A spacer configured to be received in a stacked assembly between a membrane and a surface so that the surface, spacer, and membrane are stacked in a first direction, the spacer configured to be received in the stacked assembly so as to provide a volume for fluid flow between the membrane and the surface in a second direction transverse to the first direction, the spacer comprising: a plurality of baffles interconnected together; a body formed at least in part by the plurality of baffles , the body having a thickness direction (T) oriented in the first direction when the spacer is received in the stacked assembly; a plurality of openings arranged between interconnected baffles in the thickness direction (T) that permit fluid flow through the plurality of openings when fluid flows through the stacked assembly in the second direction, wherein the plurality of openings extend through the body in the thickness direction (T) and boundaries of the plurality of openings are formed at least in part by baffles of the plurality of baffles ; and a plurality of joints interconnecting at least some of the baffles of the plurality of baffles , wherein the plurality of baffles and joints includes one or more passages that permits fluid flow through the respective baffle or joint when fluid flows through the stacked assembly in the second direction, wherein the one or more passages are arranged through a cross-section of the body , the one or more passages of the plurality of baffles are disposed within and through a respective baffle of the plurality of baffles , and the one or more passages of the plurality of joints are disposed within and through a respective joint of the plurality of joints , wherein the body further includes the plurality of joints , wherein the plurality of joints are larger in the thickness direction (T) than the plurality of baffles , wherein boundaries of each of the plurality of openings are formed by four baffles of the plurality of baffles and four joints of the plurality of joints , and wherein one or more baffles of the plurality of baffles has at least a portion having a helical shape or has a rod-like shape. a plurality of baffles interconnected together; a body formed at least in part by the plurality of baffles , the body having a thickness direction (T) oriented in the first direction when the spacer is received in the stacked assembly; a plurality of openings arranged between interconnected baffles in the thickness direction (T) that permit fluid flow through the plurality of openings when fluid flows through the stacked assembly in the second direction, wherein the plurality of openings extend through the body in the thickness direction (T) and boundaries of the plurality of openings are formed at least in part by baffles of the plurality of baffles ; and a plurality of joints interconnecting at least some of the baffles of the plurality of baffles , wherein the plurality of baffles and joints includes one or more passages that permits fluid flow through the respective baffle or joint when fluid flows through the stacked assembly in the second direction, wherein the one or more passages are arranged through a cross-section of the body , the one or more passages of the plurality of baffles are disposed within and through a respective baffle of the plurality of baffles , and the one or more passages of the plurality of joints are disposed within and through a respective joint of the plurality of joints , wherein the body further includes the plurality of joints , wherein the plurality of joints are larger in the thickness direction (T) than the plurality of baffles , wherein boundaries of each of the plurality of openings are formed by four baffles of the plurality of baffles and four joints of the plurality of joints , and wherein one or more baffles of the plurality of baffles has at least a portion having a helical shape or has a rod-like shape. <EOS>