TABLE I.

Comparison of different droplet generation methods.

Droplet generation technology	Advantages	Disadvantages
Microfluidic method	1. High throughput (1 k–87 kHz, 1–8 channels)	1. Difficult to isolate single droplet, no position control
	2. Large liquid viscosity range	2. Dedicate fabrication of chip
	3. Control of droplet volume
	4. Low dead volume
	5. Good biocompatibility
Commercial DOD inkjet printing	1. High throughput (1 k–20 k Hz, 3–6 channels)	1. Low biocompatibility for thermal inkjet printing
	2. Direct operation on single droplet with position/composition control	2. High cost of cartridge, need of wash
		3. Limited viscosity range (dynamic viscosity: 2–30 cp for DMP; less than 20 cp for Microfab)
		4. Large dead volume
Piezoelectric microfluidic impact printing	1. Multiple channels expandability (4–12 channels)	1. Low frequency: less than 200 Hz
	2. Direct operation on single droplet with position/composition control	2. Limited viscosity range (dynamic viscosity < 14 cp)
	3. Low-cost and disposable cartridge
	4. Control of droplet volume
	5. Low dead volume
	6. Good biocompatibility