# Dry Test Methods for Micropumps
## 1 Introduction  
The development of high throughput and low-cost testing methods and equipment for MEMS-based products has become a strategic topic to penetrate the consumer market. In addition, the Design-for-Testability approach is of great interest to reduce the cost of the test and to enable a built-in self-test where applicable. Due to the complexity of MEMS structures compared to ICs, the cost of the test in production can represent up to 30% of the end product price [1; 2; 3; 4]. MEMS devices exploit multiple domains (electrical, chemical, optical, mechanical, thermal, biological, fluidic, etc.) that require the development of specific test methods [5]. Depending on the production yield, tests are performed at different stages: at the wafer level (e.g., Electrical Wafer Sorting) using Automatic Test Equipment (ATE), after singulation and wire bonding, or after packaging to verify the overall device functionality. The goal of this approach is to reject a defective device in the earliest stage because the packaging of MEMS often represents 50% of the total manufacturing costs [3; 4; 5]. During the final test of MEMS in production, physical, electrical, or any other stimuli are submitted to the system, and the device output is monitored to determine conformity to product requirements and to calibrate some key parameters. The test strategy is based on the analysis of the key output parameters and the failure modes of the device [5; 6; 7]. MEMS inertial sensors are, for instance, submitted to an acceleration that is representative of their use in the field (low-g consumer applications or high-g automotive domain). Zero-g level and sensor sensitivity are also calibrated during the test. RF MEMS devices require spectrum analyzers connected to a probe station [8; 9]. The self-functional test of piezoresistive pressure sensors consist of the generation of the mechanical stimuli to the sensor membrane through a pneumatic actuation [10]. The air inside the pressure sensor cavity is heated by Joule effect that results from the generation of an electrical pulse to a resistor. BioMEMS, which refers, in its wider acceptance, to any biomedical device that is partly or fully made using any microfabrication process and which therefore has at least one micrometric or submicrometric feature, presents difficulties related to risks of contaminationand loss of sterility during the postproduction tests. Examples of bioMEMS devices include micropumps, lab-on-a-chip, organ-on-a-chip, DNA microarray, chemical sensor array, retina array, neuroMEMS, cell chips, droplet sorting devices using Electro-conjugate Fluid micropumps, etc. [11; 12; 13]. A BioMEMS for drug delivery should ideally be tested with a liquid to evaluate the effectiveness of the device. However, this method, which is difficult to implement and costly due to interconnection, drying, pollution, and sterility issues, can often be considered destructive except if the liquid remains in the system. In implantable applications, when the cost of the test does not matter, the pumping device can be filled near to capacity with sterile water and tested in production. This method was used by Medtronic for Synchromed II, the most implanted device in the USA for pain and spasticity [14; 15]. So, one of the first end-user operations is to empty the reservoir before the transfer of the drug into the pump reservoir. This procedure is cumbersome and impacts the concentration of the drug due to the presence of some residual sterile water in the reservoir. Priming the pump in production may also be considered if the system is not self-priming, but this option is costly and requires specific storage conditions. In addition, a device prefilled with a drug or biologic is a combination product regulated as a medicinal product [16]. This option has therefore an important impact on the time-to-market and the development cost.