**3. Cell interrogation platform**

OERM is being integrated in a biosensing platform. The platform's objective is to achieve effective drug screening at the single cell level. The platform has mainly two parts as shown in Figure 5: one is reconfigurable delivery and the other is cell interrogation. In the reconfig‐ urable delivery area, cells, drugs and molecules are prepared and supplied to the cell inter‐ rogation area by the reconfigurable microchannel. In the cell interrogation area, cells area attached on the substrate and plasmonic sensors are placed around cells to detect bio‐markers from cells under drug stimulation.

To realize the platform, two different temperature conditions have to be realized in the platform. The reconfigurable delivery needs low temperature condition to keep working materials frozen. On the other hand, a high temperature condition (e.g. 37 ◦C) has to be kept in the cell interrogation part to keep cells alive. It is also important to supply drugs from reconfigurable microchannel. The flow from the reconfigurable microchannel has to be controlled to supply drugs to cells efficiently. This section presents mainly these two issues: temperature control and flow control for the cell interrogation platform.

**Figure 6.** Experimental setup for temperature measurement on the thermoelectric devices

**Table 1.** Temperature measurement on the thermoelectric devices

**Measurement point Temperature [◦C]** 1 12 2 1 3 -6 4 -4 5 9 6 30 7 38 8 36

System Integration of a Novel Cell Interrogation Platform 307

The temperature variation has to be small to form uniform microchannels in the reconfigura‐ ble area. To check the temperature distributions on the platform, the simulation was conduct‐ ed using a finite element analysis method. At first, the platform was directly put on the two thermoelectriccoolerstocheckthetemperatureuniformityontheplatforminthissimplesetting. Figure 7 (a) shows the constructed model. Two thermoelectric coolers are placed with some distance to projectlight patterns onto the platform in between the coolers. The platform is made of glass, and the thermoelectric coolers and room temperature are set to ‐5 ◦C and 20 ◦C respectively. The thermal conductivity of the glass substrate was set to 0.74 W/(m K) in the simulation. The simulation result is shown in Figure 7 (b). In this condition, the temperature variation on the glass substrate is large and the temperature cannot maintain below 0 ◦C in the reconfigurable area.Inthis experimental setup,ice cannotbe formedonthe reconfigurable area.

#### **3.1. Temperature control**

In the cell interrogation platform, water (or culture media) is used as a working media of the reconfigurable microchannel for cell transportation. It is important to realize the temperature on the reconfigurable area below 0 ◦C to keep ice. On the other hand, temperature has to be kept at 37 ◦C to culture cells in the cell interrogation area. Thermoelectric devices are used to realize these two temperature conditions in the small platform.

Atfirst,two thermoelectric devices area were used to check whetherthese devices can maintain desired temperatures. Thermoelectric devices are widely used to control temperature below 0 ◦C in a small area such as a few square millimeters [11, 12]. Thermoelectric devices have also been integrated in microfluidic devices to control temperature for microvalves operation [13], making ice in a microchannel [14], and DNA analysis [15]. Figure 6 shows the experimental setup of the thermoelectric devices. The thermoelectric cooler has a heat sink and a fan on the warm side to cool down the warm side and achieve low temperature on the cold side. A glass slide was placed on the thermoelectric devices to check the temperature on the substrate. The temperature on the glass substrate was measured by an infrared thermometer. 8 points as shown in Figure 6 were measured in this experiment. In the experiment, 12 V and 2.3 V were applied to the thermoelectric cooler and heater respectively. Table 1 shows the results. On the cooler, the temperature was below 0 ◦C and frosts grew on the cooler and the glass substrate. On the heater, the temperature showed around 37 C. The results indicate that the thermo‐ electric devices can be used to control temperature on the cell interrogation platform.

**Figure 6.** Experimental setup for temperature measurement on the thermoelectric devices


**Table 1.** Temperature measurement on the thermoelectric devices

**3. Cell interrogation platform**

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306

from cells under drug stimulation.

**3.1. Temperature control**

OERM is being integrated in a biosensing platform. The platform's objective is to achieve effective drug screening at the single cell level. The platform has mainly two parts as shown in Figure 5: one is reconfigurable delivery and the other is cell interrogation. In the reconfig‐ urable delivery area, cells, drugs and molecules are prepared and supplied to the cell inter‐ rogation area by the reconfigurable microchannel. In the cell interrogation area, cells area attached on the substrate and plasmonic sensors are placed around cells to detect bio‐markers

Micro-Nano Mechatronics — New Trends in Material, Measurement, Control, Manufacturing and Their Applications in

To realize the platform, two different temperature conditions have to be realized in the platform. The reconfigurable delivery needs low temperature condition to keep working materials frozen. On the other hand, a high temperature condition (e.g. 37 ◦C) has to be kept in the cell interrogation part to keep cells alive. It is also important to supply drugs from reconfigurable microchannel. The flow from the reconfigurable microchannel has to be controlled to supply drugs to cells efficiently. This section presents mainly these two issues:

In the cell interrogation platform, water (or culture media) is used as a working media of the reconfigurable microchannel for cell transportation. It is important to realize the temperature on the reconfigurable area below 0 ◦C to keep ice. On the other hand, temperature has to be kept at 37 ◦C to culture cells in the cell interrogation area. Thermoelectric devices are used to

Atfirst,two thermoelectric devices area were used to check whetherthese devices can maintain desired temperatures. Thermoelectric devices are widely used to control temperature below 0 ◦C in a small area such as a few square millimeters [11, 12]. Thermoelectric devices have also been integrated in microfluidic devices to control temperature for microvalves operation [13], making ice in a microchannel [14], and DNA analysis [15]. Figure 6 shows the experimental setup of the thermoelectric devices. The thermoelectric cooler has a heat sink and a fan on the warm side to cool down the warm side and achieve low temperature on the cold side. A glass slide was placed on the thermoelectric devices to check the temperature on the substrate. The temperature on the glass substrate was measured by an infrared thermometer. 8 points as shown in Figure 6 were measured in this experiment. In the experiment, 12 V and 2.3 V were applied to the thermoelectric cooler and heater respectively. Table 1 shows the results. On the cooler, the temperature was below 0 ◦C and frosts grew on the cooler and the glass substrate. On the heater, the temperature showed around 37 C. The results indicate that the thermo‐

electric devices can be used to control temperature on the cell interrogation platform.

temperature control and flow control for the cell interrogation platform.

realize these two temperature conditions in the small platform.

The temperature variation has to be small to form uniform microchannels in the reconfigura‐ ble area. To check the temperature distributions on the platform, the simulation was conduct‐ ed using a finite element analysis method. At first, the platform was directly put on the two thermoelectriccoolerstocheckthetemperatureuniformityontheplatforminthissimplesetting. Figure 7 (a) shows the constructed model. Two thermoelectric coolers are placed with some distance to projectlight patterns onto the platform in between the coolers. The platform is made of glass, and the thermoelectric coolers and room temperature are set to ‐5 ◦C and 20 ◦C respectively. The thermal conductivity of the glass substrate was set to 0.74 W/(m K) in the simulation. The simulation result is shown in Figure 7 (b). In this condition, the temperature variation on the glass substrate is large and the temperature cannot maintain below 0 ◦C in the reconfigurable area.Inthis experimental setup,ice cannotbe formedonthe reconfigurable area.

**Figure 7.** Simulation results when the platform is directly placed on the two thermoelectric cooler (a) A schematic of constructed model for the simulation (b) Simulation result.

To realize low temperature (below 0 ◦C) and small variation ofthe temperature on the platform, an aluminium plate was placed in between the thermoelectric coolers and the platform. Figure 8 (a) shows the constructed model. The aluminium has high thermal conductivity (225 W/(m K)). The aluminium plate can be cooled by the thermoelectric coolers precisely and fast. The aluminium plate has a 7 mm × 7 mm square hole to project light images from underneath onto the reconfigurable area. The platform can be cooled strongly because the bottom face of the platform can be attached to the aluminium plate outside of the reconfigurable area. As shown in Figure 8 (b) and (c), the temperature in the reconfigurable area was maintained below 0 ◦C and the temperature variation was less than 0.7 ◦C. This result indicates that the aluminium plate is effective for cooling.

**Figure 8.** Simulation results when an aluminium plate was paced in between the cooler and platform (a) A schematic of constructed model (b) Simulation result (c) Temperature variation in the reconfigurable area (temperature on the

System Integration of a Novel Cell Interrogation Platform 309

**Figure 9.** Simulation results when an acrylic bar was paced under the reconfigurable area (a) A schematic of con‐ structed model (b) Simulation result (c) Temperature variation in the reconfigurable area (temperature on the red

red dash line in (b))

dash line in (b))

For practical uses of this cooling system, condensation of the vapour is one of the significant problems. Light patterns from the DMD device come from underneath of the reconfigurable area. If there is condensation water on the platform, the light pattern is refracted by the condensation and the light pattern is changed. To prevent condensation on the platform, an acrylic baris placed on the path of the light pattern from the DMD device to the reconfigurable area. Acrylic materials have low thermal conductivity (0.19 W/(m K)) and it is considered that the bottom face of the acrylic bar can be maintained close to the room temperature even if the top face is under 0 C provided that the acrylic baris long enough. In the simulation, the acrylic bar is placed in and under the hole of aluminium plate as shown in Figure 9 (a). The height of the acrylic bar was set on 35 mm.

Figure 9 (b) and (c) shows the simulation results. The temperature in the reconfigurable area is kept under 0 C and the temperature variation decreased to less than 0.3 C. On the other hand, the bottom face of the acrylic bar is more than 18 C. The results show that the uniform low temperature in the reconfigure area can be realized and condensation under the recon‐ figurable area can be prevented by putting the acrylic bar under the reconfigurable area.

**Figure 7.** Simulation results when the platform is directly placed on the two thermoelectric cooler (a) A schematic of

Micro-Nano Mechatronics — New Trends in Material, Measurement, Control, Manufacturing and Their Applications in

To realize low temperature (below 0 ◦C) and small variation ofthe temperature on the platform, an aluminium plate was placed in between the thermoelectric coolers and the platform. Figure 8 (a) shows the constructed model. The aluminium has high thermal conductivity (225 W/(m K)). The aluminium plate can be cooled by the thermoelectric coolers precisely and fast. The aluminium plate has a 7 mm × 7 mm square hole to project light images from underneath onto the reconfigurable area. The platform can be cooled strongly because the bottom face of the platform can be attached to the aluminium plate outside of the reconfigurable area. As shown in Figure 8 (b) and (c), the temperature in the reconfigurable area was maintained below 0 ◦C and the temperature variation was less than 0.7 ◦C. This result indicates that the aluminium

For practical uses of this cooling system, condensation of the vapour is one of the significant problems. Light patterns from the DMD device come from underneath of the reconfigurable area. If there is condensation water on the platform, the light pattern is refracted by the condensation and the light pattern is changed. To prevent condensation on the platform, an acrylic baris placed on the path of the light pattern from the DMD device to the reconfigurable area. Acrylic materials have low thermal conductivity (0.19 W/(m K)) and it is considered that the bottom face of the acrylic bar can be maintained close to the room temperature even if the top face is under 0 C provided that the acrylic baris long enough. In the simulation, the acrylic bar is placed in and under the hole of aluminium plate as shown in Figure 9 (a). The height of

Figure 9 (b) and (c) shows the simulation results. The temperature in the reconfigurable area is kept under 0 C and the temperature variation decreased to less than 0.3 C. On the other hand, the bottom face of the acrylic bar is more than 18 C. The results show that the uniform low temperature in the reconfigure area can be realized and condensation under the recon‐ figurable area can be prevented by putting the acrylic bar under the reconfigurable area.

constructed model for the simulation (b) Simulation result.

plate is effective for cooling.

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the acrylic bar was set on 35 mm.

**Figure 8.** Simulation results when an aluminium plate was paced in between the cooler and platform (a) A schematic of constructed model (b) Simulation result (c) Temperature variation in the reconfigurable area (temperature on the red dash line in (b))

**Figure 9.** Simulation results when an acrylic bar was paced under the reconfigurable area (a) A schematic of con‐ structed model (b) Simulation result (c) Temperature variation in the reconfigurable area (temperature on the red dash line in (b))

A thermoelectric heater is added in the model to realize cell interrogation area in the platform. Fig. 10 (a) shows the constructed model. the thermoelectric heater and coolers are set on 37 C and ‐5 C respectively. The distance between the coolers and heater were set on 10 mm.

which reached 5 when the flow rate was set on 1000 μl/min. It is considered that the spread

System Integration of a Novel Cell Interrogation Platform 311

To check the spread of cells by discharging from the microchannel, RAW 264.7 macrophage cells were used. Cell analysis has been achieved in microfluidic devices previously [16]. The glass substrate was coated by poly‐L‐lysine to attach cells on the substrate before experiment [18]. Polylysine is commonly used to improve cell adhesion on substrates and can be used to make arrays of cells and hydrogels for biological application [18, 19]. In the experiment, the cells were discharged from the microchannel in 5 minutes by the flow rate of 1000 μl/min. Figure 12 shows the experimentalresult. The cells were discharged from the microchannel and spread on the substrate. The spread angle of cells was large compared to the flow experiment as shown in Figure 3.7. When the syringe pump was stopped, the flow was not suddenly stopped but gradually slowed down. During the slowdown of the flow speed, the cells were spread throughout the substrate. It is expected that the cells not attached to the substrate can be flush out by a solution without cells when the patterning of the substrate is conducted to

angle is small enough to supply cells and drugs to the target position in the platform.

**Figure 11.** Observation results of spread angle when the flow rate was changed from 700 to 1000 μl/min.

attach cells partially before experiment.

**Figure 10.** Simulation results when the thermoelectric coolers and heater are integrated for the platform. (a) A sche‐ matic of constructed model (b) Simulation result (c) Temperature variation in the reconfigurable area (temperature on the red line in (b))

The simulation results shows that the reconfigurable area is kept under 0 C even if the heater is added.

#### **3.2. Flow control**

To realize the cell interrogation platform as shown in Figure 5, cells, drugs and molecules for cell interrogation have to be supplied from reconfigurable delivery area. To supply cells and drugs to the cell interrogation area efficiently, the spread angle of the flow from the reconfig‐ urable area has to be small. To check the relationship in between the flow rate and the spread angle, a polydimetylsiloxane (PDMS) microchannel was used. The cross‐sectional shape of the microchannel is about 200 μm×100 μm. In the experiment, flow rate was changed from 700 μl/ min to 1000 μl/min by a syringe pump. To check the spread angle, blue dyed water flowed out from the microchannel and the outlet of the microchannel was observed under a microscope.

Figure 11 shows the experimental results. Blue‐dyed water flowed out from the PDMS microchannel to the open space. The spread angle decreased when the flow rate increased, which reached 5 when the flow rate was set on 1000 μl/min. It is considered that the spread angle is small enough to supply cells and drugs to the target position in the platform.

A thermoelectric heater is added in the model to realize cell interrogation area in the platform. Fig. 10 (a) shows the constructed model. the thermoelectric heater and coolers are set on 37 C and ‐5 C respectively. The distance between the coolers and heater were set on 10 mm.

Micro-Nano Mechatronics — New Trends in Material, Measurement, Control, Manufacturing and Their Applications in

**Figure 10.** Simulation results when the thermoelectric coolers and heater are integrated for the platform. (a) A sche‐ matic of constructed model (b) Simulation result (c) Temperature variation in the reconfigurable area (temperature on

The simulation results shows that the reconfigurable area is kept under 0 C even if the heater

To realize the cell interrogation platform as shown in Figure 5, cells, drugs and molecules for cell interrogation have to be supplied from reconfigurable delivery area. To supply cells and drugs to the cell interrogation area efficiently, the spread angle of the flow from the reconfig‐ urable area has to be small. To check the relationship in between the flow rate and the spread angle, a polydimetylsiloxane (PDMS) microchannel was used. The cross‐sectional shape of the microchannel is about 200 μm×100 μm. In the experiment, flow rate was changed from 700 μl/ min to 1000 μl/min by a syringe pump. To check the spread angle, blue dyed water flowed out from the microchannel and the outlet of the microchannel was observed under a microscope. Figure 11 shows the experimental results. Blue‐dyed water flowed out from the PDMS microchannel to the open space. The spread angle decreased when the flow rate increased,

the red line in (b))

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310

**3.2. Flow control**

is added.

To check the spread of cells by discharging from the microchannel, RAW 264.7 macrophage cells were used. Cell analysis has been achieved in microfluidic devices previously [16]. The glass substrate was coated by poly‐L‐lysine to attach cells on the substrate before experiment [18]. Polylysine is commonly used to improve cell adhesion on substrates and can be used to make arrays of cells and hydrogels for biological application [18, 19]. In the experiment, the cells were discharged from the microchannel in 5 minutes by the flow rate of 1000 μl/min. Figure 12 shows the experimentalresult. The cells were discharged from the microchannel and spread on the substrate. The spread angle of cells was large compared to the flow experiment as shown in Figure 3.7. When the syringe pump was stopped, the flow was not suddenly stopped but gradually slowed down. During the slowdown of the flow speed, the cells were spread throughout the substrate. It is expected that the cells not attached to the substrate can be flush out by a solution without cells when the patterning of the substrate is conducted to attach cells partially before experiment.

**Figure 11.** Observation results of spread angle when the flow rate was changed from 700 to 1000 μl/min.

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**Figure 12.** Discharge of macrophages from the microchannel
