‘Big advantages to remove micro-organisms from semen’

In artificial insemination, used in the porcine and bovine industry, biosecurity and the elimination of antibiotics are important issues. ‘Microfluidic separation techniques may be more proficient in the future than macroscale separation techniques,’ Tanja Hamacher believes. ‘Here the working mechanisms are at the cellular range, using the size differences between micro-organisms and spermatozoa.’

Two kinds of microfluidic separation devices have been explored to improve semen samples in pigs and cows: pinched flow fractionation (PFF) and acoustophoresis. ‘The bacteria removal and sperm recovery rates were both very high,’ Tanja says.

The viability decrease of the porcine spermatozoa was small but significant in the PFF device. ‘We expected this outcome, due to shear stresses and the sensitivity of porcine spermatozoa,’ Tanja says.

The decisive preference for the acoustophoresis device had another reason however, she explains. ‘Here more improvements are available to increase the sample throughput in future devices, to achieve the desired processing time one day,’ she says. ‘Our suggestions are: increasing the sample concentration and flow rate; optimizing the chip design; using hypo-osmotic swelling (HOS) solutions; and finally, parallelizing several devices.’      


The type of work Tanja Hamacher performed in this PhD project was experimental in nature. ‘Because of my background as a biomedical-engineer this suited me very well,’ she says. ‘One of the highlights was the collaboration with the Swedish based company AcouSort. I was happy to use their up-to-date devices and chips. I performed experiments in Sweden under the guidance of experts, using their expertise and knowledge of industrial settings.’


The collaboration with AcouSort resulted from a workweek in Denmark in which various companies from Sweden and Denmark were involved.

‘The expertise of the Bios lab-on-a-chip Group was welcomed there,’ Tanja says. ‘We could make a fruitful research proposal in which the experience and research results of my promotors, professors Loes Segerink and Albert van den Berg, was of obvious added value. I am glad my work is taken further in a follow-up PhD project, as the results are really promising now.’


During her project, Tanja collaborated with the Mesa+ Biomolecular Nanotechnology (BNT) Group.

Tanja: ‘Their expertise on preparing my samples with the cowpea viruses was crucial. The size of these viruses are very well within the scope of my research, in the range up to 500 nanometers. Above that, the BNT-lab has high experience in preparing these viruses, which can be used in a safe and well-labelled way in contrast to most other virus types. This kind of complementing skills and facilities, is a big advantage of the Mesa+ institution I strongly believe.’  


In her future job Tanja aims at a research job, close to application and market-ready devices in the medical field. ‘I prefer to work for a SME of approximately 50 to 60 employees,’ Tanja says. ‘I am looking forward to work on real innovations. I think the chance is present to find an interesting job to use my talents in the Netherlands, who knows even in Twente.’