cell culture portion. 
     Thus, a culture space may be formed surrounding the cell culture portion and extending on opposite sides of the semiconductor material layer in which the cell culture portion is defined. This may be useful in defining a confined space in which the three-dimensional cell culture is formed. 
     The culture space may be formed with open ends on both sides of the semiconductor material layer forming a tubular space or with a closed end at one side forming a well. 
     The forming of the culture space may be achieved e.g. through casting or injection molding of the wall through the at least one aperture. 
     The at least one aperture may comprise one aperture extending to enclose almost entirely the cell culture portion. However, in order to provide a strong connection between the semiconductor material layer on opposite sides of the at least one aperture, the semiconductor cell culture device may comprise a plurality of apertures, such that connections between the apertures for connecting the semiconductor material layer on opposite sides of the at least one aperture may be distributed along a circumference enclosing the cell culture portion. The at least one aperture may then have an arc shape. 
     According to an embodiment, the semiconductor cell culture device further comprises one or more apertures within or adjacent to the area of the cell culture portion, wherein the one or more apertures are configured for providing fluid flow to the cell construct. 
     Thus, the through-pores of the mesh structure may be used for providing a structure through which a cell construct may grow. This may be combined with the one or more apertures for providing flow of culture media or other fluids through the cell culture portion. 
     The one or more apertures may be of varying size. By selecting the size of the one or more apertures, fluid velocity and/or selective permeability of the apertures may be tuned. 
     The one or more apertures may be arranged within the mesh structure or adjacent to the mesh structure. For instance, the one or more apertures may be arranged inside an area defined by a wall of a culture space that may be formed through the semiconductor material layer. 
     According to a second aspect, there is provided a system for three-dimensional cell culture, comprising a plurality of semiconductor cell culture devices according to the first aspect, wherein the semiconductor cell culture devices are stacked such that the cell culture portion of a first semiconductor cell culture device of the plurality of semiconductor cell culture devices is arranged above a second semiconductor cell culture device of the plurality of semiconductor cell culture devices. 
     Effects and features of this second aspect are largely analogous to those described above in connection with the first aspect. Embodiments mentioned in relation to the first aspect are largely compatible with the second aspect. 
     Thanks to stacking of semiconductor cell culture devices, several planes through a three-dimensional cell culture may be defined. This may be useful in controlling growth of a three-dimensional cell culture. Further, if the semiconductor cell culture devices are provided with sensors and/or actuators, sensing and/or actuation of the three-dimensional cell culture may be provided in several planes extending through the three-dimensional cell culture. 
     According to an embodiment, the semiconductor cell culture devices are stacked by the supporting structure of the first semiconductor cell culture device being arranged on the supporting structure of the second cell culture device such that a distance is provided between the cell culture portion of the first semiconductor cell culture device and the cell culture portion of the second semiconductor cell culture device. 
     Thus, the supporting structures of the semiconductor cell culture devices may be used for defining distances between the cell culture portions. It should be realized that the supporting structure of the first semiconductor cell culture device being arranged on the supporting structure of the second semiconductor cell culture device does not necessarily imply that the supporting structure of the first semiconductor cell culture device is directly on the supporting structure of the second semiconductor cell culture device. Rather, one or more other layers may be arranged there-between. 
     According to an embodiment, the semiconductor cell culture devices comprise electrodes on the island structures and wherein connections to the electrodes are provided through independent bond pads of each of the semiconductor cell culture devices. 
     Hence, electronic circuitry (sensors and/or actuators) on each semiconductor cell culture device may be independently connected to external circuitry. The external circuitry may be provided in form of a printed circuit board that may provide circuitry for controlling sensors and/or actuators and/or for read-out and processing of information acquired by the sensors. 
     According to another embodiment, the semiconductor cell culture devices comprise electrodes on island structures and wherein a first semiconductor cell culture device is wire bonded to a second semiconductor cell culture device which is connected to external circuitry for connecting the electrodes on the first semiconductor cell culture device to the external circuitry. Thus, connections between an external circuitry and the semiconductor cell culture devices may be shared. 
     According to another embodiment, the semiconductor cell culture devices comprise electrodes on the island structures and wherein a through-substrate via is provided in at least one of the semiconductor cell culture devices for electrically connecting the semiconductor cell culture device to another semiconductor cell culture device for sharing a bond pad. 
     In this embodiment, it is required to form connections between the layers of different semiconductor cell culture devices. However, then it may be sufficient to connect the semiconductor cell culture devices through a single bond pad to external circuitry. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above, as well as additional objects, features and advantages of the present inventive concept, will be better understood through the following illustrative and non-limiting detailed description, with reference to the appended drawings. In the drawings like reference numerals will be used for like elements unless stated otherwise. 
         FIG. 1  is a schematic cross-sectional view of a semiconductor cell culture device according to an embodiment. 
         FIG. 2  is a schematic view illustrating a mesh structure of a semiconductor cell culture device. 
         FIGS. 3 a - d    are schematic views illustrating different embodiments of mesh structures. 
         FIG. 4  is a schematic view of a detail of a mesh structure. 
         FIG. 5  is a schematic perspective view of a semiconductor cell culture device according to an embodiment. 
         FIG. 6  is a schematic view illustrating use of a semiconductor cell culture device within a culture space. 
         FIGS. 7 a - d    are schematic views illustrating manufacture of a semiconductor cell culture device. 
         FIG. 8  is a schematic view illustrating a system comprising a plurality of semiconductor cell culture devices according to an embodiment. 
         FIG. 9  is a schematic view of the system according to another embodiment. 
         FIG. 10  is a schematic view illustrating an embodiment of the mesh structure. 
         FIG. 11  is a schematic view of the system according to another embodiment. 
         FIG. 12  is a schematic view of the semiconductor cell culture device according to another embodiment. 
         FIG. 13  is a schematic view of the semiconductor cell culture device according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , a semiconductor cell culture device  100  according to an embodiment will be described. The semiconductor cell culture device  100  comprises a cell culture portion  110  in a layer  102  of semiconductor material. The cell culture portion  110  comprises a mesh structure  112 , having through-pores  114  allowing for selective transport of cell constructs, cellular components, proteins or other large molecules through the layer  102 . Thanks to the through-pores  114 , the semiconductor cell culture device  100  may be used for three-dimensional cell culture, wherein the cell culture portion  110  extends within the interior of a cell construct. 
     The semiconductor cell culture device  100  may be used for growth of three-dimensional cell cultures. For instance, the mesh structure  112  of the semiconductor cell culture device  100  may have a particular shape and/or may have particular dimensions of the through-pores  114  such that the three-dimensional cell culture may be controlled. Therefore, the semiconductor cell culture device  100  may be useful as such for three-dimensional cell culture. 
     Thanks to forming the cell culture portion  110  and mesh structure  112  in a semiconductor material, the mesh structure  112  may be formed with accurate control of minute structures using semiconductor manufacturing technology. For instance, the layer  102  of semiconductor material may be a silicon layer, such as using a silicon wafer. 
     Further, thanks to defining the cell culture portion  110  with the mesh structure  112  in a semiconductor material, the semiconductor cell culture device  100  facilitates providing sensors and/or actuators in the mesh structure  112  such that sensors and/or actuators extending into the interior of a three-dimensional cell culture may be provided. Hereinafter, the semiconductor cell culture device  100  will be described mainly in relation to having sensors and/or actuators arranged in the mesh structure  112 . 
     The semiconductor cell culture device  100  may further comprise a supporting structure  120 . The supporting structure  120  may be formed as a solid portion of the layer  102  of the semiconductor material so as to provide support for the cell culture portion  110  and the mesh structure  112 . The supporting structure  120  may alternatively or additionally be formed by a structure being attached to the layer  102  of the semiconductor material. The mesh structure  112  may, by means of the through-pores  114 , be highly flexible and may need the supporting structure  120  as support of the highly flexible surface. 
     As shown in  FIG. 1 , the supporting structure  120  may have a first portion  120   a  and a second portion  120   b , arranged at different sides of an area of the cell culture portion  110  in the layer  102  of semiconductor material. The supporting structure  120  may be formed by a portion of the layer  102  having a larger thickness than a thickness of the cell culture portion  110 , even though it should be understood that the thickness of the supporting structure  120  may be equal to or even less than the thickness of the cell culture portion  110 . 
     Referring now to  FIG. 2 , the mesh structure  112  according to an embodiment will be described in further detail. 
     The mesh structure  112  may comprise island structures  116  interconnected by bridge structures  118 . The island structures  116  and the bridge structures  118  are formed in the layer  102  of semiconductor material. The island structures  116  may together with the bridge structures  118  surround through-pores  114  and therefore define dimensions of the through-pores  114 . 
     The island structures  116 , bridge structures  118  and through-pores  114  there-between may be formed in many different shapes and dimensions. For instance, size and shapes of the through-pores  114 , the island structures  116 , and the bridge structures  118  may be designed in relation to selective permeability of the mesh structure  112  (i.e. which type of substances, cells, or cellular components should be allowed to pass the mesh structure  112 ), and desired stability and flexibility of the mesh structure  112 . 
     The mesh structure  112  may provide a regular pattern, wherein the through-pores  114 , island structures  116 , and bridge structures  118  are evenly distributed within the mesh structure  112 . This may provide a regular arrangement of sensors  130  and/or actuators  132  on the island structures  116 . However, the mesh structure  112  may alternatively have different sizes of the structures in different portions of the mesh structure  112 . 
     The semiconductor cell culture device  100  may be provided with sensors  130  and/or actuators  132  arranged on the island structures  116 . These sensors  130  and/or actuators  132  may include various types. The mesh structure  112  may further provide connections  134  to the sensors  130  and/or actuators  132  arranged on the bridge structures  116  so as to allow control from and/or transfer of signals to circuitry arranged external to the mesh structure  112 . The connections  134  may comprise wires for transferring electrical signals, but may in some embodiments also or alternatively comprise waveguides for transferring an electromagnetic wave, such as light. 
     The sensors  130  may include electrodes for detecting electrical signals. Thus, electrical signals propagating in the three-dimensional cell culture, spontaneously or as a response to stimulation, may be recorded. 
     The sensors  130  may include photosensitive areas. This may be used for imaging an interior of the cell construct. 
     The sensors  130  may include a piezoelectric sensor. This may be used for detecting e.g. changes in pressure, temperature or strain within the cell construct. 
     The actuators  132  may include active electrodes for providing a stimulation signal to the cell construct. 
     The actuators  132  may include a light source for illuminating the cell construct. The light source may be arranged at the island structure  116 . Alternatively, the cell construct may be illuminated by the actuator  132  including a light output coupler from a waveguide that transfers light to the island structure  116 . 
     The actuators  132  may include a transducer for emitting a surface acoustic wave into the cell construct. This may be used for sensing mass and mechanical properties of the cell construct. 
     Referring now to  FIGS. 3 a - d   , some alternative embodiments of mesh structures  112  are illustrated. It should be realized that the mesh structure  112  may be further designed in various other ways. 
       FIG. 3 a    illustrates the same structure as shown in  FIG. 2 , wherein the mesh structure  112  has square-shaped island structures  116  with straight bridge structures  118 . Each island structure  116  is connected to four neighboring island structures  116 . 
       FIG. 3 b    illustrates hexagonal island structures  116  with straight bridge structures  118 , wherein each island structure  116  is connected to six neighboring island structures  116 . 
       FIG. 3 c    illustrates a centrally arranged island structure  116  being connected to a circular spiral path defined by the bridge structure  118 . The bridge structure  118  allows a flexibility for transforming the shape of the mesh structure  112 . 
       FIG. 3 d    illustrates a centrally arranged island structure  116  connected to a serpentine shaped path defined by the bridge structure  118 . The bridge structure  118  also allows a flexibility for transforming the shape of the mesh structure  112 . 
     Referring now to  FIG. 4 , shapes of sidewalls of island structures  116  and bridge structures  118  are illustrated. The sidewalls may be provided with grooves  119  that extend perpendicularly to the plane of the layer  102  of semiconductor material. Thus, the grooves  119  may extend along a direction of through-pores  114 . 
     The grooves  119  may facilitate cellular alignment along the grooves  119  which may be useful in ensuring a desired cell growth in the cell culture portion  112 . 
     The sidewalls may be straight such that a cross-section of the through-pores  114  may be constant through the thickness of the layer  102  of semiconductor material. However, the sidewalls may alternatively be sloped such that the through-pores  114  may have an increasing or decreasing size of the cross-section through the thickness of the layer  102 . 
     Referring now to  FIG. 5 , further structures may be formed in the layer  102  of semiconductor material. As illustrated in  FIG. 5 , the semiconductor cell culture device  100  may comprise a plurality of arc-shaped apertures  140 . The arc-shaped apertures  140  may be used for forming a wall of a culture space through the semiconductor material. Thus, the semiconductor cell culture device  100  facilitates forming a wall around the cell culture portion  110  to form e.g. a tubing or a well in which cell culture may take place. 
     The arc-shaped apertures  140  may be configured to substantially enclose the cell culture portion  110  to facilitate that a wall of the culture space is formed enclosing the cell culture portion  110  therein. However, the arc-shaped apertures  140  may still provide a connection in the semiconductor material on opposite sides of the apertures  140  between the cell culture portion  110  and semiconductor material that will be arranged outside the culture space. This ensures stability of the shape of the semiconductor cell culture device  100  before the wall of the culture space is formed. In order to facilitate a stability of the shape of the device  100 , a plurality of arc-shaped apertures  140  are preferably provided. 
     It should be realized that the apertures  140  may have another shape depending on a desired cross-sectional shape of the culture space. 
     The wall may be formed through the layer  102  of semiconductor material, e.g. by a castable or injectable material being molded through the apertures  140 . 
     As further illustrated in  FIG. 5 , the semiconductor cell culture device  100  may further comprise one or more fluid-flow apertures  142  through the layer  102  of semiconductor material. The fluid-flow apertures  142  may be arranged within the mesh structure  112  as particular apertures  142  which may have different shape or otherwise different properties than the through-pores  114 . The fluid-flow apertures  142  may alternatively or additionally be arranged adjacent to the mesh structure  112 , e.g. within an area enclosed by a wall of the culture space. 
     The one or more fluid-flow apertures  142  may provide flow of culture media or other fluids through the layer  102  of semiconductor material. 
     The one or more fluid-flow apertures  142  may be of varying size. By selecting the size of the one or more fluid-flow apertures  142 , fluid velocity and/or selective permeability of the fluid-flow apertures  142  may be tuned. 
     Referring now to  FIG. 6 , the semiconductor cell culture device  100  is illustrated with a culture well  150  having an open end  152  at a first end above the cell culture portion  110  and a closed end  154  at a second end below the cell culture portion  110 . 
     The culture well  150  may define a confined space in which cell culture takes place. The cell culture portion  110  is configured to extend through the confined space and thus enables sensing and/or actuation of interior of a cell construct that is cultured in the culture well  150 . 
     Referring now to  FIGS. 7 a - d   , a method of manufacturing of a semiconductor cell culture device  100  will be briefly discussed. The method should serve to illustrate one way of manufacturing the semiconductor cell culture device  100 , and it should be realized that the semiconductor cell culture device  100  may be manufactured in different manners as will be appreciated by a person skilled in the art. 
     As illustrated in  FIG. 7 a   , the semiconductor cell culture device  100  may be formed as a silicon on insulator structure. Hence, a semiconductor substrate  202 , e.g. silicon, may be provided with a dielectric layer  204 , e.g. SiO 2 . 
     First, a layer  102  of semiconductor material may be formed on the dielectric layer  204 . The thickness of the layer  102  may be selected in dependence of a desired thickness of the cell culture portion  110 . 
     Then, dielectric layers  206  with metal patterns  208  and connections between different metal layers may be formed on the layer  102 . Electrodes  210  may also be formed on a top surface. 
     As illustrated in  FIG. 7 b   , removing of dielectric material to form connections to bond pads  212  may then be performed. Then, selective removal of material may be performed to form a mesh structure  112  through the dielectric layers  206 , the semiconductor layer  102  and the dielectric layer  204 , e.g. by deep silicon etching from a front side of the device. Hence, the mesh structure  112  may be defined on the semiconductor substrate  202 . 
     As illustrated in  FIG. 7 c   , a sacrificial material may then be deposited extending into the mesh structure  112 . Then, the semiconductor substrate  202  may be removed at least in the area of the cell culture portion  110 . The semiconductor substrate  202  may be removed from a back side of the device, e.g. by first generally thinning the entire semiconductor substrate  202 , e.g. stopping at a desired thickness of the supporting structure  120 . Then, the semiconductor substrate material may be selectively removed in the area of the cell culture portion, e.g. by deep silicon etching. 
     Finally, as illustrated in  FIG. 7 d   , the sacrificial material may be removed and the structure may be attached to a dicing tape for dicing and packaging. 
     In an embodiment, the semiconductor cell culture device  100  is provided with electrodes  210 . The electrodes  210  may for instance be passive electrodes. 
     The semiconductor cell culture device  100  may be provided with 1, 2 or more electrodes  210  per island structure  116 . 
     The electrodes  210  may be of varying sizes and shapes. For instance, the electrodes  210  may be square, circular or arbitrarily shaped having a maximum dimension of 5 μm, 10 μm, 20 μm, 25 μm or 50 μm. The electrodes  210  may for instance be formed by tungsten, platinum, platinum-iridium alloys, iridium oxide, titanium nitride and/or poly(ethylenedioxythiophene) (PEDOT). 
     The connections to the electrodes  210  may be formed by wires or traces extending on the bridge structures  118 . For instance, 1, 2 or more connections may be formed on a bridge structure  118 . The connections may for instance be formed by copper, aluminum, or gold and may be formed in varying sizes and shapes. 
     Portions of electrodes  210  and connections may need to be insulated from the cell culture. Insulation may be achieved by a passivation layer being added, such as a layer of silicon nitride, silicon dioxide and/or insulating resists. 
     The semiconductor cell culture device  100  may further be provided with reference electrodes. Reference electrodes may be provided in the mesh structure  112 , such as having a plurality of reference electrodes arranged in the mesh structure  112 , e.g. on selected island structures  116 . 
     Alternatively, reference electrodes may be provided adjacent to the cell culture portion  110  within the culture space  150 . As a further alternative, reference electrodes may be arranged externally to the semiconductor cell culture device  100  and may be connected to external circuitry to which the semiconductor cell culture device  100  is also connected. 
     Referring now to  FIG. 8 , a system  300  for three-dimensional cell culture will be described. 
     As illustrated in  FIG. 8 , a plurality of semiconductor cell culture devices  100  may be stacked on top of each other. A wall of a culture space  350  may be formed through all of the semiconductor cell culture devices  100  to define a culture space extending through all the cell culture portions  110 . This implies that a plurality of cell culture portions  110  extending through different planes of the culture space  350  may be provided. 
     Thus, the system  300  may provide sensing and/or actuation distributed in three dimensions extending through the interior of a cell construct  360 . Hence, the system  300  enables detailed information relating to three-dimensional cell constructs  360  to be acquired. 
     The semiconductor cell culture devices  100  may be stacked by the supporting structures  120  being arranged on top of each other. 
     When several semiconductor cell culture devices  100  are stacked such that fluid is allowed to flow across all layers defined by the semiconductor cell culture devices  100 , a conformable layer may be arranged between the semiconductor cell culture devices  100 . 
     The semiconductor cell culture devices  100  may for instance be integrated by direct silicon-silicon bonding, by means of a polydimethylsiloxane (PDMS) membrane, a bio-compatible silicone, a bio-compatible epoxy or bio-compatible double-sided adhesive. 
     Each semiconductor cell culture device  100  may have independent contacts  370  to external circuitry, e.g. in the form of bond pads. The semiconductor cell culture devices  100  may thus comprise self-contained sensors  130  and/or actuators  132  with associated connections and may be independently bonded to e.g. an external printed circuit board. 
     However, according to an alternative, the semiconductor cell culture devices  100  may be provided with electrical interconnections. For instance, through-substrate vias may be provided for electrically integrating the semiconductor cell culture devices  100 . Then, the semiconductor cell culture devices  100  may share a common bond pad which may be connected to external circuitry, e.g. an external printed circuit board. 
     According to yet another alternative, the semiconductor cell culture devices  100  may be wire bonded to each other in the stack such that a first semiconductor cell culture device may be wire bonded to a second semiconductor cell culture device which may in turn be wire bonded to a third semiconductor cell culture device and so forth until one semiconductor cell culture device is connected to the external circuitry. 
     The semiconductor cell culture devices  100  may have contacts  370  for connection to external circuitry arranged outside the culture space  350 . Thus, connections from the mesh structure  112  may be routed to outside the culture space  350  and the contacts  370  may be arranged outside the culture space  350  in which fluid flow is provided. 
     Referring now to  FIG. 9 , an alternative embodiment of the system  300  is shown. As illustrated in  FIG. 9 , the culture space  350  may be provided with additional inlets  352  and/or outlets  354  between the semiconductor cell culture devices  100 . Thus, additional fluid flow into or out of portions of the culture space  350  between the semiconductor cell culture devices  100  may be provided. 
     Referring now to  FIGS. 10-13 , some additional variations of the semiconductor cell culture device  100  and the system  300  will be illustrated and discussed. 
     In  FIG. 10 , an example of a highly compliant mesh structure  112  is illustrated. This may be beneficial in particular applications of cell culture. 
     The island structure  116  and bridge structures  118  illustrated in  FIG. 10  are designed to an effective stiffness of approximately 6 kPa, which is on the same order of magnitude of stiffness of brain tissue. 
     Referring now to  FIG. 11 , the supporting structure  120  is formed by a thin flexible material. For instance, a thin organic flexible material such as polyimide may be used. 
     The mesh structures  112  may be connected at sides of the mesh structure to the flexible material for providing the supporting structure  120 . Further, electrical connections to the mesh structures  112  may be provided by means of conductors  136  provided on a surface of the flexible material. 
     The conductors  136  may be patterned on the mesh structure  112  being connected on the surface of the flexible material. The conductors  136  may be provided with an open end to allow further connection to e.g. a wire bond. 
     The use of the thin flexible material may allow mesh structures  112  to be packed very closely together, such as spaced apart by 20-50 μm. This allows for high resolution of sensors  130  and/or actuators  132  in a direction perpendicular to the mesh structure  112 . 
     Stacking of the supporting structures  120  of flexible material may be provided by gluing or clamping supporting structures  120  together. 
     Referring now to  FIG. 12 , the semiconductor cell culture device  100  may be provided with a supporting structure  120  only at one side of an area of the cell culture portion  112 . Instead of defining a culture space in which the cell culture portion  112  is arranged, the cell culture portion  112  may extend from the supporting structure  120  in a cantilever-type arrangement to extend into a three-dimensional cell culture  360 . 
     The three-dimensional cell culture  360  may extend on opposite sides of the cell culture portion  110  but may also extend to surround an end of the layer  102  of semiconductor material layer. 
     The cell culture portion  110  may thus probe into the three-dimensional cell culture, which may be used for analysis into interior of cell constructs, without the cell constructs necessarily being confined in a particular culture space. 
     A plurality of probes may be used in different positions in relation to a three-dimensional cell culture for enabling sensing and/or actuation in three dimensions. 
     Referring now to  FIG. 13 , the semiconductor cell culture device  100  may be configured such that the layer  102  of semiconductor material does not necessarily extend in a plane. Rather, the layer  102  may be transformed into another desired shape extending in three dimensions, which may be used e.g. for stimulating a particular growth of a cell construct. Thus, the cell culture portion  110  may extend in three dimensions. 
     For instance, as illustrated in  FIG. 13 , the layer  102  may assume a helical shape, which may be useful in controlling a desired shape of a cell construct. 
     In the above the inventive concept has mainly been described with reference to a limited number of examples. However, as is readily appreciated by a person skilled in the art, other examples than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended claims.