## 1 Introduction  
Sampling and elution are the very first steps in the preparation of biochemical assays, which are used in the clinical testing or analysis of environmental samples. Swabs are widely used to collect biological samples, such as saliva, nasal sputum, semen, blood, or urine from the human body. They are made of cotton, rayon, polyurethane foam, or polyester, and are available in a spun or flocked tipped format. Cotton based collection methods are the most widely used sample collection techniques with salivary or sputum based immunoassay because of its easy availability, low cost and high absorbance. Apart from biological samples, swabing techniques are also used for DNA analysis of touched evidence [1], recovery of spores from environmental surfaces [2; 3], or the removal of dried blood stains [4]. Depending on the field of application, the type of swab used could vary (dry and pre-moistened swabs [1], or macrofoam swabs [2]). Recovery of samples from these swab tips requires a stable and high efficiency elution technique, and the success rate of all the downstream processes, like lysis and DNA amplification, are governed by the number of captured and lysed cell. The concentration of microbial cells in body fluids has a significant influence on diagnostic sensitivity of any assay. The concentration of pathogens can range from 1 \(\times\) 10\({}^{4}\) CFU/mL in nasal sputum samples of nosocomial pneumonia patients [5] to 1.6 \(\times\) 10\({}^{9}\) CFU/mL in the saliva of periodontitis patients [6]. Apart from these common body fluids, samples from blood, vaginal fluid, urinary tracts, or semen are also collected by swabs [7; 8]. Sperm cell recovery is a critical for elution in sexual assault samples of forensic cases. Recovery efficiency of spermatozoa, as low as 10% [8], collected from a victim's body hinders the subsequent process of lysis and PCR amplification, thereby incorrectly characterizing the sample as negative to sperms. Higher recovery is essential for cases where trace amounts of bacterial cells are available in the body fluids. Several methods have been used to increase the recovery of the sample constituents from the swab. Among them, chemically enhanced recovery [8; 9; 10] and water extraction techniques involving vortexing [2; 3] are the most common techniques for elution and recovery of sperm cells. Enzymatic dissolution of cotton fibres result in 18-23% recovery [8], which could be increased when detergents like Sarkosyl (54.4%) and sodium dodecyl sulfate (SDS) (78.50%) were used [9]. Vortexing can be used for the recovery of bacterial spores in environmental samples from cotton, macrofoam, polyester, and rayon swabs, with an average recovery of 6.6% and 26.7% for dry and pre-moistened swabs, respectively [3]. Sometimes, convective flow has been associated with vortexing to enhance the recovery (41.7%) of _Bacillus anthrac_ spores [2; 3]. A comparative performance by [PERSON] et al. [11] for extraction of _Staphylococcus aureus_ from metal surfaces with abrasive techniques showed an apparent recovery efficiency of 18% for electrostatic wipes, 10% for roller sampler and 0.04% for contact plates, which are lesser than those that were obtained from ultrasonic elution processes (32.1%) [12; 13; 14]. Another widely used process is the thermal elution technique [13; 15; 16], which possess the added advantage of eluting and lysing the cells simultaneously. Mechanical and magnetophoretic agitation methods require higher volumes or a continuous flow of eluent and highly intricate systems for detecting the target analyte to yield a maximum of only 55% recovery. Several swabbing devices have also been reported in the patent literature. These devices use periodic vibration or compressible forces for elution. For example, a swab analyser with a porous swabing pen was designed by [PERSON] et al. [17], which utilises 5 mL of eluent flow for the removal of immunological components taken from skin and pharyngeal cavity. [PERSON] et al.