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Persona & ClearPlan development


Unilever’s leading pregnancy test business Unipath wished to develop a home-use diagnostic system for the prediction of women’s fertility. The objective was to have products for use either as conception aids or as natural family planning aids. Unipath needed a low-cost instrument which could be mass-produced and used by the general public - a major challenge for a clinical diagnostic system.


Cambridge Consultants used its fundamental knowledge of low-cost opto-electronic systems to guide the overall system from the very early stages of feasibility. The traditional approach of using lasers, expensive imaging optics and stepper motors to scan test-strips was clearly not going to meet the cost targets so we set about defining a way in which low-cost LEDs and unlensed photodiode arrays could do the job.


We developed a non-imaging optical sensor which was robust against ambient light and variations in the test-strip geometry. Clever use of analog signal processing in a custom mixed signal ASIC allowed us to create a fully ratiometric measurement system which could self-calibrate the sensor and further reduce variability in the measurement due to manufacturing tolerances.

We designed and built laboratory instruments based upon the core sensor technology which allowed Unipath to develop the test-strip while we turned our attention to the consumer product.

We implemented the electronics for the instruments using a custom mixed signal ASIC and a low-cost microcontroller. External components were kept to a minimum in order to minimise cost and protect Unipath’s valuable intellectual property.

We used our relationships with major electronic manufacturers to identify a suitable facility for making a medical grade consumer product and carried out the transfer of the design into volume production.

Following the successful launch of Persona in Europe, we carried out a complete redesign of the external packaging of the product and added a smart-card interface for collecting clinical data. The resulting product was launched as ClearPlan Easy in the USA and won a Medical Design Excellence Award.


Unipath was a hugely successful assay and diagnostic development company but without expertise in instrumentation. By collaborating with Cambridge Consultants, they were able to develop a product family at a price-point which seemed infeasible at the outset of the program.

Persona and ClearPlan Easy were world first products in the field of natural family planning. Clear-Plan Easy dominates the market in the USA as a sophisticated and reliable aid to predict fertility and hence aid conception. Unilever sold Unipath to one of the world’s leading diagnostic companies, Alere, and they have gone on to further develop the strong brand.