In this paper, we propose a microfluidic device capable of generating a retarding flow field for the sorting and separation of human motile sperm in a high-throughput manner. The proposed sorting/separation process begins with a rapid flow field in a straight-flow zone to carry sperm into a sorting zone to maintain the sperm's mobility. The sorting zone consists of a diffuser-type sperm sorter to differentiate sperm with different motilities based on the flowing upstream nature of human sperm in a retarding flow field. The dead sperm will then be separated from the live ones by passing through a dumbbell flow field to the outlet for disposal. The proposed flowing upstream sperm sorter (FUSS) is designed to imitate the selection mechanism found in the female body when sperm swim into the uterus. The experimental results demonstrate the utility of this device with regard to throughput (approximately 200 000 sperm per minute and a maximum of 200 million cells per mL), efficiency (90% of selected sperm are mobile), and the ability to select sperm with high motility (∼20% of sperm with a velocity exceeding 120 μm s). The proposed device is suitable for intrauterine insemination as well as in vitro fertilization thanks to the highly efficient sorting process not interfering with the natural function and energy resource of human sperm.

The 3GPP WCDMA is a widely accepted third-generation cellular system standard. By using nonorthogonal codes for different users, the multiple access interference (MAI) can be a limiting factor for system performance, as for other CDMA systems. Multiuser detection (MUD) is known to reduce MAI and improve CDMA system performance, but many such techniques have high complexity. Successive interference cancellation (SIC) is an effective MUD technique with relatively low complexity. We consider the software implementation of an SIC receiver for WCDMA uplink transmission on a commercially available general-purpose multi digital signal processor (DSP) platform. This also goes in line with the recent interest in software-defined radio. Issues addressed in this work include job partitioning and signal routing for multiprocessor implementation, design of SIC components (especially the channel estimator and the signal regenerator), determination of the precision of fixed-point computations, consideration of the receiver's error performance and analysis of the implementation's complexity and efficiency. These issues are tightly coupled with the 3GPP WCDMA specifications. Because the employed platform only contains four DSPs, the implementation only considers up to three users. But this is sufficient for us to appreciate various DSP implementation issues of an SIC receiver. Moreover, by the nature of SIC, it is easy to extend the implementation to handle more users with an enlarged platform. Our present implementation achieves real-time speed in the RAKE receiver part of the complete receiver. Due to the complexity in signal regeneration, the overall SIC receiver still falls short of the real-time requirement when interference cancellation is activated. In fact, the platform employed presently cannot support real-time processing when the number of multipaths is four or more, unless either the system architecture or the SIC algorithm is redesigned. Such and other ways of improvement are relegated to potential future work.