In this paper, we propose a freeze tweezer using the freezing force of a small volume of nucleotide ice to manipulate mini/micro objects in an aqueous state. Several prototypes of such a device based on the Joule-Thompson throttling effect have been fabricated and there have been preliminary demonstrations of their applicability in manipulating a wide variety of objects. By regulating the freezing conditions of the cooler, an ice ball can be formed between the tweezer tip and the object it contacts and then the object can be picked up. This freezing force is strong enough to manipulate objects with any shape, electric charge, light or heavy, biological or non-living, on the condition that the contact area can be frozen. Successful manipulation of a series of specific objects presented in this paper indicates that it would be much easier for the freeze tweezer to handle objects with smaller size. Therefore, further nanoscale freeze tweezers following the same idea as above can be put forward; this is expected to have exciting applications in micro/nano engineering field. Furthermore, theoretical analysis and experiments have been performed to quantify the response time of the freeze tweezer and the mechanical force generated on the tweezer tip. This study has also raised quite a few new fundamental issues related to the fabrication and practices of the freeze tweezer.

This paper is aimed at comprehensively investigating the dynamic low-frequency electrical impedance (DLFI) of biological materials during the processes of freezing, thawing and heating, and combinations of them. Electrical impedance detection (EID) was proposed as a means of rapidly evaluating the viability of biological materials subject to freezing or thermal injury (processes expected to be significant in the practices of cryobiology and hyperthermia). Using two experimental setups, the DLFI for selected biological materials (fresh pork and fish) under various freezing and heating conditions was systematically measured and analyzed. Preliminary results demonstrate that damage that occurs to a biological material due to freezing or heating could result in a significant deviation in its electric impedance value from that of undamaged biomaterials. Monitoring impedance change ratios under various freezing and heating conditions may offer an alternative strategy for assessing the amount of damage sustained by biomaterials subject to cryosurgery, cryopreservation and hyperthermia. Implementation of the present method in order to develop a new micro-analysis or biochip system is also suggested.

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