NOVELTY - An apparatus for symmetrically stirred laminar flows, comprises a pair of opposite planar surfaces, each having a series of dual-chevron grooves; a flow cell formed with microfluidic channel for supporting at least one fluid laminar flow in a principal direction. The microfluidic channel is formed between planar surfaces. The groove has a first orientation that forms an angle relative to the principal directions formed between a pair of opposing planar surfaces.    USE - In laminar flow fuel cell for symmetrically stirred laminar flows and for increasing rates of mass transfer to reactive boundary surfaces (claimed); and in microfluidic system.    ADVANTAGE - The apparatus provides increased rates of mass transfer at the boundary layers in proximity to the electrodes and other benefits over current membraneless mixing cell structures. The apparatus controls mass transport limitations to electrodes which can result in a high performance, micro-integrated fuel cell (e.g., hydrogen/oxygen). The apparatus generates higher currents, greater power and increases fuel efficiencies. The apparatus generates localized disturbances in the flow within the fuel or fluid cell structure such that increased rates of mass transfer can be achieved locally without global mixing, which is an important consideration and often undesired in membraneless fuel cell apparatus. The series of grooved surfaces formed along each opposing side of the electrode or boundary walls within the flow cells promote symmetrical stirring and are passive structures. There are no moving parts required for such cells provided in the apparatus which greatly simplifies related operational and manufacturing processes.    DETAILED DESCRIPTION - An apparatus for symmetrically stirred laminar flows comprises a flow cell formed with at least one microfluidic channel for supporting at least one fluid laminar flow in a principal direction, where the microfluidic channel is formed between a pair of opposing planar surfaces each having at least one symmetrical groove along a plane of symmetry running substantially parallel with opposing planar surfaces. The groove has a first orientation that forms an angle relative to the principal directions formed between a pair of opposing planar surfaces. The symmetrical groove is a round bottomed or flat bottomed groove. The opposing planar surfaces include a first series of chevron-shaped grooves formed with two apex points to provide dual or double chevron-shaped structures. The apparatus further comprises a second series of non-identical chevron-shaped grooves relative to the first series on the opposing planar surfaces having formed with two apex points; a membrane positioned within the flow cell separating the microfluidic channel into two compartments to sustain separate symmetrically stirred laminar flows within each of the two compartments. INDEPENDENT CLAIMS are included for the following:    (1) a laminar flow fuel cell comprising a pair of electrodes each formed with a planar surface facing each other that defines a channel between electrodes, where each opposing channel surface has chevron-shaped protrusions formed in at least a portion of the channel surface so that each chevron-shaped groove or protrusion has at least one apex that defines an angle; and    (2) increasing rates of mass transfer to reactive boundary surfaces involving providing the flow cell structure; and directing two co-flowing fluids to flow along the opposing surfaces thereby forming a diffusive membrane between the fluids so that diffusion can occur as between the two co-flowing fluids, where each fluid flowing adjacent to an opposing surface has a Reynolds number that is less than 100, and at least a portion of the co-flowing fluids are stirred luminary in a direction substantially transverse relative to the principal direction.    DESCRIPTION OF DRAWING(S) - The figure shows a co-flowing laminar streams in a planar membraneless microfluidic fuel cell.