## 2 Materials and Methods  
### Experimental Setup for Plasma Separation and Viscosity Measurement  
To separate the plasma from the suspended blood and sequentially measure the individual viscosities of blood and plasma, as shown in Figure 1A, plasma separation and quantification of blood flow were suggested. Figure 1(A-i) shows a schematic of the experimental setup, including a microfluidic device, ultrasonic transducer, two pumps (i.e., micro pump for blood and syringe pump for reference fluid), and microscopic image acquisition system. The microfluidic device was composed of two inlets (a, b), a blood channel (BC, width = 200 \(\upmu\)m), a reference fluid channel (RC, width = 200 \(\upmu\)m), a co-flowing channel (CC, width = 400 \(\upmu\)m), and an outlet. The depth of all the channels was fixed at 50 \(\upmu\)m. Based on the protocol reported in a previous study [22], a polydimethylsiloxane (Sylgard 184, Dow Corning, Midland, MI, USA) microfluidic device was fabricated using the soft lithography technique. To stabilize the pulsatile blood flows generated by the micropump, an air damper was connected to inlet (a) [29]. The air damper was embodied by clamping the open end of polyethylene tubing (i.d. = 500 \(\upmu\)m, length = \(L_{t}\)) with a steel pin. An ultrasonic transducer was used to separate the plasma from the suspended blood.  
By turning on an ultrasonic transducer, the primary radiation force contributes to moving disaggregated RBCs to nodes or anti-nodes of pressure fields depending on sign of acoustic correction factor (i.e., \(\phi>0\): node, \(\phi<0\): anti-node). Next, secondary radiation force and Bernoulli force induce to aggregate RBCs continuously. When gravity force of aggregated RBCs is greater than buoyant force, RBCs sedimentation begins. Plasma is then separated from the suspended blood inside the transducer [22]. Based on a previous study [22], frequency (\(f\)) and acoustic power (AP) were set to \(f=2.1\) MHz and AP = 2 watt, respectively. Suspended blood (\(\sim\)5 mL) was loaded into the ultrasonic chamber. A micropump (MP6, Bartels Mikrotechnik, Emil-Figge, Germany) was used to supply blood from the transducer to the inlet (a) of the microfluidic device. The flow rate of the micropump was adjusted by setting two parameters (frequency: \(f\), voltage: \(v\)) on a controller ([PERSON], Bartels Mikrotechnik, Emil-Figge, Germany). According to the viscosity measurement technique using the co-flowing method [13; 22], the viscosity and flow rate of the reference fluid should be specified in advance. Here, \(1\times\) PBS (Phosphate-Buffered Saline) was selected as the reference fluid, and the flow rate was set to 1 mL/h using a syringe pump (neMESYS, Cetoni GmbH, Korbussen, Germany). The microfluidic device was mounted on an inverted optical microscope (IX53, Olympus, Shinjuku, Tokyo, Japan) equipped with a \(10\times\) objective lens (N.A. = 0.25). To quantify the blood flow in the blood channel, microscopic images were captured using a high-speed camera (FASTCAM MINI, Photron, Tokyo, Japan). It was set to 5000 frames per second, and two microscopic images were sequentially captured, with an external trigger, at intervals of 1 s during all the experiments. Figure 1(A-ii) shows plasma separation within the ultrasonic transducer. Suspended blood was prepared by adding normal red blood cells (RBCs) to autologous plasma, and the Hct was set to 50%. As the ultrasonic standing wave contributed to accelerating RBC sedimentation in the transducer, the plasma volume (or height) increased significantly with time (i.e., \(t_{1}=t_{0}\), \(t_{2}=t_{0}+10\) min, \(t_{3}=t_{0}+10\) min, and \(t_{4}=t_{0}+10\) min).