O ver the past decade, embedded digital electronics have proliferated in both number and variety. Applications such as cellular phones, portable multimedia devices, and sensor networks have kept pace with dramatic increases in computing power and functionality. Battery technology, however, has not. Batteries limit the operating lifetime of portable devices and add undesirable weight and volume. They can't store sufficient energy to support longlifetime embedded applications such as monitoring civil infrastructure or studying the environment. Their replacement cost poses a major barrier to scaling wireless sensor networks to hundreds or thousands of nodes.Energy harvesting from human or environmental sources is a promising alternative to address these limitations and open new frontiers for integrating digital computation with sensing and actuation. Several alternative energy harvesting paradigms are possible, as either a substitute or a complement for batteries. The commercial sector has adopted mechanical energy harvesting as a redundant power source. Products already on the market include radios, flash-lights, and cell-phone chargers powered by handcranked electrical generators or shake-to-recharge electronics. But these mechanisms aren't suitable for all applications: first, they have low energy and power densities; second, they require active user involvement.Researchers have explored various passive energy-harvesting power sources for portable or wearable devices. These include gravity-driven and vibration-driven electromagnetic generators, piezoelectric shoe inserts, and thermocouples for harvesting energy from human body thermal gradients. Passive power sources for sensor networks, another target area for energy harvesting, 1 include ambient mechanical vibration. One project, which some of us worked on, developed a MEMS variable-capacitor transducer and accompanying chips that could harvest machine vibrations for sensor signal processing. 2 Despite a promising start, energy harvesting is still in its infancy. For current sensor network nodes, vibration-based energy harvesting allows an RF transmit duty cycle of less than 3 percent, excluding any computation that occurs at the transmitter. 1 Communication typically dominates power consumption, so many applications must maximize the computation done at a particular node. 3 Required off-chip power electronics can increase system cost and volume, and AC/DC conversion losses can limit energy-harvesting operation. Energy harvesting from human or environmental sources shows promise as an alternative to battery power for embedded digital electronics.Digital signal processors that harvest power from ambient mechanical vibration are particularly promising for sensor networks.

Passive energy harvesting from mechanical vibration has wide application in wearable and embedded sensors to complement or replace batteries. Energy harvesting efficiency can be increased by eliminating AC/DC conversion. A test chip demonstrating self-timing, power-on-reset circuitry, and memory for energy harvesting AC voltages has been designed in 180 nm CMOS and tested. Circuit operation is confirmed for supply frequencies between 60 Hz and 1 kHz with power consumption below 130 µW.

The recent explosion in capability of embedded and portable electronics has not been matched by battery technology. The slow growth of battery energy density has limited device lifetime and added weight and volume. Passive energy harvesting from vibration has potentially wide application in wearable and embedded sensors to complement or replace batteries. We propose increasing energy harvesting efficiency by eliminating AC/DC conversion electronics. We investigated self-timed circuits, power-on-reset circuitry and memory for energy harvesting AC power supplies. Our power-on-reset circuit achieves a substantial improvement over conventional approaches with 4.1 nW of simulated power dissipation and frequency-independent turn-on voltage. A chip is being fabricated to test the circuits presented here.

Background This study addresses the efficacy of an automated decontamination protocol using the germicide ‘tetra acetyl ethylene diamine (TAED) perborate’ (Farmec SpA, Italy). The germicide TAED perborate protocol is used in the Castellini Dental Units fitted with an Autosteril unit (an automated device that can cycle 0.26% TAED perborate solution and sterile water for cleaning the water system between patients and overnight). Prior to testing the Autosteril and the 0.26% TAED perborate protocol on the Logos Jr Dental Unit (Castellini SpA, Italy), TAED perborate was used on a dental unit water system simulation device. Methods A dental unit water system simulation device equipped with four dental unit water systems and with naturally grown and mature biofilm contamination was used in this study (three treatment units and one control). One treatment group used a simulated 5 minutes contact with TAED perborate and sterile water for irrigation; the second used a simulated 5 minutes contact with TAED perborate and 2 ppm ClO2 for irrigation; the third used a simulated 5 minutes contact with TAED perborate and municipal water for irrigation. The control group used municipal water for irrigation with no cleaning/disinfection protocols. This protocol was repeated for 30 cycles. Laser scanning confocal microscopy (LSCM) was used to study the effects on natural and mature biofilms, and R2A agar used to quantify heterotrophic plate counts in the effluent irrigant. Antimicrobial efficacy was evaluated by challenging TAED perborate with microbes and spores (M. smegmatis and B. subtilis). Deleterious effects of the germicide were evaluated on metal and nonmetal parts of dental unit water systems. Heterotrophic plate counts using R2A agar and LSCM of the lines were conducted to assess biofilm and microbial control. Results Baseline water samples showed mean contamination >5.6 log10 cfu/ml. After initial cleaning, all three groups maintained mean contamination levels of less than 1.1 (SD <0.3) log10 cfu/ml. LSCM of baseline samples was positive for live biofilm in all groups. At the end of the study, viable biofilm was only present in the control. In the microbial challenge test, all vegetative organisms were killed within 30 seconds of contact, while spores were killed within 5 minutes. Corrosion was seen in metals used in US-manufactured dental unit materials, while not observed in those used in the Castellini Logos Jr dental unit. Conclusion In this study, the TAED perborate protocol was effective in biofilm control and control of dental treatment water contamination. Use of sterile water or 2 ppm ClO2 along with TAED treatment also controlled planktonic contamination effectively. Clinical significance Environmental biofilms contaminate dental unit water systems over time and affect the quality of dental treatment water. Contaminants include environmental biofilms, microbes, including gram-negative rods and endotoxins in high doses that are not of acceptable quality for treating patients. There are many germicidal protocols for treating this contamination and one such is the prescribed use of TAED perborate used in conjunction with sterile water for irrigation in the autosteril device, an integral component of the Castellini dental units for between patient decontamination of dental unit water systems. This study was conducted on an automated simulation dental unit water system to test the TAED perborate protocol's efficacy on naturally grown, mature environmental biofilms, it's efficacy on microbes and spores and it's effects on materials used in dental unit water systems. This translational research addresses both microbial control and material effects of TAED perborate in studying efficacy and possible deleterious effects and simulated use in dentistry. Currently, this antimicrobial use protocol is followed worldwide in the Castellini dental units that are used in day-to-day dental patient care. How to cite this article Puttaiah R, Svoboda KKH, Lin SM, Montebugnoli L, Dolci G, Spratt D, Siebert J. Evaluation of an Automated Dental Unit Water System's Contamination Control Protocol. J Contemp Dent Pract 2012;13(1):1-10.

The recent explosion in capability of embedded and portable electronics has not been matched by battery technology. The slow growth of battery energy density has limited device lifetime and added weight and volume. Passive energy harvesting from solar radiation, thermal sources, or mechanical vibration has potentially wide application in wearable and embedded sensors to complement batteries. The amount of energy from harvesting is typically small and highly variable, requiring circuits and architectures which are low power and can scale their power consumption with user requirements and available energy. We describe several circuit techniques for achieving these goals in signal processing applications for wireless sensor network nodes such as using Distributed Arithmetic to implement energy scalable signal processing algorithms. In addition, we propose increasing vibration energy harvesting efficiency by eliminating AC/DC conversion electronics, and have investigated self-timed circuits, poweron-reset circuitry, and memory for energy harvesting AC power supplies. These techniques can also be applied to energy harvesting from other sources. A chip will be fabricated to test the proposed circuits.