# Development and validation of a sperm-freezing device created using 3D printer technology

## TL;DR

This paper presents a 3D-printed device for freezing semen straws that provides consistent and reproducible cooling conditions.

## Contribution

The novel contribution is a 3D-printed prototype that enables safe and reproducible sperm freezing with consistent results.

## Key findings

- The 3D-printed device produced highly reproducible temperature cooling curves.
- The device withstood over 300 freezing cycles without damage.
- Sperm recovery rates were consistent regardless of straw position or support type.

## Abstract

To develop and evaluate the effectiveness of a 3D-printed prototype to hold
semen straws during the freezing process under safe and reproducible
conditions.

A prototype capable of holding ten straws in liquid nitrogen vapor (LN2) was
3D printed. A second support that is commonly used was assembled from pieces
of expanded polyethylene (EPS), respecting the identical distance between
the straws and the LN2 surface. Temperatures were registered with a
thermocouple placed inside a straw. Semen samples were frozen in the
presence of cryoprotectant using the prototype (n=20) and the EPS support
(n=20) in two independent series of measurements. Sperm parameters
(motility, vitality, and DNA fragmentation) were measured for fresh and
frozen-thawed samples.

The temperature cooling curves measured on the prototype were remarkably
reproducible. The prototype material withstood over 300 freezing cycles
without damage. The mean motility and vitality of fresh (64.2%, 72.0%) and
frozen-thawed (25.7%, 38.8%) samples were significantly different
(p<0.001) using either support. Recovery rates of
motility, vitality, and sperm DNA fragmentation in frozen-thawed sperm
samples were equal regardless of straw position on the prototype or support
type used.

The developed device allows a homogeneous, quantifiable, reproducible cooling
of the straws in liquid nitrogen vapor. The recovery rates are comparable to
those reported in the literature for both tested supports. The designed 3-D
printed prototype favors the safe handling of the straws, an explicit way of
describing freezing conditions, and a better intra-operator and
inter-laboratory reproducibility of the cryopreservation process.