Fig. 2

Measurement of clot contraction and stiffening in the microclot array. Schematic diagram (a) and phase contrast and fluorescence (b) sideview images of a microtissue before and after platelet-mediated contraction. Micropillar deflection (δ1 and δ2) can be easily detected after platelet adhesion and activation (postflow), which was used to calculate microclot-generated contractile force. Comparison of microtissue contractile force (c) and fluorescence intensity (d) before and after platelet flow. e Schematic diagram of microtissues before and after externally applied stretching. Mechanical stretching caused microtissue elongation (d2–d1), which was used to calculate tensile strain; the force needed to develop such elongation was reported by micropillar deflection as F = k(δ1′ + δ2′)/2 which was used to calculate the tensile stress. Microtissue stiffness was determined based on stress−strain relationship. f Comparison of tissue elongation between a microclot and a bare collagen microtissue under the same amount of substrate stretch. g Comparison of the stiffness between microclots and bare collagen microtissues. *P < 0.001, n > 10, each dot in box plot represents an independent experiment. All box plots with whiskers represent the data distribution based on five number summary (maximum, third quartile, median, first quartile, minimum). Statistical significance was determined by unpaired t test with Welch’s correction method. Scale bar is 200 µm